PAGE 1 STATE OF FLORIDA STATE BOARD OF CONSERVATION DIVISION OF GEOLOGY Robert O. Vernon, Director REPORT OF INVESTIGATIONS NO. 50 WATER RESOURCES OF ORANGE COUNTY, FLORIDA By W. F. Lichtler, Warren Anderson, and B. F. Joyner U. S. Geological Survey Prepared by the UNITED STATES GEOLOGICAL-SURVEY in cooperation with the DIVISION OF GEOLOGY, FLORIDA BOARD OF CONSERVATION and the BOARD OF COUNTY COMMISSIONERS OF ORANGE COUNTY Tallahassee. I.s. . PAGE 2 SCIENCE LtBRAft FLORIDA STATE BOARD E OF CONSERVATION CLAUDE R. KIRK, JR. Governor TOM ADAMS EARL FAIRCLOTH Secretary of State Attorney General BROWARD WILLIAMS FRED O. DICKINSON, JR. Treasurer Comptroller FLOYD T. CHRISTIAN DOYLE CONNER Superintendent of Public Instruction Commissioner of Agriculture W. RANDOLPH HODGES Director ii PAGE 3 LETTER OF TRANSMITTAL STATE BOARD QF CONSERVATION Division of Geology Tallahassee January 26, 1968 Governor Claude R. Kirk, Chairman State Board of Conservation Tallahassee, Florida Dear Governor Kirk: The Division of Geology of the Florida Board of Conservation is publishing as our Report of Investigations No. 50, a study of the water resources of Orange County, Florida, prepared by Lichtler, Anderson and Joyner of the U. S. Geological Survey. This report is a cooperative study between the Orange County Commission, the Division of Geology, and the U. S. Geological Survey. With the anticipated urban expansion of Orange County that will be accompanied with the development of Disney World, the water resources of the area must be adequate to meet the demands of an expansion that will change a swamp to an urban area in a space of five years. We feel that the water resources of Orange County are adequate to meet these demands and we are proud to be able to contribute in a substantial way to the development of the area. Respectfully yours, Robert O. Vernon Director and State Geologist ROV:lam iii PAGE 4 Completed manuscript received January 26, 1968 Printed for the Florida Board of Conservation Division of Geology By the E. 0. Painter Printing Company DeLand, Florida iv PAGE 5 CONTENTS Page Abstract ..............-...........--.---------------------...........-----------..... ---------1 Introduction ......----...------..-....---.......--------...-----...--......... 2 Purpose and scope of investigation ............--..........---.........--...............--3 Acknowledgments ---.......-...-..-...-...----------------..--..---.-.---.-.... 3 Previous investigations .............--......-..---..-..---------. ...--4 Well-numbering system ........-.........---..-----....--------....--....--.-.....--....--..... 5 Description of the area .....--..-------........-.. ----------..-------..-6 Location and extent ........................ ..... .................... ...-.......... ...--------6 Topography ---........ ----...---............................ ........ ........ .... 6 Climate ...................---------............ -------------------... 10 Sinkholes -... ---........-.......---... ......--------.. ----...--...... ........ 10 Drainage ---.... -------.......... .-------------.....-...-----. -..................... 14 Geology --...--....-----------.......--.--.-------------.---.------14 Form ations .................. .. ................................................. ................... .. 18 Structure .--........----..... ....... --.........----------.... .---------.. .22 Hydrology .......--...----......... ...---------------------------....... .............. ..... 23 Chemical quality of water .-..................-........----------....-.............-.... ----23 Relation of quality of water to use -..------. ..---..---. .................-------24 Domestic use ..........---..--..--..-....------------------.--------29 Agricultural use -....... -------------------....................--...--.30 Industrial use ----....-.......--.....---------------------........--.......---..-32 Surface water --...............-..........---------------.... --------...-..-...-..--32 Occurrence and movement .......----..........------------...-... 32 Variation ....-............---------..... ...........---------------..----33 Presentation of data ........-...---...-----------....----........----.....--.. 35 Surface drainage ------......-----..-------...-------........-------------.-43 Kissimmee River basin -............. -------------------------.. ......---.-45 Reedy Creek ---..--.--------------....----.....------.-----. 45 Bonnet Creek ...........-........---...-....-----------------.-----....-----47 Cypress Creek ......-................--------------------------------48 Shingle Creek -....-.......-..... ...........----------------..----.. ... 49 Boggy Creek -..--. -----.......---...... -...-.. --....................-----50 Jim Branch -...-------.......-..-.-...............-.. ................................. -------------52 Ajay-East Tohopekaliga Canal .........-----..-..__..--..-.----------..--52 St. Johns River basin .--...............---........ ----------...----------------. 53 St. Johns River .........-.. .........---------------..--------53 Small tributaries draining east ....--.....-.....--...----...-------...... 59 Lake Pickett ......----..........-..-.. ...-----------------------------------. 61 Econlockhatchee River ....-..--..-....-..------.. ---------..------.. 61 Little Econlockhatchee River .--. ------..--..............----.....-----------65 Howell Creek .-----.......--......-...-------------.---------------------67 Wekiva River .....--------------.............---------.........................................-------------------68 Apopka-Beauclair canal ....--.................----.-----------------------71 Lakes .-....-... ................-----.. .....----------...........--...-------------------------71 V PAGE 6 Occurrence -...-.--.........-... .....--... ............................... .........-............ 71 Surface area -....-.....-....--....--.......--..........--.... --. ..---.......-..--....-... 74 Depths .... ........ ...........--. -.-..-........ ..------------............. 74 Altitudes ..-.--.-........-.......-........-...........----....--...-..-... ..-........--.....----.... 74 Seasonal patterns in lake-level fluctuations .......................--.---..-..-..--.74 Range in lake-level fluctuations ....-..-..........--....----...-...-..-.......-...-.77 Water quality in lakes --..-.....-......--...-..-..----....----..-----78 Control of lake stages .---..--..----....--......--. -----------......--..-80 Problems ......------..-..........-...--...--.....---................--.-.......------. -----.....................---..... 81 Ground water ...-............................................-............................. ....-..-.................. 82 Nonartesian aquifers ---.........---.......... .........-------------........ 82 Water levels ................-..-..--....-...-...........-------.....---------..-..-. 83 Recharge ..--.......--..----..........-.-------..---------86 Discharge ..-----....-.-----..-...-...--.----..--..-..............-----86 Quality of water .---....---......-..-..-------... ...-..-..--..........----. -87 Secondary artesian aquifers .---...-.......-...--..--.. ........ -----88 Water levels ...-...---........ ..-----------.......-....------...-88 Recharge ..---........-..---.---....--------------..-.. 90 Discharge .--...---....----......---------------..-.---.....-....... 90 Quality of water -....-.--..-......... ..----------......--------------------..-...-... 90 Floridan aquifer ---......--.--... ...... ------.-------.. -......--..... 91 Aquifer properties ..---......-.... ...... ---....----.......--..-... 91 Zones of the aquifer ...-...-..-------....-------------------...... 94 Interrelation of zones ...-.----........ ---------------.......--.....-. 95 Piezometric surface .-------..._~.~. -..................-.-.. --101 Fluctuations ...------...........--------------..-......--.. .. -106 Recharge areas --.......----.... ---------------.----..------112 Discharge areas -..------............. ... ............. ...-..-....-......-.. ..116 Quality of water ...-......... .. .................................... .... ................ .. 117 Salt-water contamination ......_.......---.------------......-....-...--. 124 Drainage wells .--..-..--...-..-----....................----------------------------...............--..-..--.. 128 History .....--...--... --........... ...-...-............... ...................-.. 128 Pollution .---... ..... ----------------------.........-..... ............-.-128 Other aspects of drainage wells .-----...----.-........--....-----------... 133 Pum ping tests ....................................................... ....... ...... 134 Water use -------------------------------..................................... ...........-139 Ground water .--......-..------.~... .........-... ........ 139 Surface water .---------. ........---------------.... ..................... ....----.......-...... 142 Summary ---...................................................................----------------------------------------------------.................. 143 Conclusions ..-----.------... -------.........---------------........................ 145 References ...--........................................----------..... -----------------------------. 148 ILLUSTRATIONS Figure Page Frontispiece. Aerial view of the Orlando business district looking northward from Lake Lucerne ..---...........----------..........-......--..... Facing p. 1 1 Location of Orange County and illustrating well-numbering system 5 2 Location of inventoried wells other than drainage wells, Orange County, Florida .................................... ....-................----.................... 7 vi PAGE 7 3 Topographic regions of Orange County, Florida ....-.......................... 8 4 Sinkhole two miles west of Orlando formed in summer of 1953 ....... 12 5 Location of drainage wells in Orange County, Florida, 1964 ........ 15 6 Geologic sections --...-......... ..... ............................... ....... ....... Facing p. 14 7 Configuration and altitude of top of the Avon Park Limestone, Orange County, Florida ............... ........... ........ ................. ... .-........ 19 8 Configuration and altitude of top of the limestone of Eocene age, Orange County, Florida ..... .......-----. ...-.........-....... ....... --..-..---21 9 Annual average discharge and average discharge for period of record at three stations on streams draining from Orange County... 34 10 Annual rainfall at Orlando .-................ ................. ......... ...-.. 35 11 Average, maximum, and minimum monthly mean discharges of three streams draining parts of Orange County and rainfall at Orlando .................................................. .............. ... ...................... .36 12 Monthly runoff from Econlockhatchee River basin 1949 and 1958 .. 37 13 Type and duration of surface-water stage and discharge records and number of chemical analyses of surface water samples collected at gaging sites in and near Orange County .-..... -...._........38 14 Duration curves of daily flow for streams in and near Orange County ..................................----..--....-.................. .......... ...... 40 15 Estimated flow-duration curves for streams and springs for which periodic or miscellaneous discharge data are available ....--............ 41 16 Stage-duration curves for selected lakes ...............................--.. 42 17 Water-surface profiles for floods of selected recurrence intervals on main stem of St. Johns River in Orange County -....-..-.... .... 44 18 Drainage basins and surface-water data collection points .... Facing p. 44 19 Streambed profile for selected streams in the upper Kissimmee River basin ..-..-..-...---. .....-...... ........-------.... ....... ....... ... ... .......... 46 20 Streambed profiles of Boggy Creek and Jim Branch .............. ---..... 51 21 Flow-duration curve for Myrtle-Mary Jane canal near Narcoossee 53 22 Low-flow frequencies for St. Johns River near Christmas .............. 55 23 Chloride concentration in water in St. Johns River from U. S. Highway 192 to State Highway 16, northeastern Florida.................-.....-... 56 24 Specific conductance of water in St. Johns River near Cocoa ..-....-..57 25 Cumulative frequency curve for specific conductance of the St. Johns River near Cocoa, October 1953September 1963 .............--.. 58 26 Streambed profiles of small streams draining east into St. Johns River .-----......-..-...-.....---------------------...........---........------.---60 27 Streambed profiles of Econlockhatchee River and selected tributaries ---.-....-..----------.. -----.. ......--. ........-......-.......----........... ..... --62 28 Low-flow frequencies for Econlockhatchee River near Chuluota....... 64 29 Cumulative frequency curve of specific conductance of the Econlockhatchee River near Bithlo, October, 1959 -May, 1962 .-..--...-........65 30 Relation of specific conductance to hardness and mineral content for Econlockhatchee River near Bithlo -....-......-.......................---... --66 31 Estimated flow-duration curves for Howell Creek near Maitland ... 68 32 Streambed profiles for Wekiva River and tributaries....--....--..--........ 69 33 Low-flow frequencies for Wekiva River near Sanford --...-....-..---..-...-70 34 Estimated average monthly evaporation from lakes..............-------...---. 75 35 Comparison of average monthly change in stage of three lakes vii PAGE 8 with average monthly difference in rainfall and evaporation at Orlando -76 36 Hydrographs for wells near Bithlo and Hiawassee Road showing pattern of fluctuation of the water table 84 37 Relationship between water levels at Bithlo and rainfall at Orlando 89 38 Configuration and altitude of the top of the Floridan aquifer in Orange County, Florida___92 39 Depth below land surface to the top of the Floridan aquifer in Orange County, Florida _ __ _ 93 40 Distribution of reported cavities in Floridan aquifer in Orange County, Florida _______96 41 Relationship between water levels in the upper and lower zones of the Floridan aquifer at Orlando _ 97 42 Hydrograph of well 833-120-3 showing effects of pumpage in the Orlando well fields _ __ _ 98 43 Configuration and altitude of the piezometric surface in the lower zone of the Floridan aquifer in the Orlando area -99 44 Relation between dissolved solid and hardness of water depths of wells in the Orlando area __ _-_ 100 45 Piezometric surface and areas of artesian flow of the Floridan aquifer in Florida, July 6-17, 1961 __ _ 101 46 Contours of the piezometric surface at high-water conditions, September 1960 __ 102 47 Contours of the piezometric surface at about normal conditions, July 1961___ 103 48 Contours of the piezometric surface at about normal conditions,. December 11-17, 1963 ___ ____ 104 49 Contours of the piezometric surface at extreme low water conditions, May 1962 ____ 105 50 Piezometric surface relative to land surface datum, at high water conditions, September 1960, Orange County Florida .______ 107 51 Piezometric surface relative to land surface datum, at low-water conditions, May 1962, Orange County, Florida ___ --_ 108 52 Hydrographs of wells __-___ 109 53 Range of fluctuation of the piezometric surface from September 1960 to May 1962, Orange County, Florida _ 110 54 Recharge areas to the Floridan aquifer in Orange County, and selected adjacent areas, Florida __ Facing p. 112 55 Dissolved solids in water from wells that penetrate the Floridan aquifer, Orange County, Florida _ __ -114 56 Hardness of water from wells that penetrate the Floridan aquifer, Orange County, Florida 119 57 Chloride concentration in water from wells that penetrate the Floridan aquifer, Orange County, Florida -____ 120 58 Composition of mineral content of water from selected wells in the Floridan aquifer _----_ 123 59 Temperature of ground water in Orange County, Florida _125 60 General areas where bacterially polluted water has been reported from some wells. (After unpublished map prepared by Charles W. Sheffield, Orange County Health Department)___--130 viii PAGE 9 61 Location of wells used in salt test in Lake Pleasant area____ 131 62 Changes in population and water use_._ ___ 140 TABLE Table Page 1 Temperature and rainfall at Orlando, Florida .__. -11 2 Summary of the properties of the Geologic formations penetrated by water wells in Orange County _-----_ --_________.-------16 3 Altitudes of terraces in Florida _.__ 22 4 Water quality characteristics and their effects ____--------------25 5 Drinking water standards for fluoride concentration ._--30 6 Water quality requirements for selected uses _ Facing p. 32 7 Sites where miscellaneous surface-water data have been collected 39 8 Ranges in quality of surface water in Orange County __ Facing p. 40 9 Chemical analysis of St. Johns River water, June 7, 1962_ __ 57 10 Minor elements in water from St. Johns River near Cocoa, May 11, 1962 _ 59 11 Discharge measurements of springs in Orange County, Florida.__72 12 Analysis of water from Lake Francis and Spring Lake 79 13 Analysis of water from selected wells in the Floridan aquifer in Orange County, Florida ___ 122 14 Results of pumping tests in Orange County, Fla. 136 ix PAGE 10 Aerial view of the Orlando business district looking northward from Lake Lucerne. PAGE 11 WATER RESOURCES OF ORANGE COUNTY, FLORIDA By W. F. Lichtler, Warren Anderson, and B. F. Joyner ABSTRACT The population and industry of Orange County are expanding rapidly but the demand for water is expanding even more rapidly. This report provides information for use in the development and management of the water resources of the area. The county is divided into three topographic regions: (1) lowlying areas below 35 feet (2) intermediate areas betweeen 35 and 105 feet and (3) highlands above 105 feet. The highlands are characterized by numerous sinkholes, lakes and depressions. Surface runoff forms the principal drainage in the lowlying and intermediate regions, whereas underground drainage prevails in the highlands. Lakes are the most reliable source of surface water as swamps and most of the streams, except the St. Johns and Wekiva Rivers, go dry or nearly dry during droughts. Approximately 90 of the 1,003 square miles in Orange County are covered by water. The southwestern 340 square miles of the county drain to the south to the Kissimmee River. The remainder drain to the north to the St. Johns River. The water in the lakes and streams in Orange County generally is soft, low in mineral content, and high in color. The quality of the water in most of the lakes remains fairly constant except wnere pollution enters the lakes. Ground water is obtained from: (1) a nonartesian aquifer composed of clastic materials of late Miocene to Recent age; (2) several discontinuous shallow artesian aquifers in the Hawthorn Formation of middle Miocene age; and (3) the Floridan aquifer composed of limestone of Eocene age. The surficial nonartesian aquifer yields relatively small quantities of soft water that is sometimes high in color. The shallow artesian aquifers yield medium quantities of generally moderately hard to hard water. The Floridan aquifer is the principal source 1 PAGE 12 2 REPORT OF INVESTIGATIONS NO. 50 of ground water in Orange County. It comprises more than 1,300 feet of porous limestone and dolomite and underlies sand and clay deposits that range in thickness from about 40 to more than 350 feet. Most large diameter wells in the Floridan aquifer will yield more than 4,000 gpm (gallons per minute). Water levels of the Floridan aquifer range from about 15 feet above to more than 60 feet below the land surface. The quality of the water ranges from moderately hard in the western and central parts to saline in the extreme eastern part of the country. The Floridan aquifer in Orange County is recharged by rain mostly in the western part of the county. Drainage wells artificially recharge the Floridan aquifer, but may pollute the aquifer unless the quality of the water entering the wells is carefully controlled. Urbanization in the recharge area and pollution can reduce the amount of potable water available in the Floridan aquifer. Artificial injection of good quality surplus surface water can increase the amount of water available and improve its quality, especially in the eastern part of the county where there is salty water in the aquifer. Use of ground water in 1963 was estimated to average about 60 mgd (million gallons per day) for municipal, industrial, domestic and irrigational use. Use of surface water was estimated to be about 5.5 mgd for irrigation. Surface water was also used for cooling and recreation. INTRODUCTION The rapid increase of population and industry in Orange County and nearby areas has created a more than commensurate increase in the demand for water. Not only are there more people and more uses for water, but the per capita use of water is increasing. East-central Florida, as a growing center in missile development and space exploration, is increasing in population and industry; therefore, the increase in demand for water is expected to continue and even to accelerate. This report contains information on the quantity, chemical quality, and availability of water in Orange County. The report will be useful to people who have the responsibility of planning, developing, and using the water resources of Orange County and much of the East-central Florida region and to anyone interested in water. PAGE 13 WATER RESOURCES OF ORANGE COUNTY 3 PURPOSE AND SCOPE OF INVESTIGATION The purpose of this investigation is to furnish data that will be useful in the conservation, development, and management of the water resources of Orange County. Water is one of the most important natural resources and Orange County, with more than 50 inches of annual rainfall, hundreds of lakes, and the Floridan aquifer, is blessed with an abundant supply. However, the rainfall is not evenly distributed throughout the year, or from year to year, nor are there adequate storage reservoirs in all parts of the county. Knowledge of all factors affecting the water