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 1953-September 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