resources of an area is necessary in planning for the protection, efficient development, and management of water supplies. Recognizing this need, the Board of County Commissioners of Orange County entered into a cooperative agreement with the U. S. Geological Survey to investigate the water resources of Orange County. The investigation is a joint effort by the three disciplines within the Water Resources Division of the Survey under the direction of W. F. Lichtler, project leader. The report was prepared under the supervision of C. S. Conover, District Chief, Water Resources Division, Tallahassee. It is the comprehensive report of the 5-year investigation and also incorporates information contained in an interim report (Lichtler, Anderson, and Joyner, 1964), a lake-level control report (Anderson, Lichtler, and Joyner, 1965), a groundwater availability map (Lichtler and Joyner, 1966), and a surface-water availability map (Anderson and Joyner, 1966), produced as byproduct reports of the investigation. The report includes determinations of variation in lake levels, stream flow, chemical quality of surface and ground waters and ground-water levels, evaluation of stream-basin characteristics, delineation of recharge and discharge areas, investigation of characteristics of the water-bearing formations, assembly of water-use information and interpretations of water data. ACKNOWLEDGMENTS The authors express their appreciation to the many residents of Orange County who freely gave information about their wells and to various public officials, particularly the Board of County Commissioners, whose cooperation greatly aided the investigation. PAGE 14 4 REPORT OF INVESTIGATIONS NO. 50 Special appreciation is expressed to Fred Dewitt, County Engineer; to Robert Simon and Jesse Burkett of the City of Orlando Water and Sewer Department; and to L. L. Garrett and Gene Birdyshaw of the Orlando Utilities Commission for their assistance. Appreciation is given to the well drillers in and near Orange County who furnished geologic and hydrologic data and permitted collection of water samples and rock cuttings and measurements of water levels during drilling operations, and to the grove owners, managers and caretakers who furnished data on irrigational use of water. The Board of Supervisors of the Orange Soil Conservation District and Albert R. Swartz and other members of the technical staff of the U. S. Soil Conservation Service gave much useful advice and information and provided strong support and encouragement during the course of the investigation. PREVIOUS INVESTIGATIONS Two previous investigations of the water resources of Orange County have been made. A report by the U. S. Geological Survey (1943) gives the results of a study of lakes as a source of municipal water supply for Orlando. A detailed investigation by Unklesbay (1944) deals primarily with drainage and sanitary wells in Orlando and vicinity and their effect on the ground-water resources of the area. Other investigators have included Orange County in geologic and hydrologic studies. Fenneman (1938), Cooke (1939), MacNeil (1950), and White (1958) describe the topographic and geomorphic features of Central Florida. Cole (1941, 1945), Cooke (1945), Vernon (1951), and Puri (1953) describe the general geology of Central Florida and make many references to Orange County. Sellards (1908), Sellards and Gunter (1913), Matson and Sanford (1913), Gunter and Ponton (1931), Parker, Ferguson, Love, and others (1955), D. W. Brown, Kenner, and Eugene Brown (1957), and D. W. Brown and others (1962) discuss the geology and water resources of Brevard County. Stringfield (1935, 1956) and Stringfield and Cooper (1950) investigated the artesian water in peninsular Florida, including Orange County. Collins and Howard (1928), Black and Brown (1951), Wander and Reitz (1951), and the Florida State Board of Health (1961) give information about the chemical quality of water in Orange County. PAGE 15 WATER RESOURCES OF ORANGE COUNTY 5 WELL-NUMBERING SYSTEM The well-numbering system used in this report is based on latitude and longitude coordinates derived from a statewide grid of 1-minute parallels of latitude and meridians of longitude. Wells within these guadrangles have been assigned numbers consisting of the last digit of the degree and the two digits of the minute of the line of latitude on the southside of the quadrangle, the last digit of the degree and the two digits of the minute of the line of longitude on the east side of the quadrangle, and the numerical order in which the well within the quadrangle was inventoried. For example, well 827-131-3 is the third well that was inventoried in the 1-minute quadrangle north of 28027' north latitude and west of 81031' west longitude (See figure 1.). \ ~ i TIGEOR A -S'B 0 I • I. ' S, .r port t _ ---"T I »C -.. *\ --wik of longitArea of ' 4o ' 0' 5' 81 200' Lw 2 * s Wesll numb'r 827-e;-a. 2 " 1 8_.of t a31' merida of on u Well numbir 8 278 *-r, 3en I .-----Figure 1. Location of Orange County and illustration of well-numbering system. PAGE 16 6 REPORT OF INVESTIGATIONS No. 50 Wells referred to by number in the text can be located on figure 2 by this system. DESCRIPTION OF THE AREA LOCATION AND EXTENT Orange County is in the east-central part of the Florida peninsula (fig. 1). It has an area of 1,003 square miles of which about 916 square miles are land and about 87 square miles are water. It is bounded on the east by Brevard County, on the north by Seminole and Lake Counties, on the west by Lake County, and on the south by Osceola County. The estimated population of Orange County in 1963 was 290,000. In that year, the estimated population of Orlando, the largest city in the county, was 90,000 while Winter Park, the second largest city, had an estimated population of 20,000. The growth rate of Orange County's population has increased enormously since 1950 (See figure 63) and this trend is expected to continue. The population of Orange County is expected to reach 530,000 by 1975. The principal agricultural products in Orange County are citrus, ornamental plants, vegetables, cattle, and poultry. In 1960 there were about 67,000 acres of citrus groves, more than 600 nurseries and stock dealers, about 6,000 acres of vegetables-mostly in the Zellwood muck lands northeast of Lake Apopka-about 23,000 head of cattle and about 180,000 laying hens in the county. )J TOPOGRAPHY Orange County is in the Atlantic Coastal Plain physiographic province described by Meinzer (1923, pl. 28). The county is subdivided into three topographic regions: (1) the lowlying regions where altitudes are generally less than 35 feet; (2) -intermediate regions where altitudes are generally between 35 and 105 feet; and (3) highland regions where altitudes are generally above 105 feet. (fig. 3). The lowland regions include the St. Johns River marsh, the northern part of the Econlockhatchee River basin and the northeastern part of the county east of Rock Springs. Altitudes range from about 5 feet above msl (mean sea level) near the St. Johns River to about 35 feet above msl where there is a relatively steep scarp in many places in Orange County. The St. Johns River marsh PAGE 17 8Q45 40 V 3 26 20 05 S"Y os 81 SI i i i ii i i I I i i i i A r i ii i i t I r*3 LL LAK E 0 COUL TY N S4NGE COUNTY S' EXPLANATION 46 -46 Z .r r.... Ox angeCountyFlorida 40 -I ^ I L SEMI OLE ~?)S E M I N 0 LE -E I\ -.. "" " .-o N0 0 i A 4G .k C O U N T T \5' .0 22 " -10 C 0 U ~ .-4 Orange County, Florida, 21u Me ..i 'o sm An." 0.·. i: ··i u·..; ·J'! -~o d 1 4j A z Orange County, Florida. PAGE 18 w II I I I I I ' ! I I I I II I I i ! ! I I I I I I I S 40' .l' 2b. ' w' .Ii' ( ..0 6' 05 N' w5b " K * K E L A im a C 0 U NT Yi Y N hlow .kl0l4 w llIo '1 | | WI w 11eo I 4I 81 0 4:. --1-0 2 Lt o .e, L 0 _COUNTE 1 I. NN S4101 l, 1* 0@ I.41 I 5 ~ , # 6hen 6om U. S. 100 7 8 9 10 bo W." 19-)0011 0m 910100 0'WI 4d I"', , ' , , occ ..v. lopogrphic qu drongle , Fiure 3. Toorahic reions of Orane County. Florida. pi 30 I w5I z 441' , " " X ., , 1 t( .1 1 1 0Oi ofI -t,, 25 0 i POLK OS CEO" LA COUNTY I -0' COUNTY I s lken fnImn U.S. Geologic 0 I 2 ,3 54 6 7 9 O Sowy wopomp0 quodmnget Figure 3. Topographic regions of Orange County, Florida. PAGE 19 WATER RESOURCES OF ORANGE COUNTY 9 in the eastern part of the county is a part of Puri and Vernon's (1964, figure 6) Eastern Valley. The low area east of Rock Springs is a part of the Wekiva Plain and the Econlockhatchee Valley is a small part of the Osceola Plain. The intermediate region occupies most of the middle part of the county between the lowlands and the highlands. Altitudes range from 35 to 105 feet above msl but are mostly between 50 and 85 feet above msl. A characteristic area of ridges and intervening lower areas parallel the Atlantic coast is best developed in the area between Orlando and the Econlockhatchee River. These ridges are believed to be fossil beach ridges from higher stands of the sea. The intermediate region coincides, in general, with Puri and Vernon's (1964, figure 6) Osceola Plain except for the area in the northwestern part of the county which is a part of Puri and Vernon's Central Valley. The highlands occupy the western part of Orange County with an island outlier in Orlando and vicinity. Altitudes are generally above 105 feet but range from about 50 feet in low spots, such as the Wekiva River basin, to about 225 feet above msl near Lake Avalon on the western border of the county. The highlands contain many lakes and depressions, most of which do not have surface outlets. The highland regions in Orange County include parts of Puri and Vernon's Orlando Ridge, Mount Dora Ridge, and Lake Wales Ridge. The three topographic regions described above are approximately equivalent to the Pleistocene terraces postulated by MacNeil (1950) as the Pamlico terrace from about 8 feet to about 30 feet above msl, the Wicomico terrace from about 30 feet to about 100 feet above msl, and the Okefenokee terrace from about 100 to 150 feet above msl. Cooke (1939, 1945) has called the surface defined by the 42and 70-foot shorelines the Penholoway terrace and the surface defined by the 70and 100-foot shorelines the Wicomico terrace. The areas in Orange County that are above 150 feet probably are sandhills or altered remnants of higher terraces. The water resources of Orange County are directly related to the topography of the area. In general, the highlands are the most effective natural ground-water recharge areas. They have few surface streams but have many lakes and depressions. The intermediate region ranges from good to very poor as a groundwater recharge area. There are many lakes in some areas and none PAGE 20 10 REPORT OF INVESTIGATIONS No. 50 in others. Surface streams in this region either go dry or recede to very low flow after relatively short periods of drought. The lowlands are ground-water discharge areas and contain few lakes except in the mainstem of the St. Johns River. Streamflow is more sustained than in the other regions because of water stored in the lakes along the mainstem of the St. Johns River, spring flow, and seepage of ground water from both the water-table and artesian aquifers. CLIMATE Orange County has a subtropical climate with only two pronounced seasons-winter and summer. The average annual temperature at Orlando is 71.50F and the average annual rainfall is 51.4 inches. (See table 1.) Summer thunderstorms account for_ most of the rainfall. Thunderstorms occur on an average of 83 days per year, one of the highest incidences of thunderstorms in the United States (U. S. Weather Bureau, Annual Report 1960). SINKHOLES Sinkholes are common in areas such as Orange County that are underlain by limestone formations. Rainfall combines with carbon dioxide from the atmosphere and from decaying vegetation to form weak carbonic acid. As the water percolates through the limestone, solution takes place and cavities of irregular shape are gradually formed. When solution weakens the roof of a cavern to the extent that part of it can no longer support the sandy overburden, sand falls into the cavity and a sinkhole forms on the surface. (See figure 4.) Most of Orange County's natural lakes, ponds, and closed depressions probably were formed in this manner. Sinkholes range in size from small pits a few feet in diameter to large depressions several square miles in area. Large depressions are usually formed by the coalescence of several sinkholes. Sinkholes may form either by sudden collapse of a large part of the roof of a large cavern or by gradual infiltration of sand through small openings in the roof of the cavity. The latter condition is illustrated by the formation of a sinkhole in Canton Street in Winter Park in April 1961. The sink was first noted as a depression in the graded road. By the following day a hole about 6 feet in diameter had formed. In the next 2 days the hole gradually PAGE 21 TABLE 1. TEMPERATURE AND RAINFALL AT ORLANDO, FLORIDA Normal Normal Maximum Minimum daily daily Normal Normal rainfall3 rainfalls maximum minimum average rainfall temperature temptemperas e2 temperature1,2 inches12, Inches Year Inches Year January 70.7 50.0 60.4 2.00 6.44 1948 0.15 1950 February 72.0 50.7 61.4 2.42 5.64 1960 0.10 1944 o March 75.7 54.0 64.9 3.41 10.54 1960 0.16 1956 April 80.5 59.8 70.2 3.42 6.18 1953 0.28 1961 May 85.9 66.2 76.1 3.57 8.58 1957 0.43 1961 June 89.1 71.4 80.3 6.96 13.70 1945 1.97 1948 July 89.9 73.0 81.5 8.00 19.57 1960 3.83 1963 August 90.0 73.5 81.8 6.94 15.19 1953 3.20 1960 September 87.6 72.4 80.0 7.23 15.87 1945 1.65 1958 October 82.6 65.3 74.0 3.96 14.51 1950 0.46 1963 November 75.6 56.2 65.9 1.57 6.39 1963 0.09 1950 December 71.6 51.2 61.4 1.89 4.30 1950 Trace 1944 Yearly 80.9 62.0 71.5 51.37 68.74 1960 39.61 1943 SAverage for 10 or more years. "U. S. Weather Bureau records, 1931-60. 3U. S. Weather Bureau records, 1943-60. PAGE 22 **3 9 ·"4 0 Figure 4. Sinkhole .miles west of Orlando formed in summer 1953. It was A... bsequently fillod in and no further s-nkin4 has oceeurd. bi,.J,:W.' .~ T ~ ., .. ...,.. ... .. ... .... .. t ~' z a" Pc~I r1~i~ilV ',,'; E ,g·~· ~0 "p" Figure ·! 4. Snhl ie eto radofi'e nsrne 93 I a : Ihe~unl fJ:IFslle in an nofihiqniIhsOcl PAGE 23 WATER RESOURCES OF ORANGE COUNTY 13 increased in size to about 60 feet in diameter and to about 15 feet in depth. The hole was filled and no further development has been noted. Another sinkhole formed in 1961 in Pine Hills, west of Orlando. A depression about 1-foot deep and 50 feet in diameter that formed on April 23 and 24 was marked only by a faint line in the sand except where the outer edge intersected two houses. The floor of one room, the carport, and the concrete driveway of one house were badly cracked. The corner of the other house dropped about 6 inches. The slow rate of settlement was probably caused by a gradual funneling of the overlying sand and clay into relatively small solution channels in the limestone. The channels eventually became filled and the subsidence ceased. A sinkhole formed rather rapidly in Lake Sherwood on May 22, 1962. This spectacular sinkhole removed a section of the westbound lane of Highway 50 and about 3,000 cubic yards of fill were required to repair the damage. According to eye witnesses, the sinkhole formed over a period of about 2 hours. Sinkholes are most likely to form in areas of active groundwater recharge because the dissolving action of the water is greatest when it first enters the limestone aquifer. As the slightly acid water moves through the aquifer, it gradually reacts with the limestone and is neutralized. The prevalence of sinkholes is usually a good indication that the area is, or was in the past, an area of active recharge. Sinkholes can either improve or impede the recharge efficiency of an area. In some instances, sinkholes breach the semipervious layers that separate the surface sand from the aquifer and permit water to enter the aquifer more readily than before. In other instances, lakes that form in sinkholes become floored with relatively impermeable silt, clay and organic material which retards the downward movement of water. Much remains to be learned about the solution of limestone by water. Caverns have been discovered several thousand feet below the surface, and evidence indicates that active solution is going on at these depths. Present and future research by the U. S. Geological Survey and other agencies should provide much useful information about this important subject and its relation to ground-water movement and availability. PAGE 24 14 REPORT OF INVESTIGATIONS No. 50 DRAINAGE The eastern and southern parts of Orange County areAdainced princpally_by._urface streams. The St. Johns River and its tributaries drain the eastern and nol rei parf he countywhile SbhngleCreek Reed ree, Boggy Creek, and canals in the uppert Kissimmee River-basin drain mostof the south-central and southwestern pa;rtsof-the comunty._ Mxy swa slouiocur in the eastern and-southernpartsptf the-county because.of the poorly developed-drainage. Surface drainage in the western and northwestern partsof the county is mostly-intcloTIed depresi'is where if--itfer seeps into the ground or evaporates. A few sinliholes iniThis area have open connections with solution channels in the underlyingimestoniie-Wa-er -at collects in these sinkholes drains directly into thesolution channels. Most of the sinkholes, however, are floored with relatively impermeable sediments and the rate of seepage through these lake-filled sinkholes may be less than in areas adp'cent to the lakes. "More than 300 drainage wells weredriled-hetween 1906_and 1961 in the upland area of the ountyespecially in Orlando and vineity, to dransurface water directly into the artien quifeiifadii ' ---;-the__ rifidai&!0ý7ý-jqife_ (fig. 5)The greatest activity was during 1960 when about 35 drainage wells were drilled. Considerable quantities of wate-are drained underground in this manner, but the total amount is not Izi-6wn. e ater that entersls-e-aquifer through drainage ll ranges fro urwater used to Aush cow arns. GEOLOGY The occurrence, movement, availability,'.quality, and quantity of the ground water in Orange County are 'closely related to the geology of the area. Therefore, knowledg of the structure, stratigraphy, and lithology of the geologic formations is essential to an evaluation of the ground-water resources. ---Orange County is underlain mostly by marine limestone, dolomite, shale, sand, and anhydrite to about 6,500 feet at which depth granite and other crystalline rock of the basement complex occur. Only the top 1,500 feet of sediments that have been penetrated by water wells will be discussed in this report. A summary of the properties of the formations is given in table 2. PAGE 25 A A C C T CIO < , , , .T--o T D T EXPLANATIO N Coo C t o co co To CO Crocoor N) 0-d f 1 00 00 o LITHOLOGY r o o o oo 3 o 00 o 200 S1 0" -I00 Shell 200 :: : * *-.n... S E A S LEVEL Marl ....... ...... 400 400 Limestone Dolomite S6 G EO LOG Y -1100 S:::.::::. .. C LO .SEA O Sediments 100 orn 2 .0 .. ...:.... 200 Ocala Group 00 300 -..400 Limestone 00 0 10 20 30 40 miles 400 Vertical exaggeration x 264 DoomitFigure 6. Geologic sections. Fiog u r co Geologi sections. PAGE 26 845' 40 35' 30' 25' 20' 15' i 05' B0o' 55' 80. 28°50' II I I I I 28*50 N LA KE COUNTY -EXPLANATION /J " 'I ,1' :W 4 ->_ Dreinage C.Nd -4o40 0 0 " ,. • ' .' NOLE Loke 0RANG ApopA C 0 U N T Y O 1 %. .L -. .-.-.---S C EO A U N T Y S..W .I 8 K -250' i -L o a w 81'45 40' 35' 30' 25 20' 5' 10' 05' 8100' 55' 80'50' Base token from U.S GeologIcol O I 2 3 4 5 6 7 8 9 10 mOtes Survey topographic quadrangles Figure 5. Location of drainage wells in Orange County, Fla., 1964. PAGE 27 TABLE 2. SUMMARY OF TIE PROPERTIES OF THE GEOLOGIC FORMATIONS PENETRATED BY WATER WELLS IN ORANGE COUNTY, FLORIDA Thickness, Formation in Description of Water-bearing Series name feet material properties Aquifer Water level UndifferRecent and entiated, may inMostly quartz sand Varies widely in 0 to 20 feet below Pleistocene elude 0-200 with varying quantity and qualNon-artesian the land surface Caloosaamounts of clay and ity of water probut generally less od hatchee shell. duced. than 10 feet. Pliocene(?) Marl Piezometric surGray-green, clayey, Shallow arteface not defined, quartz sand and silt; Generally impersian, lower water level geno phosphatic sand; meable except for limestone beds erally is lower Miocene Hawthorn 0-200 and bu.T, impure, limestone, shell, may be part of than nonartesian phosphatic limestone, or gravel beds. Floridan aquiaquifer and higher o mostly in lower part. fer. than Floridan aquifer. o Cream to tan, fine, Moderately high soft to medium hard, transmissibility, Ocala 0-125 granular, porous, most wells also Group sometimes dolomitic penetrate underlimestone. lying formations. PAGE 28 TABLE 2 CONTINUED Upper section mostOverall transmisly cream to tan, sibility very high, granular, porous contains many inlimestone. Often conterconnected soPiezometric surAvon 400tains abundant conelution cavities. Floridan face shown in figEocene Park 600 shaped Foraminifers. Many large capaures 10 and 11. Limestone Lower section mostly city wells draw dense, hard, brown, water from this crystalline dolomite, formation. o Lake Over Dark brown crystalSimilar to Avon City 700 line layers of doloPark Limestone. Limestone Total mite alternating with Municipal supply m unchalky fossiliferous of City of Orknown layers of limestone. lando obtained from this formation. I-A PAGE 29 18 REPORT OF INVESTIGATIONS NO. 50 Geologic sections showing the formations and types of material are shown in figure 6. FORMATIONS The oldest formation penetrated by water wells in Orange County is the Lake City Limestone of middle Eocene age (about 50 million years old). The Lake City Limestone consists of alternating layers of hard, brown, porous to dense, crystalline dolomite and soft to hard, cream to tan, chalky, fossiliferous limestone and dolomitic limestone. The Lake City Limestone is distinguished from the overlying Avon Park Limestone by the presence of the fossil Dictyoconus americanus; however, in Orange County, the rock in the depth interval (about 600-900 feet) where the top of the Lake City would normally be has been partly crystallized and the fossils have been badly damaged. Therefore, the exact location of the top of the formation is unknown. No water wells penetrate the total thickness of the Lake City, but the formation is probably more than 700 feet thick. The Avon Park Limestone conformably overlies the Lake City Limestone and is composed of similar materials. The formation is distinguished from overlying formations by the occurrence of many sand-sized cone-shaped foraminifera. In many areas, the Avon Park is composed mostly of the shells of these tiny singlecelled animals. Contours on the top of the Avon Park Limestone are shown in figure 7. The thickness of the Avon Park is not accurately known because only a few wells penetrate the formation and the contact with the underlying Lake City Limestone is indistinct, but the Avon Park is probably 400 to 600 feet thick. The Ocala Group' of the Florida Geological Survey overlies the Avon Park Limestone and contains the Crystal River, Williston, and Inglis Formations of late Eocene age. The limestone of the Ocala Group in Orange County was deeply eroded and in some areas entirely removed before the overlying formations were 'The term "Ocala Group" has not been adopted by the U. S. Geological Survey. The Florida Geological Survey uses Ocala as a group name as proposed by Puri (1953) and divided into three formations-Crystal River, Williston and Inglis Formations. PAGE 30 S5.' '40 35' 3d 25 .d 2 i Os erod s5' e sed 1a1 dI I I I I I I I I I I I I I I I I¶ I I0 I I I I 1 1 2 _O f rr:rm eOJ "t , ".' c ' -, I. , r "'l L"rrtfc"".' .rcqf c (IIc'" O9r N ORANGE COUY--*o45" ! , J .,--l ,r 1 ' 525 w *4* 0 ' fly co U r r 1.0' P o' 5' 2O' Co |,,r t O in rdriPrs M c rl c1a 40 m tr -| 4 -6s oO A 40~ -SEMINOLE.. I NI ISE T Ahe 0 ORANGv N0N C T 0 U N T Y 1 2 _10 C 0 U N T Y I aoIt oken -ro m US Geo logiol 0 I 2 3 4 5 6 7 8 9 00mi.$ 3 I o dOR LAuND o t0 Orange C , ldlCOUNTY I o L leh ' I Il l 28.17'. -.4o 8V45 40 3 30 20 6 a0 84 65 0W Boss Oake from U.S Geologcal o I a 3 4 5 6 7 6 9 1r0.n l0 Figure 7. Configuration and altitude of top of the Avon Park Limestone, Orange County, Florida. PAGE 31 20 REPORT OF INVESTIGATIONS No. 50 deposited. In south-central Orange County, formations of the Ocala Group are missing, but in the northeast part of the county near Bithlo the Ocala is about 125 feet thick. The contours on the top of the Eocene limestones in figure 8 show the eroded surface of the Ocala Group except where the Ocala is absent. In these areas the contours represent the top of the Avon Park. The Hawthorn Formation of Miocene age (about 25 million years old) unconformably overlies the Ocala Group and, where the Ocala is missing, the Avon Park Limestone. The clayey sand of the Hawthorn Formation retards the vertical movement of water between the water-table aquifer and the underlying limestone of the Floridan aquifer. In most parts of the county the Hawthorn retards, to varying degrees, the downward seepage of the water from the water-table aquifer. In low lying parts of the county where the artesian head is above land surface the Hawthorn Formation retards the upward movement of water. The lower part of the Hawthorn Formation usually contains more limestone than the upper part. The limestone sections usually contain much phosphorite and quartz sand and may grade into sandstone known locally as "salt and pepper rock." In the northwestern part of the county, the Hawthorn Formation has a higher percentage of limestone than in the southeastern part. Orange County lies in the intermediate/zone between the limestone-clay type of Hawthorn in north-central Florida and the clay-sand type of Hawthorn in south-central and southern Florida. In Orange County the contact between the Hawthorn Formation and the underlying Eocene limestone is usually quite distinct; but the contact with the overlying deposits is gradational. The top of the Hawthorn is usually placed at the first occurrence of appreciable quantities of phosphorite or where a distinct and persistent greenish color appears. The Hawthorn is thickest (about 300 feet) in the southeastern part of Orange County and thinnest (about 50 feet) in the northwestern part of the county. Undifferentiated sediments above the Hawthorn Formation may include the Caloosahatchee Marl (which has been designated Upper Miocene, Pliocene or Pleistocene by various workers)2; thick deposits of red clayey sand which occur near the surface in some areas in western Orange County; and marine terrace deposits. The red clayey sand is used extensively in road building. 2The U. S. Geological Survey gives its age as Pliocene. PAGE 32 S40 3 3l ' 20 3S Io 05 ' 1o1 s s W I I I I I r I , i I ; i , I II. I .I "" , '*-.,--" EXPLANATION -coo, LA E COU _ J ./ NTY" ; .'. '* ", N OR AOtSE COUNTY N "~ ar .n r '1 tu--." 1 N 45 -0 \w M a ' s.t M 45!Sa ri < *t i val. -Z, I M * In / '"" ' ' i B.r hi .i * c ' -rq 4d to .e 4 Ace., tro zwo S POL S C E 0 L A | ,.-. C 0 U N T Y | -0 _COUNTY OU 35IMP= w1 W 40 364 0 26 201 1t 0 0 Sm 60 5f Swvey totporgr hc quedrongie " .. rz Figure 8. Configuration and altitude of top of the limestone of Eocene age, Orange County, Florida PAGE 33 22 REPORT OF INVESTIGATIONS NO. 50 The marine terrace deposits consist mostly of loose unsorted quartz sand with varying amounts of organic matter and occasional seams of clay. These sediments are generally thought to have been deposited during interglacial times of the Pleistocene ice age when sea level was higher than it is at present. Table 3 gives the altitude of the more prominent terraces as defined by Cooke. Only the Pamlico terrace with a shoreline at about 30 feet and the Wicomico terrace with a shoreline at about 100 feet are well developed in Orange County. The altitudes in Orange County above 100 feet represent eroded remnants of the higher Okefenokee and Coharie terraces or sand dunes formed during higher stands of the sea. TABLE 3. ALTITUDES OF TERRACES IN FLORIDA. Brandywine 270 feet Coharie 215 feet Sunderlahd 170 feet Wicomico 100 feet Penholoway 70 feet Talbot 42 feet Pamlico 25 feet Silver Bluff 5feet STRUCTURE The surface-of the limestones of Eocene age is shown in figure 8. This represents approximately the land surface as it was in post-Eocene/pre-Miocene time after a long period during which the limestone was above sea level and exposed to erosion. Figure 8 is one interpretation of limited data, and future studies based on more complete information and regional interpretation may result in drastic revision. For example, a steep-walled trough is shown in the southeastern part of the county, whereas actually there may be a fault in the St. Johns River valley as indicated on the geologic section in figure 6. Figure 7 shows contours on the top of the Avon Park Limestone. The top of the Avon Park Limestone appears smoother than the top of the overlying Ocala Group and was probably not eroded except where the Ocala is missing. Therefore, the Avon Park Limestone probably more nearly represents the regional dip of shallow limestone formations underlying Orange County. PAGE 34 WATER RESOURCES OF ORANGE COUNTY 23 The irregularities in the surface of the Eocene limestone may have been caused by deep erosion, but the contours on the top of the Avon Park Limestone strongly suggest a fault in the St. Johns River valley. Movement along this fault probably started in post-Eocene time and continued into Miocene time. HYDROLOGY CHEMICAL QUALITY OF WATER All waters except distilled water contain dissolved materials in varying amounts. The type and amount of dissolved materials is influenced by many factors such as source, movement, geology, topography, climate, biological action, and cultural changes. Rain falling through the atmosphere picks up small quantities of dust particles, atmospheric gases, and windblown salts. In areas near the ocean, the amount of salts picked up by rain may be appreciable especially if it is blown inland from the ocean. In industrialized areas the atmosphere generally contains exhaust gases and particles that are readily picked up by rain. The type and amount varies with the industry. Rain may also pick up radioactive fallout from nuclear explosions. To date, however, the amount of radioactive materials in water has remained far below tolerable limits. When rain reaches the earth, it begins to dissolve or pick up in suspension varying amounts of the materials contacted. The carbon dioxide dissolved from the atmosphere and from decaying organic matteron the earth's surface react with the water to form a weak carbonic acid. Carbonic acid greatly increases the ability of water to dissolve inorganic materials especially limestone such as underlies Orange County. Surface water moves more rapidly than ground water, consequently, its time of contact with soils and rocks is shorter. This is one reason for lower mineralization in surface water than in ground water. Surface water is usually higher in color than ground water because surface water dissolves living and decaying organic materials that it contacts. Decaying organic matter consumes dissolved oxygen from the water and releases. carbon dioxide. When water percolates into the ground, the rate of movement is greatly reduced. When water percolates very far through soils PAGE 35 24 REPORT OF INVESTIGATIONS NO. 50 and rocks, any bacteria or color present will usually be removed. The fluctuations in the quality and temperature of ground water are smaller than in most surface-water bodies because of the long period of time required for ground water to percolate downward to the aquifer and then laterally through the aquifer to the point of discharge. Dissolved mineral constituents in water are usually reported in parts per million (ppm) (one unit weight of a constituent in a million unit weights of water). Hardness of water is caused by the presence of alkaline earth metals, mostly calcium and magnesium, and is expressed as an equivalent quantity of calcium carbonate. Specific conductance is a measure of the ability of water to conduct an electric current and may be used in estimating the dissolved mineral content. The most important dissolved constituents can usually be related to specific conductance (fig. 25). Color is expressed in units of the platinum-cobalt scale. The symbol pH is a measure of the acidity or alkalinity of a solution, and is expressed as the negative logarithm of the hydrogen-ion concentration. RELATION OF QUALITY OF WATER TO USE The amount and type of dissolved and suspended materials in water determines its value for a particular use. Water suitable for one use may be entirely unsatisfactory for another. For example, sea water is used for cooling purposes, whereas it is unsatisfactory for most other industrial use. Water used in the manufacturing of products such as high-grade paper and textiles must be very low in dissolved solids. Table 4 shows the more common characteristics of water quality. Some constituents in water can be removed inexpensively whereas other constituents can be removed only by expensive distillation. Hardness of water may be removed by the relatively simple and inexpensive ion-exchange method which replaces the calcium and magnesium with sodium from common table salt. Iron, color, and turbidity may be economically removed by flocculation, settling, and filtration. The removal of sodium, chloride, and sulfate is difficult and expensive. PAGE 36 TABLE 4. WATER-QUALITY CHARACTERISTICS AND THEIR EFFECTS. Constituent or property Source or cause Effects Silica (SiO) Dissolved from practically all Forms hard scale in pipes and boilers. Carried over in steam of rocks and soils, commonly less high pressure boilers to form deposits on blades of turbines. Inthan 30 ppm. High concenhibits deterioration of zeolite-type water softeners. trations, as much as 100 ppm, generally occur in highly alkaline waters. Iron (Fe) Dissolved from practically all On exposure to air, iron in ground water oxides to reddish-brown o rocks and soils. May also be precipitate. More than about 0.3 ppm stains laundry and utensils t derived from iron pipes, reddish-brown. Objectionable for food processing, textile processing, a pumps and other equipment, beverages, ice manufacture, brewing and other processes. U. S. More than 1 or 2 ppm of iron Public Health Service (1962) drinking-water standards state that O in surface waters generally iron should not exceed 0.3 ppm. Larger quantities cause unpleasant indicate acid wastes from taste and favor growth of iron bacteria. mine drainage or other sources. o Calcium (Ca) and Dissolved from practically all Causes most of the hardness and scale-forming properties of water; c Magnesium (Mg) soils and rocks, but especially soap consuming (see hardness). Waters low in calcium and magneZ from limestone, dolomite, and slum desired in electroplating, tanning, dyeing, and in textile manu4 gypsum. Calcium and magnefacturing. sium are found in large quantities in some brines. Magnesium is present in large quantities in sea water. ______ _____________ _ _ _ _ _ _ ___ t01 PAGE 37 TABLE 1 CONTINUED Constituent or property Source or cause Effects Sodium (Na) and Dissolved from practically all Large amounts, in combination with chloride, give a salty taste. Potassium (K) rocks and soils. Found also Moderate quantities have little effect on the usefulness of water for in ancient brines, sea water, most purposes. Sodium salts may cause foaming in steam boilers industrial brines, and sewage. and a high sodium content may limit the use of water for irrigation. -3 0 Bicarbonate (HCO,) Action of carbon dioxide in Bicarbonate and carbonate produce alkalinity. Bicarbonates of calJ and Carbonate (CO,) water on carbonate rocks such cium and magnesium decompose in steam boilers and hot water as limestone and dolomite, facilities to form scale and release corrosive carbon-dioxide gas. In combination with calcium and magnesium, cause carbonate hardness. Sulfate (SO4) Dissolved from rocks and soils Sulfate in water containing calcium forms hard scale in steam containing gypsum, iron sulboilers. In large amounts, sulfate in combination with other ions 0 fides, and other sulfur comgives bitter taste to water. Some calcium sulfate is considered beneW pounds. Commonly present in ficial in the brewing process. USPHS (1962) drinking water standz mine waters and in some inards recommend that the sulfate content should not exceed 250 ppm. P dustrial wastes. Chloride (Cl) Dissolved from rocks and In large amounts in combination with sodium, gives salty taste to soils. Present in sewage and drinking water. In large quantities, increases the corrosiveness of found in large amounts in anwater. USPHS (1962) drinking-water standards recommend that cient brines, sea water, and the chloride content should not exceed 250 ppm. industrial brines. PAGE 38 TABLE 4 CONTINUED Constituent or property Source or cause Effects Fluoride (F) Dissolved in small to minute Fluoride in drinking water reduces the incidence of tooth decay quantities from most rocks when the water is consumed during the period of enamel calcificaand soils. Added to many tion. However, it may cause mottling of the teeth, depending on the waters by fluoridation of muconcentration of fluoride, the age of the child, amount of drinking nicipal supplies, water consumed, and susceptibility of the individual. (Maier, F. J., 1950, Fluoridation of public water supplies, Jour. Am. Water Works Assoc., vol. 42, pt. 1, p. 1120-1132). Nitrate (NO,) Decaying organic matter, sewConcentration much greater than the local average may suggest m age, fertilizers, and nitrates pollution, USPHS (1962) drinking-water standards suggest a limit d in soil. of 45 ppm. Waters of high nitrate content have been reported to be the cause of methemoglobinemia (an often fatal disease in inw fants) and therefore should not be used in infant feeding. Nitrate has been shown to be helpful in reducing inter-crystalline cracking of boiler steel. It encourages growth of algae and other organisms 0 which produce undesirable tastes and odors. Dissolved solids Chiefly mineral constituents USPHS (1962) drinking-water standards recommend that waters dissolved from rocks and soils. containing more than 500 ppm dissolved solids not be used if other Includes some water of crysless mineralized supplies are available. Waters containing more tallization. than 1,000 ppm dissolved solids are unsuitable for many purposes. Hardness as CaCO, In most waters nearly all the Consumes soap before a lather will form. Deposits soap curd on , hardness is due to calcium and bathtubs. Hard water forms scale in boilers, water heaters, and magnesium. All of the metalpipes. Hardness equivalent to the bicarbonate and carbonate is lications other than the alkali called carbonate hardness. Any hardness in excess of this is metals also cause hardness. called non-carbonate hardness. Waters of hardness up to 60 ppm are considered soft; 61 to 120 ppm, moderately hard; 121 to 180 ppm, hard; more than 180 ppm, very hard. PAGE 39 TAIILE -CONTINUED t 00 Constituent or property Source or cause Effects Specific conductance Mineral content of the water. Indicates degree of mineralization. Specific conductance is a meas, (micromhos at 250C) ure of the capacity of the water to conduct an electric current. Varies with concentration and degree of ionization of the constituents. Hydrogen ion Acids, acid-generating salts, A pH of 7.0 indicates neutrality of a solution. Values higher than concentration (pH) and free carbon dioxide lower 7.0 denote increasing alkalinity; values lower than 7.0 indicate the pH. Carbonates, bicarbonincreasing acidity. pH is a measure of the activity of the hydrogen ates, hydroxides, and phosions. Corrosiveness of water generally increases with decreasing phates, silicates, and borates pH. However, excessively alkaline waters may also attack metals. raise the pH. Color Yellow to brown color of some Water for domestic and some industrial uses should be free from waters is usually caused by perceptible color. Color in water is objectionable in food and organic matter extracted from beverage processing and many manufacturing processes. The > leaves, roots, and other orUSPHS (1962) states that color should not exceed 15 units in ganic substances. Objectiondrinking water. 0 able color in water also results M from industrial waste and sewage. Hydrogen sulfide Probably the reduction of sulCauses "rotten-egg" odor and causes corrosion. Limits of tolerance o (H.S) fates to sulfides by organic are generally less than 0.5 ppm. Since hydrogen sulfide is a gas material under anaerobic conit is easily removed from water by aeration. ditions in deep wells. In some cases, it may be derived from the anaerobic reduction of organic matter with which the water comes in contact. PAGE 40 WATER RESOURCES OF ORANGE COUNTY 29 DOMESTIC USE Water used for human consumption should be pathologically safe, low in turbidity and color, and free from taste and odor. Federal drinking water standards were first established in 1914 to control the quality of water used on interstate carriers and for culinary purposes. These standards have been revised several times, most recently in 1962 by the U. S. Public Health Service. They have been endorsed by the American Water Works Association as minimum standards for all public water supplies. Some of the U. S. Public Health Service's recommended limits for the various dissolved constituents and physical properties are given under the column of effects in table 4. Following are additional U. S. Public Health Service's recommended limits for dissolved chemical substances in drinking water. Substance Concentration (ppm) Alkyl Benzene Sulfonate (ABS) 0.5 Arsenic (As) 0.01 Copper (Cu) 1 Carbon Chloroform Extract (CCE) 0.2 Cyanide (Cn) 0.01 Fluoride (F) See table 5 Manganese (Mn) 0.05 Phenols (CGH,OH) 0.001 Zinc (Zn) 5 The U. S. Public Health Service states that the presence of the following toxic substances, in excess of concentrations listed shall constitute grounds for rejection of the supply for drinking water: Substance Concentration (ppm) Arsenic (As) 0.05 Barium (Ba) 1.0 Cadmium (Cd) 0.01 Chromium (Hexavalent) (Cr+G) 0.05 Cyanide (CN) 0.2 Lead (Pb) 0.05 Selenium (Se) 0.01 Silver (Ag) .05 PAGE 41 30 REPORT OF INVESTIGATIONS NO. 50 Unpolluted water rarely contains excessive concentrations of the above toxic substances. In highly industrialized areas, objectionable amounts of toxic substances are sometimes found in water. Two samples, one from the St. Johns River at low flow and the other from a typical Orlando supply well, were analyzed for minor elements. The cadmium, chromium and lead concentrations were less than .0014 ppm. The U. S. Public Health Service's standards for fluoride in drinking water are based on climatic conditions, because children drink more water in warmer climates and, consequently, consume more fluoride. Table 5 lists the drinking water standards for fluoride concentration. Where fluoride occurs naturally in water, it should not exceed the upper limit in table 5. Where fluoridation is practiced by water treatment plants, the concentration should be held between the lower and upper limits. The U. S. Public Health Service states that the presence of fluoride concentrations more than twice the optimum values in table 5 constitutes grounds for rejection of the supply. The yearly normal maximum daily temperature in Orange County is 80.90 F; therefore, the optimum amount of fluoride in drinking water is 0.7 ppm and the concentration should not be below 0.6 ppm or above 0.8 ppm. Fluoride concentrations in Orange County water are usually less than 0.8 ppm and often less than 0.4 ppm. AGRICULTURAL USE The primary non-domestic uses of water on the farm are for livestock consumption and for irrigation. The quality standards of TABLE 5. DRINKING WATER STANDARDS FOR FLUORIDE CONCENTRATION. Yearly normal maximum Recommended fluoride control daily temperatures oF limits in ppm Lower Optimum Upper 50.053.7 0.9 1.2 1.7 53.858.3 0.8 1.1 1.5 58.463.8 0.8 1.0 1.3 63.970.6 0.7 0.9 1.2 70.779.2 0.7 0.8 1.0 79.390.5 0.6 0.7 0.8 PAGE 42 WATER RESOURCES OF ORANGE COUNTY 31 water for human consumption have already been discussed. Very little information is available on quality of water standards for livestock watering, but it is assumed that water safe for human consumption is safe for animals. In general, animals can tolerate higher mineralization than man. The Department of Agriculture and Government chemical laboratories of Western Australia list the following limits for dissolved solids in ppm: Poultry 2,860 Pigs 4,290 Horses 6,440 Cattle, dairy 7,150 Cattle, beef 10,000 Adult sheep 12,900 Investigators have found that water with a dissolved-solids content of more than 15,000 ppm is dangerous if used continuously for livestock watering. The water from the Floridan aquifer in eastern Orange County is the most highly mineralized. The water from a few wells exceeds 3,000 ppm in dissolved solids but none exceed 4,000 ppm. The chemical quality of water is important in evaluating its usefulness for irrigation. The quality requirements for irrigation varies with the nature and composition of the soil and subsoil, topography, quantity of water used and method applied, climate, and type of crops grown. Good soil drainage is important where irrigation is practiced. Water of good quality for irrigation may not produce good crops on poorly drained land, whereas highly mineralized water may often be used successfully on open-textured well-drained soils. There is much published material on the quality requirements of irrigation water for various crops grown under varying conditions. U. S. Department of Agriculture Circular 969 entitled, "Classification and Use of Irrigation Water" by L. V. Wilcox (1955), classifies irrigation water based on electrical conductivity in micromhos/centimeter. The dividing point between four classes is 250, 750, and 2,250 micromhos. Wilcox points out that ". .. in classifying an irrigation water, it is assumed that the water will be used under average conditions with respect to soil texture, infiltration rate, drainage, quantity of water used, climate, and salt tolerance of the crop." All water in Orange County is suitable for irrigation. The artesian water in the eastern part is high in PAGE 43 32 REPORT OF INVESTIGATIONS NO. 50 mineralization, but because of adequate flushing during-the rainy season it is used successfully. INDUSTRIAL USE Water quality requirements for industry are so varied that it is impossible to set standards to meet the demands of all users. For some purposes, such as cooling, water of poor quality is often used when better quality water is not available. Water for some processes and for use in high-pressure steam boilers must approach the quality of distilled water. In general, most industrial water should be low in dissolved solids, soft, uniform in quality and temperature, and noncorrosive. Table 6 gives the quality requirements for several selected industries. The greatest industrial use of water in Orange County is for citrus processing and canning. (See section on use of water.) With a minimum of treatment most of the water in the county is suitable for most industrial uses. SURFACE WATER OCCURRENCE AND MOVEMENT Most of the surface water in Orange County is from rain within the county, but some flows into the county from adjacent areas of higher elevation. Some of the streams that provide water, such as the St. Johns River, also drain parts of Orange County. The amount of water on the land surface is determined by climate, geology, and topography. Only part of the rainfall remains on the surface long enough to be useful. Losses by evaporation and infiltration begin immediately and continue indefinitely unless the supply becomes exhausted. Some of the water that infiltrates into the soil and to the aquifers returns to the surface as seepage or as spring flow into lakes and streams. The part of the rain that doesn't evaporate or infiltrate collects in topographic depressions to form lakes, swamps, and marshes, or enters a stream channel and flows out of the county. It is estimated that about 70 percent of the rain that falls on Orange County returns to the atmosphere by evaporation and transpiration, about 20 percent flows out of the county in streams and about 10 percent flows out underground. PAGE 44 TABLE 6. WATER QUALITY REQUIREMENTS FOR SELECTED USES1 (Allowable limits in parts per million) aC4 >b -o r 0 Use o ( " Q S Other requirements2 Air Conditioning ---0.5 --low 1 ------No corrosiveness, slime formation rking 10 10 _ .2 _ _ low .2 0 ---P Boiler feed water -150 PSI 20 80 80 _ 3000-500 _ _ 5 40 50 200 8.0 150-250 PSI 10 40 40 _ 2500-500 _ _ 3 20 30 100 8.4 --250-00 tPSI 5 10 10 _ 1500-100 --0 5 5 40 9.0 --Oer 400 PSI 1 2 2 -50 --0 1 0 20 9.6 -_ Brewing Light beer 0-10 0-10 _ .1 500-1500 75-80 low .2 50 -50-68 6.5-7.0 10 60-100 100-200 30 -_ P NaC1 less than 275 ppm Dark beer 0-10 0-10 _ .1 500-1500 80-150 low .2 50 -50-68 6.5-7.0 10 60-100 200-50 30 P NaC1 less than 275 ppm Carbonated Beverages 12 5-10 200-250 0.1-0.2 850 50-128 low 0-0.2 --_ _ _ 250 -250 0.2-1.0 P Coanfetionary ---0.2 50-100 _ low .02 --_ 7.9 -.P No corrosiveness, slime formation Day industry 0 180 0.1-0.3 500 _ none ---. _ 17 30 _ _ 60 _ P Food Canning and Freezing 1-10 __ 350-85 0.2 850 30-250 none 1.0 7.5 8.6 400-600 _ _ 1.0 P Food Equipment washing 1 5-20 10 .2 850 _ none -1 -0 250 -: -1.0 P Food Processing, general 1-10 5-10 10-250 .2 850 30-250 low .5 -5 0 _ 6 -1.0 P Ice 15 5 _ .2 300 30-50 -_ 10 .---_ _ P Laundering --50 .2 ------Pastics, clear, uncolored 2 2 53 .02 200 ------__ tAmerican Water Works Association 1950 and Water Quality Criteria, McKee and Wolf 1963 "P indicates that potable water, conforming to USPHS standards, is necessary -Peas 200-400, fruits and vegetables 100-200, legumes 25-75 PAGE 45 WATER RESOURCES OF ORANGE COUNTY 33 VARIATION Part of the difficulty in managing the water resources of an area stems from variations in the amount of water stored on and beneath the earth's surface in the area. These variations are brought about because rainfall is extremely variable and intermittent, while evaporation, transpiration, surface outflow, and underground outflow though also variable are relatively continuous. Figure 9 shows the average discharge in cfs (cubic feet per second) per square mile for each year of record at three stations draining parts of Orange County. Figure 10 shows the annual rainfall at Orlando for this period. Comparison of these two figures reveals that the pattern of variations in runoff and rainfall are similar but not identical. The years of high flow agree well with the years of high rainfall and except for a 1-year attenuation of Wekiva River caused by depletion of ground-water storage, so do the years of low flow and low rainfall. Streamflow may average above normal during a year following a wet year because of the carry-over of storage from the wet year even though rainfall is below normal. After a severe drought, streamflow may average below normal and even decrease during a year of above-normal rainfall because of the large amounts of water required to replenish the depleted soil moisture before an excess to provide runoff becomes available. The flow of Wekiva River is much less variable than that of Econlockhatchee River and St. Johns River because it is maintained by the flow of large springs that discharge from a vast highly permeable ground-water reservoir (Floridan aquifer). The base flow of the Econlockhatchee and St. Johns Rivers is maintained mostly by seepage of water from the relatively thin and low yielding water-table aquifer. Their channels are very shallow so that a small drop in the water table causes a sharp reduction or cessation of ground-water inflow. Figure 11 shows that the distribution of monthly runoff during the year corresponds in a general way to the distribution of rainfall, but there are some apparent discrepancies. Although average rainfall for months March, April, May, and October is about equal, runoffs for these months differ widely. Average runoff decreases from March to May because evaporation and transpiration losses increase during this period (See fig. 41.). Runoff for October is higher than that for May because in October evaporation is less and storage, which increased during July, August, and September, PAGE 46 31 REPORT OF INVESTIGATIONS NO. 50 3 WEKIVA RIVER NEAR SANFORD Drainage area-200 sq. ni, approximately 2 Average-1.38 cfs per sq. mi. O w. 0a z 0 w ECONLOCKHATCHEE RIVER NEAR CHULUOTA w. Drainage area-260 sq. mi. S2 Average-1.06 cfs per sq. mi. w I 2.. -X 00 CO 3 w C ST JOHNS RIVER NEAR CHRISTMAS > Drainage area-1,418 sq. mi < p Average-0.98 cfs per sq. mi. S2z z Figure 9. Annual average discharge and average discharge for period of record at three stations on streams draining from Orange County. PAGE 47 WATER RESOURCES OF ORANGE COUNTY 35 70 U, S60z Normal z 50. -.. *: 51.37 in. 500 X S. ........ 40 Figure 10. Annual rainfall at Orlando. is released to the streams. There is some indication that this storage effect carries over into November. In a given year the distribution of flow for a particular station may differ markedly from that representing average conditions. Contrasting distributions of flow for Econlockhatchee River are shown in figure 12 for 2 years in which total runoff was about the same. PRESENTATION OF DATA The data used for this report were obtained during the period October 1935 to September 1963. If the physical conditions in the basin remain unaltered and no drastic changes in the climate take place, values for the next 28 years should be very similar to those for this period. The 28-year moving average of annual rainfall at Orlando beginning in 1893 has varied from the 71-year average by no more than 3.8 percent, indicating that conditions during < 0 i1:~:::: ····5~I::rii~:::::l::i5:~:;·::ii:P :x·st~ t4. ....... ....... ..... X ox .... ...~~''·:::~:~::: z :.:.: 2:l.:~i~i:~:~'~:.................cg~ Lo ... Ul) X..,.X.:: ~iI~~ii~iiii~::~ :iiIi:i~:i::·f; .::i::sI:SI~j:it~:~,:,,::.:~~:~~: ~ ~ L0 X 0):~;rziE: 30'~::::r:x~~~~~:::~~:: Figure 10. Annual rainfall at Orlando. is released to the streams. There is some indication that this :~x;,.,ii stoageeffct arresove ino Nvemer In agive yer th disribtionof fow or apartculr sttio may differ markedly from that representing average conditions.:~:~5 Contastig ditribtion of lowfor conlckhacheeRive ar show infigre 2 fr 2yeas i whih ttalrunff as bou th same.~i~~~i~:vi::: PRSETAIO O DT PAGE 48 ... 20 5 .::" o ..-0A:VEMAG ' U 10 A-,2 .5 1K V RI0 M IN IM U M V N M IN IM U M -A.10IN IM"Mo SST. JOHNS ERATNAL "1 RIVER AMTH jAV RA 0M' 00 .; ..:.R -I.VER NE AORLANDOi .0 MM JM Jz MAMJJASOND Figure 11. Average, maximum, and minimum monthly mean discharges of three streams draining parts of Orange County, and rainfall at Orlando. three streams draining parts of Orange County, and rainfall at Orlando. PAGE 49 WATER RESOURCES OF ORANGE COUNTY 37 4 ECONLOCKHATCHEE SRIVER NR. CHULUOTA WI Total 13.13 in. o 1958 i:iiiiii:: 7o , Z2 z UD 4 Total 13.85 in. ..3. i 1949 z 02 < I il < W < CL n M3 D LJ 0 0 Figure 12. Monthly runoff from Econlockhatchee River basin-1949 and 1958. the period October 1935 to September 1963 are representative of the long-term average. The average for the 28-year period 1936-1963 differed from the 71-year average by only 0.01 of 1 percent. The value of this report is premised on the applicability in the future of analyses based on past record. Surface-water data have been collected at 62 sites in the county. Data on the chemical quality of surface water have been collected at 35 of these sites since 1953. Figure 13 lists the sites where data have been collected systematically and shows the number of water samples analyzed, the types of stage and flow record collected, and the periods of record. Table 7 lists the sites where miscellaneous records have been collected. PAGE 50 38 REPORT OF INVESTIGATIONS NO. 50 oS Notof ion N i SStahion I hel --------a t I AdaCr Lake, ot Orlondo ; Aly-Eat TTahookealig Cn. n. Norcoossee 3 Apopka-oBeaucloar Canal at control nr Asfatula 4 oopklBeauclotar i at S.R. 448 nr Astatulo S.iopha, Lake, at Winter Garden 6 ata¶ Lake nr Orlando 7 Be-%e, Lake. at Windermere aB t Sand Lake ot Doctor Phillips *9 liqy Creek nr Kissimmee | in oi iy tCiek nr Tal It lBnlter Lake, a1 Windcrmere I ':iin>.Cd, Lake, t Orlando 10.1 orimny, Lake. >t Pne Castle 2 _3 3 4 *I LrrnLoke, nr Orlando 2 '.vore1s Creek at Vineland In ý%ton Cant!l nr Wewanottee 7'Ccr, LLak, at Mount Doro SE-olacknlocltutchee River nr Bthlo 34 -ca7loakhatchee H iver nr ChuluOtO 36 > ir Lekw, LkP, a Orlando SHarti La nr r'CJ 17o q ,uil .iru. L,:ke, a? Orl njd T 7T oniiti Ln1k,-. It 011i0n-O it4 .;, Creek nr Cier'ltmOa J5 onlns Lake at Oakland 4 6S I6ttle Econiackhtchee River nr, Union Park 25 T ;7 Little Lake Fairview at Orlando 13 Miotland. Lake, ot Winter Park 5 29 Mary Jone, Lake, nr NorcoOtsee 2 30 Mary Jane-Hart Canal nr Norcoossee ; IMyrtle-Mry Jane Canal nr Norcoossee 32 Park Lake ot Orlando i , Ponietl, Lake, nr COCOa 730 34 iRoweann, Lake, at Orlando J1 1r Johns River nr Christmas 47 36 St Jonns River nr. Cocoa 170 S1' St juhns River Flood Profile \k ShInile Creek of alrport, nr Kssimmee S1 'hiiylln Creek nr Vineland 22 4-1 _*iler, Lake, at Orlando -I 1 'aper, Lake, nr Orlando 4:' S3Qnq Luke at Orlando 43 Sut, Lake, at Orlando 44 Susarnnaht, Lake, nr Orlando 4 I 5,-ritili, Lake, oa Orlando .( Wiekci River nr Sanford 4r Wanonon (FronciS) Lake nr Plymouth 2 EXPLANATION Daily to weekly stage Monthly ;'aie or annual flood crest ....'4.H.-1 Periodic discharge measurements Oaily stage and discharge Figure 13. Type and duration of surface-water stage and discharge records and number of chemical analyses of surface water samples collected at gaging sites in and near Orange County. PAGE 51 WATER RESOURCES OF ORANGE COUNTY 39 TABLE 7. SITES WHERE MISCELLANEOUS SURFACE-WATER DATA HAVE BEEN COLLECTED. No. of chemical Station no. Station analyses 48 Bonnet Creek near Vineland 3 49 Christmas Creek near Christmas 1 50 Howell Creek near Maitland 2 51 Jim Branch near Narcoossee 2 52 Little Wekiva River near Forest City 1 53 Mills Creek near Chuluota 1 54 Reedy Creek near Vineland 2 55 Roberts Branch near Bithlo 56 Rock Springs near Apopka 7 57 Second Creek near Christmas 1 58 Settlement Creek near Christmas 59 Taylor Creek near Cocoa 1 60 Tootoosahatchee Creek near Christmas 61 Wekiva Springs near Apopka 5 62 Witherington Spring near Apopka 1 Table 8 gives the ranges in quality of surface water at selected sites in and near the county. Many of the data on surface water are presented as flowduration curves, stage-duration curves, flood-frequency curves, and low-flow frequency curves. Flow-duration curves (figures 14 and 15) are cumulative frequency curves that show the per cent of time specified discharges were equaled or exceeded during a given period. In a strict sense flow-duration curves apply only to the period in which the data used to develop the curve were obtained. Flow-duration curves are useful for predicting future flow distribution only if the data used represent the long-term distribution and if the climate and basin characteristics remain unaltered. Flow-duration curves based on less than 5 years of record were adjusted on the basis of concurrent records at a nearby site having a long-term record. The curves were thus made more representative of the longer periods. Flow-duration curves were estimated for the sites having only a few periodic observations by correlating these observations with concurrent data for nearby stations where data were complete. The shape of a flow-duration curve indicates the physical characteristics of the basin it represents. A curve that is steep PAGE 52 01 0 OJ O.2 O. I I 6 10 20 30 400 60 70 7 .-------S -J Slm Riverneor Chvistma (October 1934 to September 1962). S.St. John River near Cocoo (October 1953 to September 1962),. d. adjusted to (October 1934 to September 1962). Econckholtchdw River nar Chuluolo (October 1935 to Sepltembwer 1962). S y OreekRnear Taft (Octobd (O to Sptembertober 19 to Spb 1962. 50 Sdj-used ro (Oct 9tobr 9 5 to Septembe-r 1962 ) ---•-S. Songle Creek at airport netor Klmm9ee (Oc5ober1958 to September -1962) adjusted to(October1935 to September1962). -----6. Shingle Ecockhatch River near Union Prkiee (October 195 toSeptem-ber bet 196i)" adjusted Io(October 1935 to September 19621.-\0 ber 962) adjusted to(October 1935 to September 1962). -----------0 S .Cypress Creekat of Vinelond (October 1945 to September 1962) 20 30 40 50 60 70 80 90 95 S 8. 99 995 99.9890 99935 PERCENT OF TIME DISCHARGE EQUALED OR EXCEEDED THAT SHOWN __Fiure 14. Duration curves of daily flow for streams in and near PAGE 53 TABLE 8. RANGE IN QUALITY OF SURFACE WATER IN ORANGE COUNTY, FLORIDA (Chemical Analyses in parts per million, except specific conductance, PH, and color) Pero' Z o a 2; Dissolved solids Hardness as CaCO3 0 Period -3 S of "S a 0 | o Calcium NonX Source Record z X 0 o ' , Calculated Residue Magnesium| carbonate M jd Bo-gy Creek near Taft 11/59-7/63 21 0.8-10 .01-.33 3.8-8.8 0.7-4.3 5.5-14 0.8-2.8 934 1.2-6.4 9-18 0.1-0.7 0.0.9 29-73 59-134 1330 0-14 55-121 6.2-8.0 4-210 S1 Econiockharchee River nr. Bithlo 10/59-7/63 34 .08.9 .02-.50 2.6-26 .2-27 1.8-15 .2-1.5 883 .0-6.4 3.0-23 .0.8 .0-1.3 16-108 32-163 874 0-19 24-1971 5.7-7.8 35400 13 E-onlockhatchee River nr. Chuluota 5/53-7/58 36 1.7-12 .01-.60 3.6-51 1.0-14 .7-112 10-112 1.0-58 8.0-179 __ .0-14 32-468 _ 13-162 5-71 55-873 6.2-7.6 40-600 21 ar: Lake near Narcoossee 10/54-7/63 17 .54.1 .00-.31 1.7-8.8 .5-2.9 .9-11 313 .2-16 7.5-16 .0-1.4 20-52 _ 931 6-20 38-110 5.4-6.3 30-170 5 Johns Lake at Oakland 10/59-7/63 4 .01.6 .01-.18 7.2-8.0 2.9-6.1 10-20 6.0-8.0 713 26-42 18-24 .1.3 .0.4 77-111 114-146 3044 20-38 150-202 5.8-6.5 2580 3 Lake Apopka at Winter Garden 10/59-7/63 5 5.1-15 .01-27 28-38 8.8-13 8.4-23 3.3-13 104-186 15-20 16-25 .4.6 .9-3.7 149-229 206-285 106-150 0-25 333-385 7.0-7.9 2045 n Lake Mairland at Winter Park 10/59-7/63 5 .0.9 .00-.04 18-24 4.9-6.8 9.3-14 3.7-5.2 5772 24-31 15-20 .1.5 .0-2.8 104-131 128-154 6588 22-32 195-230 6.6-7.6 -10 26 Lir' e Elonlockhatchee River near Union Park 1/60-7/63 25 .3-11 .01-.66 5.4-16 .6-4.8 5.2-16 .2-2.4 951 1.2-6.8 9.5-20 .0.4 .0.8 35-75 69-146 1648 4-20 58-146 5.6-8.0 20-40 -Rock Springs near Apopka 4/56-7/63 7 8.2-10 .00-.35 27-30 7.1-9.7 3.9-5.1 .3.7 94-105 16-18 5.0-8.0 .0.3 .0-2.7 121-129 123-140 102-110 19-25 212-223 6.8-7.8 010 35 Sc. Johns River near Christmas 9/52-7/63 47 .2-11 .00-.43 7.5-162 2.2-77 11-621 21-138 2.0-364 20-1150 .0.5 .0-2.8 57-2350 -2830 28-720 11-672 110-4060 6.3-7.5 45-220 ;; St Johns River near Cocoa 10/53-9/63 170 .0-16 .00-.49 8.4-136 2.1-56 12-454 .0-14 21-136 2.5-156 21-900 .0.7 .0-5.3 67-1760 103-2320 30-570 9-494 107-3500 6.4-7.7 45-280 :: Shinrge Creek near Vineland 11/59-7/63 22 .08.8 .03-.73 2.8-21 .5-3.9 4.7-35 .0-5.1 562 .0-19 8.0-37 .1.5 .0-4.3 25-150 53-168 1266 0-19 48-268 5.7-7.8 45-200 W1 W-kiva Springs near Apopka 4/56-6/62 5 8.9-11 .00-.42 28-30 7.7-10 4.7-5.4 .4.8 103-123 6.0-12 7.0-8.5 .1.3 .0-2.7 123-134 131-139 104-114 11-24 215-240 7.3-7.6 05 PAGE 54 WATER RESOURCES OF ORANGE COUNTY 41 Oec © 5c 0o Os I b to o 30 e 4o 0 1,0I Wokive S pRgiver fi§ neatA=p= glow 8Aj@Y=Eot Tfeheren liga Conol e N meweese ,00 -=,l.. .. Wo @ Se == ngs ne= A=pop =oViel , to0 t00 o0 s P eROENT OB TIME eSHANGE =QUALED 0R EXOE= O THAT SHOWN .-----^^ __ __ ^ = ^ ^ ^^___ ^ __^ m sWkiva Spince nor roundwa, storae w h \ tends to equale 8R Rck SpfinoM nef APOO,\ 40 50 60 70 58 Ng 0§ N8 '?B§@8§^*ýM PERENT OF TIME DISCHARGE EQUALED OR EXCEEDED THAT SHOWN Figuro 1A5 Estimad fltra a tion urves for t tsloerm and springd s ot which periodic or i miscollaneous discharge data are available. throughout its range indicates a highly variable stream having little or no surface storage or ground-water storage. A curve with a flat slope throughout its range indicates the release of water from surfaceor ground-water storage which tends to equalize the flow. A curve that flattens out at its lower end indicates the release of ground-water storage at low flow. A curve that flattens at its upper end indicates release of storage from lakes or swamps at high flow. Flow-duration curves are useful for water power, water supply, and pollution studies. Stage-duration curves (figure 16) present stage data in the same way flow-duration curves present flow data. The limitations PAGE 55 42 REPORT OF INVESTIGATIONS NO. 50 'o02 -ILake Butler at Windermere (1941-63), S---;. 2 Johns Lake at Oakland (1959-63) adjusted to S(1941-63), 94 --3, Bass Lake near Orlando (1959-63) adjusted to 1(1941-63), 8 --4 Lake Corrine near Orlando(1943-49)(1959-63) --5,Lake Silver at Orlando(1959-63) adjusted to 11 _ __ ' (1941-63), 4G 6 Lake Conway at Pine Castle (1952-63). Ss _ _ 7 Lake Apopka at Winter Gorden (1942-63). 62 S_8 Lake Moitland at Winter Pork(1945-52)(1959-63) S9Lake Francis near Plymouth (1959-63) adjusted 4 ...to (1941-63), 10 Lake Dora at Mount Dora (1942-63). I ,Lake Mary Jone nar Norcoossee (1949-63), S0 -12,Lake Hart near Norcoossee (1941-63), '. f „ -13.Lake Poinsett near Cocoa (1941-63), 2 --14,Lake Cone near Christmas (1933-63) records for 0 St. Johns River near Christmoas, 0 o1 20 30 40 0O 60 70 0 90 100 PuRCENT OF TIME ALTITUDCE UALeD OR EXCLDEOD THAT SHOWN Figure 16. Stage-duration curves for selected lakes. PAGE 56 WATER RESOURCES OF ORANGE COUNTY 43 in the use of flow-duration curves for predicting future flows are applicable to the prediction of future stages by use of stageduration curves based on short records can be adjusted to longer periods by correlation with records for a long-term station. This has been done for the stage stations established for this investigation. Knowledge of the magnitude and probable frequency of floods is essential to the proper design and location of water-related structures such as dams, bridges, culverts, levees, etc., and any other structures that may be located in areas subject to periodic flooding. Such knowledge is also useful in solving problems associated with flood insurance and flood zoning. Because flood-frequency information is often needed for locations where no flow data are available, methods have been devised that permit determination of the probable magnitude and frequency of floods at any point along a stream. Methods of determining the probable magnitude and frequency of floods of recurrence intervals from 1.1 to 50 years on streams in Orange County are given in U. S. Geological Survey Water-Supply Paper 1674 (Barnes and Golden, 1966). Because of the importance of stage in floods on the main stem of the St. Johns River, stage-frequency data are presented in the form of water-surface profiles for floods of recurrence intervals of 2.33, 5, 10 and 30 years (figure 17). These profiles are for the reach between the southern Orange County line and State Highway 46. A low-flow frequency curve shows the average interval between the recurrence of annual low flows less than the indicated values. Curves for durations of 7, 30, 60, 120, and 183 days, 9 months, and 1 year are given. These curves are useful in determining whether the natural flow of a stream is adequate for a particular development and, if not, how much the natural flow must be augmented from storage or some other source. In Orange County only the St. Johns River, the Econlockhatchee River, and the Wekiva River has sufficient low flow to warrant analysis. SURFACE DRAINAGE Surface water from the southwestern 341 square miles of Orange County drains southward into the Kissimmee River. Surface water from the eastern and northern 662 square miles of the county drains northward into the St. Johns River. Figure 18 PAGE 57 179^^-----1--------------------------r·----------------r--------------j(0 S I-^-----? --? 14J _ _ " i 12 0, O5 10 15 '20 25 30 35, 'DISTANCE IN MILES ALONG MAIN STEM OF ST. JOHNS RIVER Figure 17. Water-surface profiles for floods of selected recurrence intervals .__...__________.____. .on main stem of St. Jo1---River in Orange County. PAGE 58 Q i 5'5 40' 35' 30' 25' 20' 15' 10' 05' i 81000' 55' 80050' -I 1 , L .I I [ I I , I I I I I I I I III II I I 1 1 I I 1 1 1 1 1 1 1 1 1 1 1 28 5o0 ' .., MOU T 46 :DORA 4 c" 6ORANGE COUNTY SLAK E COUNTY EXPLANATION N \ ORANGE COUNTY -Major Drainage Divide .----Tributary Drainage Divide S56 U .......... High-water Line from Profile Gages ) -5' \ -3 Cities and Towns -62--, Surface Water Data Collection Point A " Quality-of-water Data Collection Point, Surface Source 11 _ e ,---A 611r "% 7 J" \19 Station Number Refers to Figure 13 and Table 7,8,11 and 12 LLYMOUiH P rI AP OPKA 7 , .--n/oc ho. r., ._ _N f, . ..FOREST, 52 A5' zi _ j B CITY .0 4IMIN 0 LE creee HULUOT 70R NGE E lowe iOR Y~__0)I 43 ' ~ ~ 53 NT C U T OU TYU T PAR # O" .. S ) V 35' 5 42 2 4 UNIO '~B ' -.... / .. ' -5 :14 PARKo 50 4-Z5 ,' ,·.. " ,.. y 3 "2 r-O.....0 PHI.v 47P25 4 O 4 no0' ' 2 50 S 1 2 3 4 5 6 7 8 9 0 miles Fiue18ri b s s arc 4 u 18.'ECAS D n bfl A PH 4Pgk-\ TAF YY ;1 I Or 5 15 1 -ZI ro Y ........ 0 U 4 T Y K dli/ 20 'EM.136 1 0 2 5 4 5 9 10 ile Fiue1.Driaebsnsadsrae-ae olcto ons PAGE 59 WATER RESOURCES OF ORANGE COUNTY 45 shows the drainage basins and the surface-water data-collection points in Orange County. Parts of some of the basins delineated on figure 18 are closed basins that do not contribute direct surface runoff. The efficiency of a stream in removing surface water from the land is closely related to the average slope of its bed. During the flood of March 1960, rainfall on Jim Creek basin above State Highway 520 (drainage area 22.7 sq mi) and on Boggy Creek basin above the station near Taft (drainage area 83.6 sq mi) was about the same. Even though the contributing area of Boggy Creek is more than three times that of Jim Creek, its peak flow was only 3,680 cfs whereas that of Jim Creek was 3.750 cfs. This anomaly can be explained in part by the reduction of the peak flow on Boggy Creek by storage in lakes and swamps. It is due mostly, however, to the fact that the slope of Boggy Creek (3 feet per mile) is about half that of Jim Creek. Streambed profiles for most of the streams in Orange County are included in this report. KISSIMMEE RIVER BASIN Reedy Creek Reedy Creek drains 49 square miles in the southwest corner of Orange County. The drainage from about 22 square miles of this basin in Lake County flows into Orange County. The drainage area above the gaging station near Vineland (station 54) is 75 square miles. Land surface altitude in Reedy Creek basin in Orange County ranges from 75 feet above msl at the southern county line to 210 feet at Avalon fire lookout tower. The eastern part of the basin consists of relatively flat swampy terrain interspersed with islands of low relief. The western part consists of rolling hills interspersed with lakes and swamps. The divide between Reedy Creek basin and Bonnet Creek basin to the east is rather indefinite, and there is some interchange of water between basins. Figure 19 shows a profile of the bed of Reedy Creek. At Reedy Creek near Vineland (station 54, 1 mile south of the county line, the minimum flow observed was less than 0.01 cfs in May 1961. The maximum flow was 1,910 cfs at the peak of the flood in September 1960. The average flow of Reedy Creek near Vineland is estimated to be 55 cfs or 0.73 cfs per square mile. Average yearly runoff from PAGE 60 le WM ?( cc 0 a to 5 4 w z -, 9 jy § -go x-O----____ -___ § DISTANCE FROM COUNTY LINE,IN MS r----I-~ 07 PAGE 66 52 REPORT OF INVESTIGATIONS NO. 50 Jim Branch Jim Branch drains 5.8 square miles in the south-central part of Orange County. Altitudes in the basin range from 75 to 85 feet. Figure 20 shows a profile of the bed of Jim Branch. The maximum flow of Jim Branch near Narcoossee (station 51) has not been determined. A dry stream channel has been observed at station 51. Water collected from Jim Branch on May 23, 1961, was very soft (9 ppm) and low in mineral content (30 ppm, estimated from its conductivity). Ajay-East Tohopekaliga Canal This canal drains approximately 171 square miles, of which 54.5 square miles are in Orange County and 116.5 square miles are in Osceola County. Altitudes of the drainage area in Orange County range from 60 to 90 feet. The topography is fairly flat and is characterized by swamps in the northern part and by lakes in the southern part. Periodic measurements of the flow in Ajay-East Tohopekaliga Canal near Narcoossee (station 2) have been made since 1942. The maximum measured discharge was 1,420 cfs in March 1960. A reverse flow of 0.25 cfs was measured in February 1946. The average discharge, based on the relation between drainage area and average discharge at several points on the main stem of the Kissimmee River, is estimated to be about 170 cfs or 1.0 cfs per square mile. The flow into Orange County from an area of 111 square miles in Osceola County has been measured in Myrtle-Mary Jane Canal near Narcoossee (station 31) since November 1949. The maximum flow into the county via this canal was 990 cfs in September 1960. In September 1956, the flow reversed for 2 days and flowed out of the county at the rate of 17 cfs. The average discharge in this canal for the period of 1950 to 1963 was 109 cfs or 0.98 cfs per square miles. Average annual runoff is 13.6 inches at station 2 and 13.3 inches at station 31. This indicates fairly uniform yield from all parts of the basin. Curve 2 (figure 15) is the estimated flow-duration curve for station 2 and figure 21 is the flow-duration curve for station 31. The flatness of the upper parts of these curves indicates the large amount of storage in the lakes and swamps in this basin. PAGE 67 WATER RESOURCES OF ORANGE COUNTY 53 1,000 700 Period of record' "500 ---October 1950 to September 1962 300 ------^ !t ---------2 00 0 :_ FLOW TO NORTH __ 50 NOTE.--No flow 2,87 prcent of time D 07 --FLO TO SOUTH 0.5 0.3 PERCENT OF TIME DISCHARGE EQUALED OR EXCEEDED THAT SHOWN Figure 21. Flow-duration curve for Myrtle-Mary Jane Canal near Narcoossee. Water from Ajay-East Tohopekaliga Canal, collected at station 2 during low flow on May 23, 1961, was very soft (16 ppm), and low in mineral content (39 ppm, estimated from its conductivity). ST. JOHNS RIVER BASIN St. Johns River The St. Johns River is the eastern boundary of Orange County. Small tributaries drain 174 square miles of Orange County directly to the St. Johns River. An additional 490 square miles of the county are drained to the St. Johns River by tributaries which flow across the county line from the south before joining the main stem. PAGE 68 54 REPORT OF INVESTIGATIONS No. 50 The average slope of the St. Johns River is less than 0.3 of a foot per mile in its approximately 26-mile reach along the border of Orange County. At flood stages, the river falls from an altitude of about 17.5 feet at Lake Poinsett to about 10.5 feet at the northern county line. At the minimum stages in 1945, the river fell from 8.0 feet to minus 0.4 foot in this reach. Figure 17 shows probable flood altitudes for the St. Johns River for selected recurrence intervals. Stage and discharge records have been collected at St. Johns River near Christmas (station 35) since December 1933 and at St. Johns River near Cocoa (station 36) since October 1953. The average discharge for the period of record at station 35 was 1,379 cfs. For the 10-year period October 1953 to September 1963, the average discharge at station 35 was 1,463 cfs; and at station 36, 1.237 cfs. The maximum flow during the period of record at station 35 was 11,700 cfs in October 1953. There was no flow at station 35 for periods during March, April, and June 1939. Average yearly runoff is 13.2 inches at station 35 and 12.8 inches at station 36. The slightly higher yield at station 35 may be due partly to the absence of lakes, where evaporation losses are high, and partly to upward seepage of artesian water in the area between the two stations. Curves 1 and 2 (fig. 14) are flow-duration curves for stations 35 and 36. As indicated by the curve, about 99 percent of the time flow at station 35 exceeds that at station 36 but 1 percent of the time evaporation and transpiration demands on the river exceed the seepage into the river causing a loss in flow between the stations. Figure 22 shows the magnitude and frequency of annual minimum flow for selected durations at station 35. Analyses of water collected daily from the St. Johns River near Cocoa (station 36) from October 1953 to September 1960, and a continuous record of its conductivity since June 1959 show that the quality of the water varies greatly. Table 8 gives ranges for the various dissolved constituents. Except for color the quality of the water in the St. Johns River near Cocoa is good during normal and high flows. During droughts when low flows occur, the water in the St. Johns River becomes highly mineralized. During extended droughts, as occurred in 1962, very little water flows into the St. Johns River above the Wekiva River. Most of the low flow comes from seepage of highly mineralized artesian water from the Floridan aquifer. Along the reach of the river adjacent to Brevard County, the Floridan aquifer PAGE 69 WATER RESOURCES OF ORANGE COUNTY 55 3000 2000 Drainage area: 1418 sq. mi. Average flow: 1379 cfs o 1000 Fr-y Zo 00 wi thr is con \si de rabe lea e Ia t ,e r n u 200 ---^ ^ ^ -^ --500 n man flow is 41t c 5 of aIUS 1.2 1.5 2 3 4 5 7 000 15 20 -0 5 50 ------k -s --^ -^ .LOW-FLOW FREQUENCY RECURRENCE INTERVAL IN YEARS Figure 22. Low-flow frequencies for St. Johns River near Christmas. is overlain by a thin aquiclude (impervious formation) through which there is considerable leakage. In addition, there are many wells heavily pumped for irrigation, and the excess water flows through drainage ditches to the St. Johns River. Many artesian extended droughts the mineral content of the water in the St. Johns River above the Wekiva River approaches that of the highly mineralized artesian water. The water in the St. Johns River was very highly mineralized during the drought in the spring and early summer of 1962. Figure 23 shows a chloride profile of the river from headwaters to Green Cove Springs from May 29 to October 24, 1962. This extended reach of the river is shown for comparative purposes. Figure 23 PAGE 70 56 REPORT OF INVESTIGATIONS No. 50 S-" .-River 11000 Oft{LI{K 9 1600 0 AN E I .0 I WI.W 1 04 Figure 23. Chloride concentration in St Johns River, northeastern Florida. shows that the quality of the water in the St. Johns River is highly variable, especially from the headwaters to State Highway 46 and in the lower reaches where salt-water encroachment occurs. At low flow the most abundant constituent in the water is chloride, but sodium, sulfate, calcium, and magnesium are also present in high concentrations. Table 9 presents a comparison of the chemical 1Nx1 1 ~2000 analyses of water in the St. Johns River on June 7, 1962 at State Highways 520 (station 36), 50 (station 35), and 16. The increase in concentration from State Highway 520 to State Highway 50 was caused by more ground-water inflow. The high concentrations of dissolved minerals at 'State Highway 16 are caused by sea-water encroachment. The lower concentrations at low flow between the Wekiva River and U. S. Highway 17 are caused by dilution from relatively fresh spring flow. As the rainy season began in late June 1962, the flow in the St. Johns River increased and the quality of the water improved. hish concentrations. Table 9 presents a comparison of the chemical concentrtions of dissolved minerals at'State Highway 16 are low flow between the Wekiva River and U. S. Highway 17 are caused by dilution from relatively fresh spring fow. As the rainy season began in late June 1962, the flow in the St. Johns River increased and the quality of the water improved.,, PAGE 71 WATER RESOURCES OF ORANGE COUNTY 57 TABLE 9. CHEMICAL ANALYSES OF ST. JOHNS RIVER WATER, JUNE 7, 1962. Analysis State Highway State Highway State Highway (ppm) 520 50 16 Chloride 900 1,150 2,050 Sodium 454 606 1,270 Sulfate 150 248 315 Calcium 136 160 196 Magnesium 56 77 79 Hardness 570 716 814 As indicated by figure 23, the quality of the water in the headwaters improves early with increased flow, but remains poor downstream until the highly mineralized water stored in the lakes is flushed out. The chloride concentrations in the water on October 24, 1962 indicate that most of the highly mineralized water was flushed from the river. Figure 24 shows a cumulative frequency curve of specific conductance of the water-the percent of time the specific 400 S200-a 60 Z 40--S20 05 1 2 5 10 20 3040 50 60 70 80 90 95 98 99 995 999 99.99 PERCENT OF TIME SPECIFIC CONDUCTANCE WAS EQUALED OR EXCEEDED Figure 24. Cumulative frequency curve for specific conductance of the St. Johns River near Cocoa, October 1953 -September 1963. PAGE 72 58 REPORT OF INVESTIGATIONS NO. 50 conductance equals or exceeds values shown-in the St. Johns River near Cocoa from October 1953 to September 1963. For example, the conductance was 3,000 or greater for 2 percent of the time during the period of record. Figure 25 shows the relation of specific conductance to sodium, hardness, chloride and mineral content in water of the St. Johns River near Cocoa. By using figure 24 in conjunction with figure 25 the percentage of time that the various constituents would exceed a given value can be estimated. For example, from figure 25, if the chloride content was 250 ppm, the specific conductance would be about 1,020 micromhos. From figure 24 a conductance of 1,020 micromhos or greater would occur about 18 percent of the time. From October 1953 to September 1963, the mineral content and chloride concentration in water in the St. Johns River near Cocoa exceeded the U. S. Public Health Standards for drinking water during the following periods: April 21 to September 10, 1956; June 21 to July 31, 1961; October 13, 1961 to August 21, 1962; 4,000 V/ SHARDNESS 3,000-SODIUM MINERAL CONTENTCHLORIDE X '/ /o I 200 400 600 800 1000 1200 ,1,400 1,600 21000 2.000-PARTS PER MILLION Figure 25. Relation of specific conductance to hardness, chloride, sodium, and mineral content for St. Johns River near Cocoa. S UQ ----^-------^/------------zjI / /> mineral content for St. Johns River near Cocoa. PAGE 73 WATER RESOURCES OF ORANGE COUNTY 59 and June 20 to July 31, 1963. This would be about 15 percent of the time in the 10-year period of record. A spectrograph analysis for minor elements was made on water collected from the St. Johns River near Cocoa at low flow on May 11, 1962. The results in micrograms per liter are given in Table 10. Micrograms per liter can be converted to ppm by dividing by 1,000. The symbol > indicates that the concentrations are less than the values shown which are the lower limits of detection. Small Tributaries Draining To East The eastern part of the county between the main stem of the St. Johns River and the Econlockhatchee River, amounting to about 180 square miles drains to the St. Johns River by numerous small tributaries. Table 7 shows data pertinent to these tributaries. Figure 26 shows profiles of the beds of several of the small tributaries. The hydrologic characteristics of all these small streams are probably similar to those of Jim Creek. Curve 3 (fig. 15) is the estimated flow-duration curve for Jim Creek near Christmas (station 24). The relative straightness of this curve indicates the small amount of storage both on the surface and in the ground in this area. Its steepness is indicative of the extreme variability associated with steep bed slope and absence of storage. As indicated by the curve, streams in this area are dry about 20 percent of the time. The average flow at station 24 is estimated to be 26 cfs or TABLE 10. MINOR ELEMENTS IN WATER FROM ST. JOHNS RIVER NEAR COCOA ON MAY 11, 1962. (Quantitative results in micrograms per liter. The symbol < indicates concentrations are less than the values shown which are the lower limits of detection) Aluminum 66 Germanium < 0.29 Beryllium < 0.57 Manganese < 1.4 Bismuth < 0.29 Molybdenum < 1.4 Cadmium < 1.4 Nickel 1.9 Cobalt < 1.4 Lead < 1.4 Chromium < 1.4 Titanium < 5.7 Copper < 1.4 Vanadium 0.54 Iron 5.1 Zinc < 5.7 Gallium < 5.7 PAGE 74 0 so o I I -.. -A COUNTY LINE ---B EDGE OF ST JOHNS RIVER FLOOD PLAIN C STATE HIGHWAY 50 _______ 0 STATE HIGHWAY 420 E STATE HIGHWAY 520 , S F TAYLOR CREEK ROAD / 50 w I-I If" -' e' "E-I i "0 ' I x .. 0 10 NOTE: Data taken from U. S.G.S. Topograohi o aBc M 0 I 2 3 4 5 6 7 8 9 10 II 12 13 14 I S I 16 I1 s DISTANCE FROM ST. JOHNS RIVER, IN MILES Figure 26. Streambed profiles of small streams draining east into St. Johns River. PAGE 75 WATER RESOURCES OF ORANGE COUNTY 61 1.15 cfs per square mile. Average runoff from the area is estimated at 15.6 inches. During the low flow period from June 14 to 17, 1960, the dissolved mineral content in the water in the small tributaries draining eastward into the St. Johns River was estimated from conductivity measurements to range from 33 ppm in Taylor Creek to 86 ppm in Second Creek. The mineral content in the water in Christmas Creek was estimated on basis of its conductivity, to be 52 ppm on May 24, 1961, when the other small tributaries were dry. Lake Pickett Lake Pickett and its contributary drainage area occupy 8.1 square miles. Mills Creek drains Lake Pickett to the Econlockhatchee River. Altitudes in the Lake Pickett drainage basin range from 60 to 75 feet. The hardness of the water in Mills Creek at Chuluota (station 53) on May 24, 1961, was 7 ppm and the mineral content, estimated from its conductivity, was 21 ppm. The pH of the water was 5.9 indicating that it is slightly corrosive. The water quality of Lake Pickett is similar to that of Mills Creek. Econlockhatchee River The Econlockhatchee River drains 117 square miles of Orange County. The width of drainage basin ranges from 2.5 to 9.5 miles with the average in Orange County being 6.2 miles. The basin is about 14 miles east of Orlando and spans the county from south to north. The drainage from 17 square miles of the basin in Osceola County enters Orange County. Altitudes in the Econlockhatchee River basin in Orange County range from 20 to 90 feet. Figure 27 shows profiles of the beds of Econlockhatchee River and several of its tributaries. The Econlockhatchee River basin and the area drained by small tributaries to the St. Johns River are unusual for Orange County in that they contain only three lakes of significant size. These basins do, however, contain many swamps and marshes. Continuous records of the flow of the Econlockhatchee River near Chuluota (station 19) have been collected since 1936, and periodic measurements of the flow of the Econlockhatchee River near Bithlo (station 18) have been made since September 1959. The maximum flow of record at station 19 was 11,000 cfs and at PAGE 76 E j l h , ! _ _ ,r --er S i El i-hI9C -t ----I-^----I 0 41w0 --~ L I ~ -9 0 * I 0 I 2 3 4 s 6 7 8 9 10 11 12 13 M4 16 7 18 19 20 21 22 23 24 25 26 27 28 DISTANCE FROM COUNTY LINE, IN MILES Ot 0 Figure 27. Streambed profiles of Econlockhatchee River and selected tributaries. PAGE 77 WATER RESOURCES OF ORANGE COUNTY 63 station 18, it was 7,840 cfs, both in March 1960. The minimum flow at station 19 was 6.7 cfs in June 1945. The river flow ceases at station 18 in most dry years. The average flow at station 19 was 275 cfs or 1.06 cfs per square mile for the period 1936 to 1963. The estimated average flow at station 18 is 88 cfs or 0.74 cfs per square mile. Runoff from the part of the basin above this station is estimated to be 10 inches per year. Average runoff from the entire basin above station 19 is 14.4 inches per year. Runoff from the area above station 26 on Little Econlockhatchee River is estimated to be 10 inches per year. Prorating the 10 inches of runoff from the 146 square miles above stations 18 and 26 with the 14.4 inches from the 260 square miles above station 19 gives an average yearly runoff from the intervening 114 square miles of 20 inches. About 11/ inches (11 cfs) of the 10-inch increase in runoff from the lower basin over runoff from the upper basin is accounted for by the effluent from Orlando's sewage plant. The remaining 8.5 inches is accounted for by higher base flow resulting from ground-water seepage into the more deeply incised channel in the lower basin and possibly upward seepage of artesian water. Curve 3 (fig. 14) is the flow-duration curve for station 19 and curve 1 (fig. 15) is the estimated flow-duration curve for station 18. Note the similarity in the shape of the curves up to 50 percent duration when direct runoff is the main source of flow. Above 50 percent the curve for station 18 falls off rapidly to no flow at 75 percent reflecting the absence of base flow whereas the curve for station 19 continues on at about the same slope reflecting the base flow supplied by the sewage effluent and ground-water seepage. Low-flow characteristics of Econlockhatchee River at station 19 are shown by figure 28. The streamflow indicated by these curves is somewhat more than occurs within Orange County. A continuous record of conductivity from October 1959 to June 1962 and analyses of water collected periodically to July 1963 from the Econlockhatchee River near Bithlo (station 18), show the water to be high in color, soft, and low in mineral content. Table 8 gives the ranges of mineral constituents from October 1959 to July 1963. The color is always greatest during the early part of high-flow periods. The pH of the water was as low as 5.7 during high-flow periods which indicates that the water would be slightly corrosive. The high percentage of calcium bicarbonate detected during low-flow periods indicates that ground-water inflow may occur. Figure 29 shows a cumulative frequency curve of specific conductance of the water in the Econlockhatchee River near Bithlo PAGE 78 64 REPORT OF INVESTIGATIONS NO. 50 1000 -LOW-FLOW FREOUENCY 700 Example: For a 10-year recurrence interval the 7-day minimum flow _ is 12.5 cfs and the I-year minimum 500 ---flow is 112 cfs 300 z 200 Z 50 ---0 Uj a-a area 260 sq mi. Average flow: 277 cfs 10 ---rn are 2 sq m. ---1.01 1.05 I.I 1.2 1.5 2 3 4 5 7 10 15 20 30 RECURRENCE INTERVAL, IN YEARS Figure 28. Low-flow frequencies for Econlockhatchee River near Chuluota. PAGE 79 WATER RESOURCES OF ORANGE COUNTY 65 6,000 m ~ ~~~~~~~~~~~ -------------------t 4,000 ,j =,000 600 05 2 5 I0 20 30 40 50 60 70 80 90 95 98 99 995 999 9999 PERCENT OF TIME SPECIFIC CONDUCTANCE WAS EQUALED OR EXCEEDED Figure 29. Cumulative frequency curve of specific conductance of the Econlockhatchee River near Bithlo, October, 1959 -May, 1962. from October 1959 to May 1962. Figure 30 shows the relation of specific conductance to hardness and mineral content for the Econlockhatchee River near Bithlo. Hardness and mineral content were the only properties of the water that could be related to the specific conductance for the Econlockhatchee River. The sodium, z z chloride, and sulfate content is usually very low. By using figure 29 in conjunction with figure 30, the percentage of time that hardness and mineral content would exceed a given value can be estimated. Little Econlockhatchee River The Little Econlockhatchee River drains 71 square miles of Orange County east of Orlando. Altitudes in this basin range from about 3nc feet near the countye percento 127 feet at the eastern edge of Orlando n Figure 27 shows a profile of the bed of the Little Econlockhatchee River. A few lakes exist along the western rim of the basin but none exist elsewhere. Many swamps and marshes temporarily store water and thereby reduce the magnitude of peak flows in the river. PAGE 80 66 REPORT OF INVESTIGATIONS NO. 50 220 HARDNESS I MINERAL CONTENT Figure 30. Relation of specific conductance to hardness and mineral content 5 " ° -----~ ------of this curve indicate a highly variable stream in a basin having ~I c _ _---------_-------40 0 t0 20 30 40 O50 60 70 80 90 100 110 PARTS PER MILLION Figure 30. Relation of specific conductance to hardness and mineral content for Econlockhatchee River near Bithlo. The flow from the upper 27 square miles of the basin has been gaged since October 1959 at Little Econlockhatchee River near Union Park (station 26). The maximum and minimum flows at this station were 1,640 cfs in March 1960 and 0.1 cfs in June 1961. The average flow of the period October 1959 to September 1963 was 24.5 cfs. The long-term average is estimated to be 20 cfs or 0.74 cfs per square mile. Average runoff from the area above station 26 is estimated at 10 inches per year. Curve 7 (figure 14) is the flow-duration curve for station 26. The steepness and straightness of this curve indicate a highly variable stream in a basin having little surface or ground-water storage. Analyses of water collected from the Little Econlockhatchee River at station 26 show that the quality is similar to that of the Econlockhatchee River. Table 8 gives ranges of concentrations and properties of water in Little Econlockhatchee River. PAGE 81 WATER RESOURCES OF ORANGE COUNTY 67 Howell Creek Howell Creek drains about 20 square miles in Orange County, mostly in the suburban areas of Maitland, Winter Park, and the northern half of Orlando. Altitudes in the Howell Creek basin range from about 55 to 125 feet. This basin contains a chain of lakes connected by natural channels, canals, and culverts, beginning at Spring Lake at Orlando (station 42), at an altitude of about 88 feet and ending at Lake Maitland at Winter Park (station 28), at an altitude of about 66 feet. Several other lakes are connected to the chain of lakes by canals or culverts. Lake Underhill at Orlando (station 45), in the Boggy Creek basin, is connected to Lake Highland in the Howell Creek basin by a culvert. The flow of Howell Creek near Maitland (station 50) has been measured several times. The maximum discharge of record as determined from the stage-discharge relation was about 160 cfs in September 1960. Flow at this site ceases when the level of Lake Maitland is below about 65.5 feet with the center board of the control out or about 66.0 feet with the center board in. The levels of many of the lakes in the basin are partly controlled by drainage wells and the flow from the basin is accordingly modified. The average flow at station 50 is estimated to be 40 cfs or 2 cfs per square mile. Runoff is estimated to average about 27 inches per year; more than half of the average annual rainfall. This yield is much greater than elsewhere in the county despite the high percentage of area covered by lakes from which the loss by evaporation probably approaches the total rainfall on the lakes and water discharged to the aquifer through drainage wells. This high yield is due to the large percentage of area covered with pavement and roofs from which runoff is a high percentage of rainfall. Figure 31 shows estimated flow-duration curves for station 50. The percentages indicated are for the time the control was in one or the other of the conditions indicated and not for the total period of record. A record of board changes is not available, so a consolidated flow-duration curve cannot be prepared. The water in Howell Creek and Lake Maitland are similar and are of good quality except for moderate hardness which indicates ground-water inflow. Hardness at high and low lake levels was 65 and 88 ppm, respectively. Table 8 gives ranges for other dissolved constituents and properties of the water in Lake Maitland. PAGE 82 68 REPORT OF INVESTIGATIONS No. 50 160 140 0 z 0 400 Li\ F OR PART OF TOTAL TTIME WHEN CENTERBOARD z WAS NOT IN PLACE 20 U; A z FOR PART OF TOTAL TIME WHEN CENTERBOARD 20 WAS IN PLACE >-)0 -----I-------I---oOI 005 I 02 o5 2 5 10 20 30 40 50 60 70 80 90 95 PERCENT OF TIME DISCHARGE EQUALED OR EXCEEDED THAT SHOWN Figure 31. Estimated flow-duration curves for Howell Creek near Maitland. Wekiva River The Wekiva River and its tributaries, the Little Wekiva River and Rock Springs Run, drain about 130 square miles in Orange County. Altitudes in this basin range from about 15 feet at the northern county line to about 195 feet near Windermere. Figure 32 shows profiles along the beds of streams in the Wekiva basin. The area near the stream channels is flat and swampy, and ranges in altitude from about 15 to 30 feet. From the edges of these flat swamps, rolling hills rise abruptly to altitudes ranging between 60 and 100 feet. More than half of the Wekiva River basin in Orange County consists of rolling hills interspersed with lakes and sinks. There is no surface outflow from this area. Records of the daily stage and discharge of the Wekiva River near Sanford (station 46) have been collected since October 1935. The topographic drainage area at this station is about 200 square miles. The average discharge for the period 1935-63 was 276 cfs. PAGE 83 WATER RESOURCES OF ORANGE COUNTY 69 ALTITUDE,IN FEET ABOVE MEAN SEA LEVEL ' COUNTY LINE N -Witherint' on Spring STATE HIGHWAY 436 0 \. PREVATT LAKE a \ \ ---LAKE CORONI SSTATE HIGHWAY 43 -0 -LAKE McCOY r S-STATE HIGHWAY 435 RIVERSIDE ACRES B" U.S. HIGHWAY 441m _ -U.S. HIGHWAY 441 LAKE WEKIVA -LAWNE LAKE -5 -STATE HIGHWAY 50 Figure 82. Streambed profiles for Wekiva River and tributaries. The maximum discharge was 2,060 efs in September 1945 and the minimum, 105 efs in June 1939. Curve 4 (figure 14) is a flow-duration curve for station 46. The flatness of this curve indicates the small amount of surface inflow in relation to the very hih base flow of this stream. The -I N --I -----I --\ -----I -----inflow in relation to the very high base flow of this stream. The PAGE 84 70 REPORT OF INVESTIGATIONS NO. 50 average flow at this station is the same as that at Econlockhatchee River near Chuluota (station 19), yet the peak flow is less than one-fifth that at station 19 and the minimum flow about 16 times that at station 19. At station 46, the maximum flow is only 20 times as great as the minimum flow while at station 19, the maximum flow exceeds the minimum flow by more than 1,600 times. This great difference in variability is due to the fact that about one-third of the rain that falls on Wekiva River basin and nearby areas seeps downward into the artesian aquifer where it is stored until released slowly through many springs whereas little of the rain that falls on Econlockhatchee seeps into the artesian aquifer but instead remains on or near the surface from where about one-fourth of it runs off very rapidly. Figure 33 gives low-flow frequency curves for Wekiva River. 500 .--.-.[--.. 365 days Average flow: 275 cfs /273 days 400 183 days S//120 days LOW-FLOW FREQUENCY SK y 60 days Example: For a 10-year recurrence SI 30 days interval the I-day minimum flow is CL I / 139 cfs and the 365-days minimum 300 --flow is 221 cfs ___ S00-15 dayso --7 days I day 1.01 1.1 1.2 1.5 2 3 4 5 7 10 20 30 Recurrence interval in years Figure 33. Low-flow frequencies for Wekiva River near Sanford. PAGE 85 WATER RESOURCES OF ORANGE COUNTY 71 The flow of Rock Springs, Wekiva Springs, and Witherington Spring (stations 56, 61, and 62) near Apopka in the Wekiva River basin have been measured occasionally since 1931. Table 11 shows the results of these measurements. The average flow from Wekiva Springs is estimated to be 74 cfs and from Rock Springs, 60 cfs. Curves 7 and 8 (figure 15) show flow-duration for Wekiva Springs and Rock Springs, respectively. The extremely flat slope of these curves is due to the small variation in flow characteristic of ground-water sources. The quality of water from Rock and Wekiva Springs is similar to that of the ground water in the area, and it varies only slightly with flow. Table 8 gives ranges of dissolved constituents and properties of the water in Rock and Wekiva Springs. Apopka-Beauclair Canal This canal drains Lake Apopka and the surrounding areas. The total area drained by the canal is about 180 square miles, of which about 120 square miles is in Orange County. Altitudes in this basin range from about 65 feet in the mucklands adjacent to Lake Apopka to 225 feet near Lake Avalon. The flow in Apopka-Beauclair canal near Astatula was measured periodically at station 3 from 1942 to 1948. Since July 1958 the daily flow has been determined at station 4. During the period of record, the maximum flow at station 4 was 754 cfs in March 1960 and the minimum flow was estimated to be about 1 cfs during periods when a control structure in the canal was closed. The average flow at station 4 during the period 1958-63 was 118 cfs. Flow-duration curves and flow-frequency curves have no significance at this station because of the artificial regulation of the flow; therefore none are given. The quality of the water in Apopka-Beauclair canal is similar to that in Lake Apopka. The water quality of Lake Apopka is discussed under the following section on lakes, swamps, and marshes: LAKES OCCURRENCE Orange County has about 1,100 permanent bodies of open water ranging from small water-filled sinks to widenings of stream PAGE 86 TABLE 11. DISCHARGE MEASUREMENTS OF SPRINGS IN ORANGE COUNTY, FLORIDA. Downstream location Discharge of measuring section Name of spring and Date of in relation to head station number measurement (cfs) (mgd) of spring (feet) Rock Springs (56) 25-31 55.9 36.1 50 38-32 51.9 33.5 50 2-10-33 54.2 35.0 40 1-30-35 62.8 40.6 80 117-35 57.1 36.9 50 126-35 62.8 40.6 500 14-36 54.9 35.5 600 14-36 56.2 36.3 60 67-45 52.5 33.9 50 59-46 59.1 38.2 30 4-26-56 54.7 35.4 1,000 11-24-59 70.0 45.2 150 11-24-59 72.4 46.8 1,200 6-17-60 78.2 50.5 1,250 z 10-17-60 83.2 53.8 1,250 5-25-61 68.4 44.2 1,300 Wekiva Springs (61) 38-32 63.9 41.3 100 2-10-33 66.9 43.2 100 117-35 72.5 46.9 300 67-45 64.8 41.9 200 59-46 67.5 43.6 150 4-27-56 62.0 40.1 200 PAGE 87 TABLE 11. CONTINUED 11-25-59 88.8 57.4 300 6-17-60 86.0 55.6 200 10-17-60 91.7 59.3 150 5-25-61 86.6 56.0 150 Witherington Spring (62) 88-45 4.69 3.03 4,200 10-19-60 12.0 7.76 4,750 o '.4 PAGE 88 74 REPORT OF INVESTIGATIONS NO. 50 channels. Lakes occur in all parts of the county, but the vast majority of them are in the western half. SURFACE AREAS The surface areas of lakes in Orange County range from less than one acre for some sinkhole lakes to 31,000 acres for Lake Apopka. The area of a lake continually changes. If the range in stage of a lake is large and its shores slope gently, changes in its area are large. If the range in stage is small or if the shore is steep, changes in area are small. DEPTHS The shallowest of the permanent lakes in Orange County is Lake Poinsett. This lake was only 2-feet deep when it was at its lowest level in 1945. The deepest body of water in the county is Emerald Spring, a sinkhole near Little Lake Fairview. Emerald Spring was sounded to a depth of 334 feet. Depth contours for 73 selected lakes in Florida were shown by Kenner (1964). Six of these lakes are in Orange County. ALTITUDES At its lowest level, Lake Cone, a widening of the St. Johns River, was only about 2 feet above msl. A small lake near Tangerine is shown on the U. S. Geological Survey topographic map to be at an altitude of 158 feet. The altitude of a lake's surface seldom remains constant very long. Figure 16 shows the percent of time that specific altitudes were equalled or exceeded for selected lakes in Orange County. SEASONAL PATTERNS IN LAKE-LEVEL FLUCTUATIONS Lake levels fluctuate in response to the net differences between rainfall and evaporation with modifications by surfaceand ground-water inflow and outflow. Table 1 shows the monthly averages and extremes of rainfall at Orlando and figure 34 shows the estimated monthly averages of evaporation from lakes in Orange County. Average monthly evaporation from lakes in Orange County was computed by multiplying average pan evaporation at Orlando as determined by the Weather Bureau by monthly coefficients determined from evaporation studies at Lake PAGE 89 WATER RESOURCES OF ORANGE COUNTY 75 8 7 6 w V) C5 5.............................. z z -4 0 w S--O 0 J F M A M J J A S O N D Figure 34. Estimated average monthly evaporation from lakes. Okeechobee between 1941 and 1946 (Kohler, 1954). Departures of lake evaporation from average are small in comparison to departures from average in rainfall. Figure 35 shows the monthly average change in stage of three lakes in Orange County in comparison with the monthly differences in the average rainfall and average evaporation. In general, when the difference is PAGE 90 0 .4 ....., 0.3 B M A B M A B M A B M A B M -1 M W 0. --0. -0.2 -4-0 -0.3 _ _ _ _____ -g -0.4 ----------------------------------------------------1 W. A-LAKE APOPKA B-LAKE BUTLER M-LAKE MAITLAND 0.3 WW 0.2 --------|li ---IWW w 0.2 z w -0,1 <> JAN. FEB. MAR. APR. MAY JUNE JULY AUG. SEPT. OCT. NOV. DEC.. Figure 35. Comparison of average monthly change in stage of three lakes with average monthly difference in rainfall and evaporation at Orlando. PAGE 91 WATER RESOURCES OF ORANGE COUNTY 77 negative (rainfall less than evaporation), the lake levels fall, and when the difference is positive (rainfall more than evaporation), the lake levels rise. The levels of lakes with surface outlets normally decline in October despite a slight excess in rainfall over evaporation because of large surface outflow when the lakes are high. Other factors such as manipulation of control structures may account for inconsistencies like the behavior of Lake Maitland in December and January and Lake Apopka in June. RANGE IN LAKE-LEVEL FLUCTUATIONS All of the lakes in Orange County receive about the same number of inches of rainfall on their surfaces and lose about the same number of inches of water by evaporation from their surfaces; yet the range in fluctuation of their levels varies widely from lake to lake. Differences in the physiographic features of the individual lakes and in some cases, control and use of the lake water account for this wide variation in range of fluctuation. The physiography of a lake determines how each of four processes (surface inflow, surface outflow, underground inflow, and underground outflow) will affect its level. The relationships of these processes to lake levels is extremely complex. The degree of imbalance between inflow and outflow determines the range in fluctuation. A specific change in a lake's level can be brought about either by a small imbalance occurring over a long period or by a large imbalance occurring over a short period. To further complicate matters, the same lake may be affected by different combinations of factors at different times. In Orange County the lakes having the greatest range in fluctuation are those effectively connected to the artesian aquifer in areas where the piezometric surface has a large range in fluctuation. Lake Sherwood, whose range in stage is the greatest observed in Orange County (22.4 feet) is an example. The surface drainage from about 2,400 acres and ground-water seepage from the water-table aquifer in the surrounding sand hills enter Lake Sherwood from which the only escape is by evaporation and downward seepage into the underlying artesian aquifer. The rate at which the downward seepage occurs depends on how high the lake level is above the piezometric surface. In September 1960, the piezometric surface at Lake Sherwood rose to 85 feet and inflow was so great that the lake level rose to above 88 feet before equilibrium between gains and losses was achieved. By June 1963, PAGE 92 78 REPORT OF INVESTIGATIONS NO. 50 the piezometric surface had fallen to about 62 feet and a lake level of only 64.7 feet produced equilibrium between gains and losses. Generally lakes having the least range in fluctuation arc those Swhose levels are mainly affected by the water table in areas of relatively flat terrain. Lakes Silver and Corrine are examples. These lakes have relatively impermeable bottoms. Their levels are always high above the piezometric surface which has no effect on them. Surface inflow is small in comparison to the size of the lakes and they have surface outlets which readily remove excess water. During droughts seepage into the lakes from the relatively stable water-table aquifer tends to offset evaporation losses. These characteristics tend to reduce the difference in the rates of gains and losses so that ranges in fluctuation are small. In areas where the range of fluctuation of the piezometric surface is small, the range in fluctuation of a lake is small, no matter how effective its connection to the artesian aquifer. WATER QUALITY IN LAKES In general, the water in lakes in Orange County is of suitable chemical quality for most purposes, however, in some lakes hardness, high color, low pH, and other factors limit the usefulness of the water. An exception is the water in Lake Poinsett at the southeastern corner of the county which becomes so highly mineralized during extended droughts due to inflow of salty artesian water that it is not useful for many purposes. One or more water analyses were made from 12 lakes in the county during the investigation (figure 13). Four lakes were sampled several times during high and low stages; the results of the analyses of these samples are summarized in table 8. The water in Lake Francis near Plymouth has the lowest mineralization and Spring Lake at Orlando has the highest mineralization except for Lake Poinsett. Table 12 gives analyses of Lake Francis and Spring Lake. The mineral content of the water in Lake Francis is low because the surrounding hills are composed of clean, practically insoluble sand which allows the rain to seep rapidly to the lake without becoming very mineralized and because downward leakage to the artesian aquifer prevents a buildup of mineralization. The relatively high calcium, sodium sulfate, and chloride concentrations in water from Spring Lake indicate that some pollution occurs. The sodium, sulfate, and chloride concentrations are all higher than they are in surface or ground PAGE 93 TABLE 12. ANALYSIS OF WATER FROM LAKE FRANCIS AND SPRING LAKE. Chemical analyses, parts per million except Specific Conductance, pH and Color. Hardness U as CaCO 0 47 Lake Francis near Plymouth 7-24-63 0.1 .06 2.8 4.1 5.7 1.2 2 12 11 .2 0.0 38 24 22 71 5.0 10 42 Spring Lake at Orlando 66-62 1.2 .00 32 6.8 18 4.5 96 34 22 .3 .4 166 108 30 300 7.0 10 2 PAGE 94 80 REPORT OF INVESTIGATIONS NO. 50 water in the Orlando area. Runoff from fields that are fertilized and drainage from septic tanks contribute to pollution in the lake. Water from Lake Hart near Narcoosee (station 21), has been analyzed semiannually since October 1954 (See table 8). This water has high color, low pH values, and low dissolved mineral content. Lake Hart is in a swampy area which contains much decaying organic material which causes the high color in the water. Decaying organic material usually contains weak organic acids which cause low pH. The mineral content of the water is low because the soil in the area is relatively insoluble. The color during the period of record ranged from 30 to 170 units. The pH ranged from 5.4 to 6.3, indicating that the water is slightly corrosive. The dissolved mineral content ranged from 20 to 52 ppm. The water in Lake Apopka at Winter Garden (station 5) is hard and high in calcium bicarbonate, indicating inflow of water from the Floridan aquifer. During low stage in February 1963, the calcium content was 28 ppm, the bicarbonate was 156 ppm, and the water hardness was 150 ppm. The range in quality of water from Lake Apopka in table 8 shows other constituents in concentration that are higher than those in water in the Floridan aquifer near Lake Apopka. Possible sources of these constituents are waste water from nearby citrus processing plants, sewage plant and septic tank effluent, and leaching of fertilizer and pesticides applied to lands within the lake basin. Water collected from Johns Lake at Oakland (station 25) at low stage in 1963, had a hardness of 44 ppm, a mineral content of 111 ppm, and a color of 25 units. This relatively high mineralization is probably caused by some of the fertilizer that was applied to the surrounding groves entering the lake through surface runoff and seepage of ground water. CONTROL OF LAKE STAGES The logical approach to control of lake levels is through control of the factors that affect them. These factors are: rainfall, evaporation, surface inflow and outflow, and underground inflow and outflow. However, rainfall and evaporation cannot be effectively controlled. Control of lake levels through control of surface inflow has been practiced in Orange County for years. For example, water that would normally drain from Colonial Plaza into the south Orlando lakes is diverted to Lake Sue through a pipeline. Much water that would otherwise enter lakes from street drainage is PAGE 95 WATER RESOURCES OF ORANGE COUNTY 81 diverted to the artesian aquifer through drainage wells. However, during extremely wet years, such as 1960, flow into these wells when added to the normal recharge raises the piezometric surface so that the wells in some lakes refuse to take water and some wells even discharge water into the lakes. Surface outflow from a lake may be conveyed in open channels and culverts or pumped out through pipes. Conceivably, open channels can be used to drain any of Orange County's lakes. However, gravity drainage of many of the landlocked lakes would be expensive because of the depth and length of channel excavation required. For instance, to drain Lake Sherwood through an open channel would require a channel more than 10 miles long with cuts up to 45 feet deep. The channel would, of course, provide drainage for those intervening lakes through which it could be routed, but it might drain some of them dry. Open channels require considerable maintenance; they require wide rights-of-way; they are often unsightly; and they break up the continuity of the land; they interfere with land transportation; and they may add to water-control problems elsewhere by introducing water where there is already an excess. A combination of open channels, culverts, and pumps can often be used to advantage. Artesian wells can be used to remove water from or to put water into a lake. If the lake level is higher than the piezometric surface, water from the lake will flow into the well; if the piezometric surface is higher than the lake level, water will flow out of the well. The natural direction of flow can, of course, be reversed by using pumps; however, pumping of water down drainage wells is prohibited by State Board of Health regulations. PROBLEMS Surface-water problems in Orange County stem from two main causes-floods and water deficiency. Types of flooding that occur in Orange County are: (1) floods resulting from surface runoff which are short-lived, and (2) floods resulting from high ground-water conditions which persist much longer. Type 1 floods are far more frequent than type 2 floods. Type 1 floods are confined to areas contiguous to streams and lake depressions that have large surface inflows. Type 2 floods are confined mostly to lake flood plains, "Bottoms" in closed basins and reach a peak at about 6-year intervals. Because of the long duration PAGE 96 82 REPORT OF INVESTIGATIONS NO. 50 of type 2 flooding, the county often suffers soil moisture deficiencies at high-ground locations while lakes remain flooded in other areas. The bed slopes of the streams that drain Orange County are so slight that velocities are not sufficient to cause appreciable erosion of the vegetation-filled channels. Consequently, the channels have not cut to depths that are below the water table when it is at even moderately low levels. Because of this most of the streams either cease flowing or recede to extremely low flow after only about 90 days of drought. To date, problems associated with low flow have been minimal in the country; but as the population and industrial complex expand, the need to dispose of wastes by way of streams may become more pressing. Because streamflow is small or nonexistent a large part of the time, streams cannot be used to transport wastes without becoming excessively polluted unless their base flows are improved or augmented. The base flow of a stream can be increased by deepening its channel to intercept the water table during droughts and cutting lateral ditches from the channel to increase the length of channel exposed to seepage. This would, of course, lower the water table adjacent to the channel and lateral ditches, but it would also improve the conveyance of the channel and the increased channel capacity would tend to reduce the height of flood crests. The flow of the streams could be augmented with water pumped from the artesian aquifer. GROUND WATER Ground water is the subsurface water in the zone of saturation -the zone in which all the openings of the soil or rock are completely filled with water. The source of all natural fresh ground water is precipitation which in Florida is almost entirely rain. Ground water in Orange County occurs under nonartesian and artesian conditions. Nonartesian conditions occur when the upper surface of the zone of saturation (the water table) is not confined and, accordingly, is free to rise and fall directly in response to variation in rainfall and discharge. Artesian conditions occur where the water is confined and rises in wells above the point at which it is first penetrated. NONARTESIAN AQUIFER The nonartesian aquifer extends over most of the county and is composed mainly of quartz sand with varying amount of clay, PAGE 97 WATER RESOURCES OF ORANGE COUNTY 83 hardpan and shell. In most parts of Orange County, the base of the aquifer is approximately 40 feet below the land surface. However, in parts of the highlands region, the nonartesian aquifer may extend to greater depths. Its permeability and thickness and, consequently, its productivity vary; and there are local areas where it does not yield much water. Most wells in the nonartesian aquifer are small diameter, sand-point or screened wells 20to 30-feet deep that yield sufficient water for domestic use (5 to 10 gpm). In some areas open-end wells can be constructed by seating the casing in a hardpan or clay layer and then drilling through the hard layer and pumping out stand until a small cavity or "pocket" is formed below the hardpan or clay layer. The well is then pumped at a rate higher than the planned normal rate until it is virtually sand free so it will not yield sand when in normal use. Wells of this type usually yield more water (up to 30 gpm) and require less maintenance than sand-point or screen wells; but, in many areas of the county, geologic conditions are not favorable for their development. WATER LEVELS The water table in Orange County ranges from about 0 to 20 feet below the land surface except below some of the sand hills in the western part of the county where it may be considerably deeper. In the lowlands and flatwoods sections of the county, the water table is usually within a few feet of the land surface. The water table conforms in a general way to the configuration of the land surface, but it is usually at greater depths under hills and may be above the land surface in low swampy areas. The degree to which the water table conforms to the configuration of the land surface depends to a large extent on the permeability of the nonartesian aquifer and the materials below it. Other factors being equal, the water table follows the land surface closest where the permeability is least. The water table fluctuates in response to changes in recharge and discharge in a manner similar to the fluctuation in the levels of lakes and reservoirs. Fluctuations of the water table range from a few feet in flat areas of the county to 15 feet or more in hilly areas. Figure 36 shows the water table fluctuation in a well on East Highway 50,-about 1 mile east of Bithlo (well 832-105-3) and in a well on Hiawassee Road about a mile south of West Highway 50 (well 832-128-4). The hydrographs show that the Bithlo well fluctuated about 4.5 feet during the period of record while the PAGE 98 5 I I I I I I -------J (Ai 0 Bithlo well 832-105-3Z Depth 15 feet ,-, -Screened 3 feet n: Depth 40 feet O I pen end S25 a 0 -o J FM A M J J A S O N D J FM AM J J AS 0 N D J F M A M J J A SO 0 N D J F M A M J J A S 0 N.D 1960 1961 1962 1963 Figure 36. Hydrographs for wells near Bithlo and Hiawassee Road showing patterns of fluctuations of the water table. IL pe n 3 2_ -.-S ,l l l l -------Js / aw -/^ patterns of fluctuations of the water table. PAGE 99 WATER RESOURCES OF ORANGE COUNTY 85 Hiawassee well fluctuated about 16 feet. The hydrograph of the Hiawassee well is much smoother than the Bithlo well hydrograph, partly because the Hiawassee well is measured only once a month, whereas the Bithlo well has a continuous recorder and is plotted six times a month; but mostly because the water table is close to the land surface at the Bithlo well whereas it is 21 to 37 feet below the surface at the Hiawassee well. At Bithlo the water table reacts quickly to local showers and with prolonged rainfall quickly rises to the land surface where surface runoff occurs. During drought the water table quickly declines to a few feet below the land surface because surface drainage and evaporation can rapidly remove the water. However, once the water table is 3 or 4 feet below the surface, further decline is very slow because the streams have very shallow beds and cease to flow, evaporation practically ceases, and transpiration diminishes because most vegetation is shallow rooted. Also, lateral ground-water flow from the area is very slow because of the flat terrain; and downward leakage into the underlying artesian aquifer is slight because of the thick section of relatively impermeable marl and clayey sand that separates the nonartesian and the artesian aquifers. At the Hiawassee well the water table is always 20 feet or more below the land surface. Rain filters slowly through the overlying sand, and the response of the water table to heavy rainfall or drought usually lags about a month. The water table fluctuations in this area reflect long periods of excessive and deficient rainfall. Brief showers after a dry period have little or no effect on the water table because the rain is held as soil moisture and returned to the atmosphere by evaporation and transpiration. However, the surface sands rapidly absorb even a heavy and prolonged rainfall and no surface streams flow from the area. The water that infiltrates below the root zone eventually seeps to the water table. After the water reaches the water table, it either seeps into nearby lowlying ponds (which occur to a considerable extent during periods of excessive rainfall) or it seeps downward into the artesian aquifer through the relatively thin and permeable clayey sand that separates the nonartesian and artesian aquifers. During droughts most of the ponds in the Hiawassee area go dry and the water table is mostly below the root zone, so it is apparent that further decline of the water table is due mostly to downward leakage into the artesian aquifer. The fluctuations of the water table in the Bithlo and Hiawassee wells reflect only natural changes as there is no appreciable pumping or irrigation in their vicinities. PAGE 100 86 REPORT OF INVESTIGATIONS No. 50 RECHARGE Most natural recharge to the nonartesian aquifer in Orange County comes from rain within or near the county. Some recharge comes from upward leakage of water from the artesian aquifer in areas where the piezometric surface is above the water table and from seepage from streams in areas where the streams are higher than the surrounding water table. Artificial recharge to the nonartesian aquifer occurs by infiltration of water applied for irrigation, discharge from septic tanks, and by discharge from flowing wells. Most of Orange County is blanketed with permeable sand which allows rain to infiltrate rapidly. In much of the eastern and southern parts of the county, where the land is flat and the water table is near the surface, the overlying surfaces and is quickly saturated during the rainy season; and the excess collects in swamps and sloughs or runs off in streams and rivers. In much of the western part of the county, the water table is far below the surface except in depressions. The surface sand can absorb rainfall at a rate of as much as 3.5 inches per hour with little or no direct surface runoff (Powell and Lewis, open-file report), and the large volume of sand above the water table holds large quantities of water which percolates slowly to the water table. DISCHARGE Discharge from the nonartesian aquifer in Orange County is by evapotranspiration, seepage into surface-water bodies, downward leakage to underlying aquifer, pumpage, and seepage into neighboring counties. Ground water is removed from the zone of saturation and from the capillary fringe by the roots of plants and is given off to the atmosphere by transpiration. The depth to which plant roots penetrate depends on the type of plant and the soil, and ranges from a few inches to 50 feet or more for certain types of desert plants. In Orange County the maximum depth of tree roots is about 15 feet whereas the water table in most of the county is less than 15 feet below the surface; therefore, discharge of nonartesian ground water to the atmosphere by transpiration is appreciable. Where the water table is near the land surface, ground water moves upward by capillary action through the small pores in the soil to the surface and evaporates. The rate of evaporation varies PAGE 101 WATER RESOURCES OF ORANGE COUNTY 87 with the depth to the water table, the porosity of the soil, the climate, the season and other factors. The base flow of most streams in Orange County is maintained by seepage from the nonartesian aquifer. Seepage from the nonartesian aquifer also helps to maintain the levels of lakes and ponds during droughts. Practically all natural recharge to the -Floridan aquifer in Orange County passes through the nonartesian aquifer. In the western part of the county, downward leakage is probably the principal form of discharge from the nonartesian aquifer. Seepage of nonartesian water out of the county is probably small. Water is pumped from the nonartesian aquifer for lawn irrigation, stock watering, and domestic use. Most wells are small 11/4to 2-inch sand-point wells which yield about 5 to 10 gpm. QUALITY OF WATER Several factors influence the quality of the nonartesian ground water in Orange County. Rain recharging the aquifer dissolves soluble material contacted such as fertilizer and insecticides. Drainage from septic tanks percolates to the nonartesian aquifer. Harmful bacteria and color are usually removed if the recharge water percolates through sand. Some of the very shallow wells located in swampy areas yield water with high color. Most of the nonartesian ground water that is soft and low in mineral content has low pH indicating that it is corrosive. In areas where the piezometric surface is above the water table, upward leakage occurs and the nonartesian water is more highly mineralized. The dissolved mineral content of water from wells in the nonartesian aquifer varies greatly depending on the composition of the aquifer. The water from wells developed in clean quartz sand is usually very soft (hardness generally less than 25 ppm) and low in mineral content (about 25 to 50 ppm). The following is a typical analysis of water from a well in western Orange County (838-128-1) developed in clean quartz sand: Silica (SiO2) 2.5 ppm Dissolved solids 21 ppm Iron (Fe) .45 ppm Specific conductance 39 micromhos Calcium (Ca) .8 ppm at 25°C Magnesium (Mg) .7 ppm Bicarbonate (HCO,) 5 ppm Sodium (Na) Sulfate (SO,) 2.8 ppm Potassium (K) .0 ppm Chloride (Cl) 5.5 ppm Fluoride (F) 0.1 ppm pH 5.2 units PAGE 102 88 REPORT OF INVESTIGATIONS No. 50 Nitrate (NO3) .0 ppm Color 8 units Hardness as CaCO, 5 ppm The relatively high iron content (.45 ppm) was probably due to iron dissolved from the casing or pump by the water of low pH (5.2). The water from a well (832-101-2) at Christmas in eastern Orange County had an iron content of 4.5 ppm. This high iron content probably came from the aquifer because the neutral pH of the water, 7.0, indicates that it is not corrosive. Total mineral content as high as about 500 ppm andhigh concentration of some constituents indicate that the water in some wells in the nonartesian aquifer is polluted. The water from a well (822-138-3) in the southwestern part of Orange County had a dissolved mineral content of 530 ppm (estimated from a conductivity measurement). Concentrations of other constituents were potassium, 10 ppm, sulfate, 107 ppm, and nitrate, 173 ppm, which definitely indicates a nearby source of pollution. Use of water containing an excess of about 45 ppm of nitrate for feeding formulas for infants results in metheglobinemia or cyanosis (blue babies) in the infants. The water from some of the shallow wells had as much as 90 units of color. SECONDARY ARTESIAN AQUIFERS Several secondary artesian aquifers occur locally within the confining beds of the Hawthorn Formation and less extensively within the formations above the Hawthorn. These aquifers are usually found at depths ranging from about 60 to more than 150 feet below the land surface and are composed of discontinuous shell beds, thin limestone lenses or permeable sand-and-gravel zones. The secondary artesian aquifers are most productive in tthe area east and south of Orlando where they generally yield sufficient water for domestic use. Open-end cased wells can sometimes be constructed in the secondary artesian aquifers, but screens are often necessary to keep sand from the well and to obtain sufficient water. WATER LEVELS A continuous record of the water levels of a secondary artesian aquifer have been recorded in a well about 1 mile east of Bithlo PAGE 103 WATER RESOURCES OF ORANGE COUNTY 89 (832-105-2), figure 37. The casing of this well extends 75 feet below land surface into a 12-foot shell bed. At this site there is also a record of the fluctuations of the water table (well 832-105-3) and the fluctuations of the piezometric surface of the Floridan aquifer (well 832-105-1). The water level of the secondary artesian aquifer is always below the water table and above the piezomtric surface of the Floridan aquifer at this site. This relation probably exists wherever the water table is continuously above the piezometric surface. At this location the secondary artesian water level is 6 to 12 feet below the water table and 6 to 14 feet above the water level in the Floridan aquifer. The range of fluctuation of the water level in the secondary artesian aquifer for the period of record was about 31/ feet or from 7 to 101/2 feet below land surface. The secondary aquifer water level does not respond rapidly to rainfall. The recorder chart usually shows very little daily fluctuation, however there is a gradual long-term decline or 0 ...a, Well 832-105-23' " --Depth 75 feet Screened 3feet Nonortesion aquifer Cased 65 feel 5-S Secondary artesian aquifer Well 632-10-1 Depth 492 feet Cosed 151feet S Floridan aquifer . 25 L 20I -Rainfall Orl6ando 30 --t J FMM SON D FMMJJASONDJ AMJ A S OND J FMAMJ J AS ONDJ FMA MJJ AS OND 1960 1961 1962 1963 Figure 37. Relationship between water levels at Bithlo and rainfall at Orlando. PAGE 104 90 REPORT OF INVESTIGATIONS No. 50 rise that corresponds to general wet or dry periods. This indicates that water enters and leaves the aquifer at a slow rate, and the hydraulic connections to the overlying and underlying aquifers are probably rather poor. RECHARGE Recharge to the secondary artesian aquifers in Orange County is by downward leakage from the nonartesian aquifer in most parts of the county and by upward leakage from the Foridan aquifer where the piezometric surface of the Floridan aquifer is above the piezometric surface of the secondary artesian aquifers. A small amount of water probably flows into the county from secondary artesian aquifers in surrounding counties. The secondary artesian aquifers are the least likely to be polluted because the overlying, low-permeability beds tend to protect them from surface pollution, and drainage wells are usually cased through the secondary artesian aquifer zone. DISCHARGE Water discharges from the secondary artesian aquifers by downward leakage to the Floridan aquifer, upward leakage to the nonartesian aquifer where the piezometric surface is above the water table, underground flow out of the county, and pumpage. QUALITY OF WATER The quality of water in the secondary artesian aquifers in Orange County varies with location, depth, and the local hydrology. In areas where the piezometric surface of the secondary artesian aquifer is below the water table, downward leakage from the water table aquifer occurs and the water tends to be similar to the nonartesian water except where additional solution has taken place within the aquifer. In areas where the piezometric surface of the Floridan aquifer is higher than the piezometric surface of the secondary artesian aquifer, upward leakage occurs from the Floridan aquifer and the water in the secondary aquifer tends to be similar to the water in the Floridan aquifer. Generally, the dissolved-solids content of the water in the secondary artesian aquifers ranges from 100 to 400 ppm. The predominating ions usually are calcium and bicarbonate. Water from secondary artesian aquifers is sometimes more mineralized than is water from the Floridan aquifer. For example: The water o' PAGE 105 WATER RESOURCES OF ORANGE COUNTY 91 from a 75-foot deep well at Bithlo (832-105-2) constructed in a secondary artesian aquifer had a dissolved solids content of 380 ppm. The water from an adjacent 492-foot deep well in the Floridan aquifer had a dissolved solids content of 290 ppm. FLORIDAN AQUIFER The principal artesian aquifer in Orange County is part of the Floridan aquifer that underlies all of Florida and parts of Alabama, Georgia, and South Carolina. The Floridan aquifer, as defined by Parker (1955, p. 189) includes "parts or all of the middle Eocene (Avon Park and Lake City limestones), upper Eocene (Ocala limestone), Oligocene (Suwannee limestone), and Miocene (Tampa limestone) and permeable parts of the Hawthorn formation that are in hydrologic contact with the rest of the aquifer." AQUIFER PROPERTIES The Floridan aquifer is one of the most productive aquifers in the country. In Orange County many large diameter wells (20 inches or more) yield more than 4,000 gpm. These wells can be constructed in almost any area of the county. Wells that will yield only small quantities of water are usually in the vicinity of sinkholes where sand has filled solution channels in the aquifer. Pumping rate-drawdown ratios range from less than 100 gpm per foot of drawdown to over 500 gpm per foot of drawdown. The aquifer consists of nearly 2,000 feet of porous limestone and dolomite or dolomitic limestone covered by sand and clayey sand ranging in thickness from a few feet to about 350 feet. The altitude and configuration of the top of the Floridan aquifer is shown in figure 38. The depth below land surface to the top of the aquifer is shown in figure 39. The total thickness of the aquifer is not accurately known because the deepest water well in the county penetrates only the upper 1,400 feet. The log of an oil test hole drilled southeast of Orlando shows dense anhydrite at about 2,000 feet, and this is assumed to be the base of the aquifer. The lithologic and hydrologic character of the Floridan aquifer is not uniform either horizontally or vertically. In general, there are alternating layers of limestone and dolomite or dolomitic limestone. The limestone layers are usually softer and of lighter color than the dolomitic layers. The aquifer stores huge quantities of water and also acts as a conduit. Water moves slowly through PAGE 106 5 40 35 30 25 id IB 10 o a' a*O ' ' 8at0 ~t -EXPLANATION o oOLA NOU L AA K E COUNTY N " ) T Yi T.. * * *^ "o"'" -, ý,A' o .0,_ INkoo -"%slow. --.... ..o .".'. J . l wull 0or -l, I 0 146 b$ p 04 JRalANO O e almew Can0 0. 0 0 ., 0 0 a A b co, ,Cl ooJ m~n 1e 0 1 0 01 a " -.0 S8 0 C 0 i i Ong Count o Flrd., ,\ I ^ ,,"P ° ~ -ast.Ilill \ -i"1 .0 o 11) '? 1 .11 °n\ \ '''*,fr.'° -P .... P _ .*L ...... .O U N T Y , S30 10 05' ' Be ken0from U.S.Geoooglicl 0 I a 3 4 ) e 7 8 e*10mles Survey topographic quadranglei Figure 88. Configuration and altitude of the top of the Floridan aquifer in Orange County, Florida. ·~) .\· 0 PAGE 107 S40' 35' 30' 25' 20' 15' I0', 05' 800' 55' 80V0' 1 EXPLANATION -LAKE COUNTY N -°. 0 Ti sL 0 CO 10T e_ N s-i .7" o 0 // 00 4. ......' ' Showt the O/h ;V the 10 of h 'o 0 -45' Igol /00 tI W h 3 tOOt -4/onr de'. sf -0 ro SNEToo Ao Cnr o i -3 ' 0 o 0 k SCg or/RLANo "__ 0 U 0NY -'oske o o ° / § °° in\ Org C n o 0 c ° o , T ' O '4 u -0 '-P 0 L K o s' L A '' ,Y -0' 10 a 10 40 30 o 15t 05 ' 0 0 Base kahkn from U. S. Geological 0 1 2 3 4 5 6 7 8 9 10 miles urvey topogrophic quoadrongles, iI , W, Figure 39. Depth below land surface to the top of the Floridan aquifer in Orange County, Fla. -Mly~eCuny Fa PAGE 108 94 REPORT OF INVESTIGATIONS NO. 50 the rock from areas of recharge to areas of discharge. The entire aquifer has been affected to some degree by the dissolving action of ground water and is somewhat analogous to an enormous sponge. Some of the largest known caverns in Florida have been found within the Floridan aquifer in Orange County. One of the largest caverns with no opening to the surface ever discovered in Florida was encountered in a city supply well drilled in the southwest part of Orlando. This cavern was 90-feet high with the ceiling 578 feet below the land surface. The cavern was filled with water and there was 12 feet of black organic muck on its floor. The areal extent of this cavern is unknown, but several deep wells 1,000 feet to the north did not penetrate it. One of the deepest and largest known caverns in Florida is a sinkhole near Little Lake Fairview, northwest of Orlando, known as Emerald Springs. Emerald Springs was measured in 1956 and found to extend 884 feet below the water surface which is about 45 feet below the surrounding land surface. According to divers who have explored the sinkhole, it has sloping sand-covered sides for 45 feet below the water surface and then a vertical neck, about 20 feet in diameter, through limestone for about 45 feet. Below this depth, there is a large room with a sloping ceiling. The wall of the room was found at a distance of 89 feet in one direction but had not been found at a distance of 100 feet in the opposite direction (when the divers were forced to return to the surface). Zones of the Aqulfer The Floridan aquifer in central Orange County has two major producing zones that are separated by a relatively impermeable zone. The upper producing zone extends from about 150 feet below the land surface to about 600 feet. The lower producing zone extends from about 1,100 feet to 1,500 feet or more below the land surface. Both major producing zones are composed of hard brown dolomitic limestone or dolomite and relatively soft cream limestone; however, the top half of the upper zone is mostly soft limestone. Some of the dolomite in botlh major producing zones is very dense, but many interconnecting solution cavities make the overall permeability of both zones very high. The limestone in the top half of the upper zone is mostly white, soft, granular. and fossiliferous. This limestone contains cavities, but they are usually neither as large nor as numerous as the cavities in the dolomitic parts of either major producing zone. At PAGE 109 WATER RESOURCES OF ORANGE COUNTY 95 some locations, very large (4,000 gpm or more) yields can be obtained from the limestone, but most high yield wells also penetrate the underlying dolomitic limestone. However, many domestic wells and small public supply wells draw all their water from the limestone section of the upper zone. The municipal supply wells for the Cities of Orlando and Winter Park are developed in the lower (1,100-1,500 feet) producing zone. These wells generally yield 3,000 to 5,000 gpm with 10 to 25 feet of drawdown. The relatively impermeable zone (600 to 1,100 feet below the land surface) separating the two major producing zones is composed of layers of relatively soft, mealy limestone and dolomitic limestone. It contains some water-bearing layers, but generally this separating zone yields much less water than the zones above and below it. In many parts of the country the separating zone would be considered a good aquifer; but because much larger supplies can be obtained above and below this zone in Orange County, very few wells are developed in it. The occurrence of reported cavities is shown in figure 40. The number of cavities shown for different depths actually does not represent t the true distribution of the cavities because many more wells penetrate the upper part of the aquifer than penetrate the lower part. However, the illustration does show that although cavities have widespread vertical distribution, they are more prevalent in some zones than in others. Interrelation of Zones The interrelation of the upper and lower producing zones is of vital importance to the people of Orlando and Winter Park because excess surface water is disposed of in the upper zone while most of the municipal water supplies are developed from the lower zone. Contaminated water can enter the upper producing zone through the numerous drainage wells (See section on drainage wells, page 83) and it is important to know if this contaminated water can move into municipal supply wells. It has been postulated that some dense dolomitic beds between 400 and 600 feet in the upper zone might be continuous and act as an impervious layer to protect the lower zone. To test this idea, a well was drilled at Lake Adair in Orlando into the upper zone of the aquifer adjacent to an existing well in the lower zone. The shallow well is cased to the top of the aquifer (105 feet) and bottomed at the top of the hard dolomitic zone at 400 feet. The PAGE 110 96 REPORT OF INVESTIGATIONS NO. 50 200 --m -----nInn, 1 I 0 -200 -300 W -400 I I -400 S-600oo EXPLANATION a-800 WellOrange County, Fla.vity SCavity tons -1000 -1100 -1200 -1300 Figure 40. Distribution of reported cavities in Floridan aquifer in Orange County, Fla. PAGE 111 WATER RESOURCES OF ORANGE COUNTY 97 deep well is cased to 601 feet and bottomed at 1,281 feet. Automatic water level recording gages were installed on each well to compare the fluctuation of the water levels in the two zones in response to hydrologic changes. If the two zones were effectively separated, the water levels should respond differently to local hydrologic changes such as pumping and rainfall. Figure 41 shows that the water levels in the two zones are almost identical when the water levels are stable or slowly declining. Both zones react rapidly to local rainfall, but the rise in the upper zone is usually about twice the rise in the lower zone. After the rain, the upper zone declines more rapidly than the lower zone so the two levels again approach each other. This indicates that the two zones are somewhat separated; but given time and a difference in pressure head, water will move from one zone to the other. Further evidence of interconnection of the two zones is shown by the hydrograph of an observation well at the Orlando Air Force Base (well (833-120-3). This well is about 11/ miles north of the S12 Well 833-123-10 Depth 400 feet o Cased 105 feet Upper Zone I sed to 601 feet z 17---------I I I I IA --327 Well 833-123-1 W eDepth 1245 feet Cased to 601 feet S32 Lower Zone s 5---------J -^ H ---J FMAM JJASOND JFMAM J J S ON D JFMAMJ J ASON 1962 1963 1964 Figure 41. Relationship between water levels in the upper and lower zones of the Floridan aquifer at Orlando. PAGE 112 98 REPORT OF INVESTIGATIONS NO. 50 Orlando Utilities Commission well field (two wells) at Primrose and Church and about the same distance east of the Commission's Highland well field. The observation well is 655 feet deep and cased to 383 feet, whereas the supply wells are about 1,200 to 1,500 feet deep and cased to about 1,000 feet. A comparison of pumping times in the well fields with minor fluctuations in the water levels in the observation well shows a direct and immediate correlation (See figure 42.). Each time a pump in either well field was turned on or off a sharp change occurred in the water level in the observation well. This indicates a good connection between the upper and lower zones. The water level in the lower zone in the vicinity of Orlando was always somewhat below the level in the upper zone in 1963-64 because an average of about 25 million gpd (gallons per day) was withdrawn from the lower zone and was replaced by leakage through the overlying beds. Also, several hundred drainage wells discharged water directly into the upper part of the aquifer in 8125' 24' 23' 22' 21' 20' 8119' 2835' N 34' --iHighlond * Obervon wgla 1 well . well fild 833-120-3' 33' S ' Primrose 59.5O ) well fields. 32' ... .. If .28031 I0 1 2 Mile ..Observation Well 833-120-3 V L 0 60.5 8U M 6 -.0 cr co 2 3 4 5 6 MARCH,1964 Figure 42. Hydrograph of well 833-120-3 showing effects of pumpage in the Orlando well fields. PAGE 113 WATER RESOURCES OF ORANGE COUNTY 99 addition to the natural leakage that occurred through the overlying confining beds. Figure 43 shows the altitude and configuration of the piezometric surface of the lower zone in June 1962. The altitude and configuration do not differ materially from the altitude and configuration of the piezometric surface of the upper zone in May 1962 (See figure 5.) indicating that both zones are connected and are recharged in the same general area. Chemical analyses of the waters from the two zones tend to support the conclusion that the two zones are interconnected. Figure 44 shows that there are no significant differences in the chemical quality of the waters in the two dolomite zones. All available evidence indicates that, given sufficient time and pressure head differences, water will move from any part of the aquifer to any other part carrying with it any soluble, long-enduring pollutants it might contain. If heavy pumping creates a deep, permanent cone of depression in the lower zone and pollutants such as hard detergents are present in the upper zone, the pollutants will tend to migrate to the lower zone. 810301 25' 20' 81015' 28°40' I I l lIEXPLANATION 051 Observation well SEMINOLE COUNTY Number indicoles height of --------------water level, in feet above ORANGE COUNTY meon sea level. -4644 Piezometric contour 4 Contour intervol I foot. 35' -O 1R A I oLNo 50 48 28.30' Figure 43. Configuration and altitude of the piezometric surface in the lower zone of the Floridan aquifer in the Orlando area. PAGE 114 100 REPORT OF INVESTIGATIONS NO. 50 0 0 ' * * 0* * 0 100 * * * 200 300 4* S--o ... ..----..... .........-. 5 400 6000 1100 1200 1100 0 100 200 300 400 500 0 too 200 300 * * * 0 *0 0 ,1400 ----'. _e_____ -1 -00 0 100 200 300 400 50 0 100 200 300 OISSOLVED SOIOS, IN PARTS PER MILLION HARDNESS, IN PARTS PER MILLION Figure 44. Relation between dissolved solid and hardness of water and depths of wells in the Orlando area. JI PAGE 115 WATER RESOURCES OF ORANGE COUNTY 101 PIEZOMETRIC SURFACE The artesian pressure or piezometric surface is the height to which water will rise in tightly eased wells that penetrate the artesian aquifer. Where the water table is above the piezometric surface, nonartesian water may infiltrate through the confining layer and recharge the artesian aquifer. Conversely, where the piezometric surface is above the water table, the artesian water tends to discharge upward. The piezometrie surface and flowing well areas in Florida are shown in figure 45. The piezometric surface of the Floridan aquifer in Orange County slopes to the northeast and east from its highest point in the southwestern part of the county (figs. 46, 47, 48, and 49). -,·; -^ , .. --.-^ ^, y --------: ___V;_..',,,-j I M A EXPLANATION e ia leevet le en e the silw. 41vtl Is wihlh Willer heta No msý V. In fI ll m ils a We ll thte pei otratloe hl ile? I i letri l e V In r Fl i Cei i nt eIf 1fV iti n t io , o Dihi e iupplemiental lnlgiot o1 10 end 0O , DO tum I mI n to11 i l , th l .. o v .^0 ..-. -$_ , IFigre I 4 isem trisfalioi and «e o alrei .. o... F da alul I ie f eh i Fnal o rid. aJl u ll y 7," L el. Figure 45. Piezometric surface and areas of artesian flow of the Floridan aquifer in Florida, July 6-17, 1961. PAGE 116 4o itJ 10 '' i i i S 1 1 1 1 ; 1 1 1 1 45 -I \ 4\\\ 'i / W .1, 011,l onf * tl bgOkll 45I I Dun fto -Wol nin godly s.5r4nwi chuini i I , ll h IISl , S mS #? .,UPm MaW l 'lomma m is fw, ? mmw i , thir aM ig &W COO 0Sl , 11 4* h1 1,,1 * Nw, -ows / "" LS '^ V" M N "o Im * j S * 9 .ta5LEw --T Y .. ... \ ----"'----N'1 .' i 1 r 1 I , 1 1 I I I 253 ' 25' 20g ' ' Figure 46. Contours of the piezometric surface at high-water conditions, "wad .... lo All All~\ \ ' 'K·· '~1/ V 4 , c, \/~rC 20 .41, C 0 ýUNT Y 2 '11 0an.· lO~ PAGE 117 .45' ' 35 30 25' 20' s' id ' eroO' 5 ' 80 I I I I I I I I i I I I I 1 li I I i I I i I I 4 1 a ' S C L C U 1 Y ).EKPL »ION~ A y E t(E Ny o L S'Smw 4ll4l* 4 "'"11 ml, rat in Ilf tB«ld I So " nWll auomd In m grdi; gqo. 4 wm )n um b r His wels ... I" l f l. S rI..ol S d li M. .0.0 u in 401V Us?. -*-II , "A. C0 UNC M Y :T---. C~ w B OK SCEm U.S LAE1I IA 1 N I3 5 4 0 L Ei, ORO .4 0 Figure 47. Contours of the piezometric surface at about normal conditions, July 1961. 20 0 L 9 2d OS C E 20 0 L r, f10' 55 NTY PAGE 118 Marl 40 3 6o' 2' 2 80 ' 0 0C6 f1 5s' , -.EXPLANATION ' L A E COU' TY ' : 45t-j 41 'i 4d ' .z ' c I 02hG 0 U N T Y 0 R4r N0V1,, I ,3" 4'. -r qaBle -^ -& 7 0 S 0 SCE0LA UNTY-CI -LC AT I re S III ..1 ...w. 3F 30r 2 05 R Figure 48. Contours of the piezometric surface at about normal conditions, December 11-17, 1963. PAGE 119 S 4 40 3' r ' 3. 2 2d S' id , OwO SE* a 1 l I I ,I J 1 I i l i J i I1 l EXPLANATION LAKE COUNTY 1N An GE ToD UTi -sSenrwr \t -\ \.1 '/Mo, Li'b..m. /--mwmImep a* 111_ 01 \ \r i t ,i ...i .l t1l l -. 1 ti | Vo mirSi 5, W Doon l mesan %t i . , 1 C , uO'u.u u eal... I ,Itr .uf S ilu E -3% gue 49. Cotours of the pezoete t extreme ate conditions May 1962. 30 C, 20? 4 35 3L 25' 0o S i5 E5 0BiW IL A0 50 Bese Iflentrm USSGeodSIod 6 as Itoere 0mo SLuney lpographic qus nlat Figure 49. Contours of the piezometric surface at extreme low-water conditions, May 1962. PAGE 120 106 REPORT OF INVESTIGATIONS NO. 50 Water moves downgradient from areas of high piezometric level to areas of low piezometric level. In general, the direction of movement, shown by the arrows in the figures, is at right angles to the contour lines, although locally the direction of flow may be different because of differences in permeability such as caused by cavern systems. Figure 46 depicts the piezometric levels in September 1960, the highest observed during the investigation. The high levels of September 1960 equalled or exceeded the highest previous recorded levels which occurred in the early 1930's. Figures 47 and 48 which show the piezometric surface in July 1961 and December 1963 represent about normal conditions; figure 49 shows the piezometric surface in May 1962 when artesian levels were at their lowest for the period of record 1943 through 1963. The relation of the piezometric surface to the land surface is shown in figures 50 and 51. Figure 50 shows the distance above and below land surface of the static water level in tightly cased wells in the Floridan aquifer during extremely high-water conditions (Sept. 1960). Figure 51 shows the distance above and below land surface of the static water level in tightly cased wells in the Floridan aquifer during extremely low-water conditions (May 1962). Fluctuations Gages were installed on six wells in the Floridan aquifer to record the fluctuations of the piezometric surface (figures 37, 41, 52, and 53). In addition, water levels were measured periodically in about 70 wells. Most water-level fluctuations are caused by changes in rates of recharge (mostly rainfall) and/or discharge. However, variation in barometric pressure, temporary loading of the land surface such as by-passing of trains and earthquakes also cause fluctuations. For example, the Alaskan earthquake of March 27, 1964 created a brief surge of more than 10 feet in the water levels of some wells in Orange County. The sharp rises in the water levels in well 833-120-3 at the Orlando Air Force Base (figure 52) and well 932-128-1 west-of Orlando (figure 53) are caused by rapid recharge through the many drainage wells in the area. The nearly equally sharp declines following the rises show that the water mound created by the drainage wells rapidly dissipated through the porous limestone. Although the water probably moves slowly, the pressure is transmitted relatively rapidly to other parts of the aquifer PAGE 121 5' 40' 35' 30' 25' 0' 15' 10 O' 81"00' 5' 80,50' 2 5 I I I I 28I50' .K E COU NY N 45-IEXPLANATION 45 PMrhetfic Conlow B"Fsa fke rldm QGuollrl, U0vOl V t ilw0 Iand dtolo, Sept 1980 IOfllrnl I0 Sfeel.-4d•.. 40 'SEMINOLEn . Lke A N GO T o Apopko C 0 U N T Y 0, 35' 7o K 25a -a Ie I ZVIV', T. '1ItIon to, " o I I I I 7f -' 81045 40 35 30' 2 20' b 0' 05' Ol0' 55 80050' Bose aken Ifrom U 5 Geological 0 I 2 3 4 b 5 7 8 .9 I te0 tle Survey lopogruphic quadrongles Figure 50. Piezometric surface relative to land surface datum, at high-water conditions, September 1960, Orange County, Florida. PAGE 122 S& l 4Q b 30 0 Oý VV0 15d. :M DIAA L Ast COUNTY N . .w wo " 6 w b."r 40 S EMN0LPOLKE' ,O 40 m 30 20 20'O 05'o e0o0 0 M T'Y Sre mtlefomUSGeooqai o i 2 3 4 5 5 7 o 5 Imes Figure 51. Piezometric surface relative to land surface datum, at low-water cnditionR. May I92. Ora.is County. Florida. conditiona. Tvfst.r I'A20-janse Courtiv. P107-idn PAGE 123 WATER RESOURCES OF ORANGE COUNTY 109 tW 11 tl-13B.I OSERVIAON WELL. U.S. GEOLOGICAL SURVEY Flodnt oaulfr 10------------------.----%-----OpIh of well -310 11. Opth olf ra flOh 03f. 0Well 822-13BOOSERVATION WELL, U.S OCLODICAL SURVEY Shtllow sh o d O hqui.(nbor lIleo n) 10------------------DIp h of will 1811. S ---Welt 033-I2O-S UNUSED SUPP.L WELL ORLANDO AIR FORCEC ASE rloro SlI.fer -----Wll 103s.1TS-. UNWUSE IRRIATIOIN W L. H. HENSCHRN Fl oIon Oqulfer SJFl MJJ 0NDJF A JJAO O LL A0 FMA iS Figure 52. Hydrographs of wells. PAGE 124 5' -40 C 1 41 S" , n TTT-T-T-rT---T. r I SC0RAGE COUNTY " -? I it r -, '»» 7 ..... ,M -rO ) -l , C (