hydrologic conditions. The minimum measured flow, 65 mgd, occurred July 24, 1956, during a severe drought. The flow of Weekiwachee River is derived mainly from Weekiwachee Springs. However, the flow of Little Weekiwachee Springs and countless small springs in the channel along the entire length of the river also contribute to the river's flow. The flow of the river about 5 miles downstream from the main springs averaged about 170 mgd from January 1964 to June 1966.
The flow of Chassahowitzka Springs is measured together with the flow from several small springs in the headwaters and the springs in Crab Creek (a small tributary of Chassahowitzka River) at a point in Chassahowitzka River downstream from Crab Creek. The average combined flow for the January 1964-June 1966 period was 90 mgd. The maximum measured flow (127 mgd) occurred May 18, 1966 during median hydrologic conditions. The minimum measured flow (21 mgd) occurred July 8, 1964.
The flow of all the large springs, with the exception of Weekiwachee Springs, is affected by tidal fluctuations in the Gulf of Mexico. Weekiwachee Springs is unaffected because of the high discharge per unit of channel cross sectional area and the elevation of the springs which effectively blocks tidal movement upstream to the springs.
Variation in specific conductance and discharge caused by tidal flow, as measured at the gaging station on Crystal River, is shown in figure 8. Specific conductance measurement is a convenient and rapid way to determine the approximate amount of dissolved solids in water. The greater the specific conductance, the more dissolved solids (high mineral content). Commonly, the amount of dissolved solids(in milligrams per liter) is about 65 percent of the specific conductance (in micromhos). The mineral content of water in Crystal River is due mostly to sodium chloride from sea water; therefore, high conductance indicates high concentration of sodium chloride. The high values of conductance on September 10, 1964, resulted from wind blown tides caused by Hurricane Dora lThe variation in mineral content of water from Homosassa and Chassahowitzka springs caused by salt water migrating upstream on flood tides are about the same as at Crystal River. However, the mineral content of water from Weekiwachee Springs maintains an almost constant value of about 150 mg/I (milligrams per liter), or conductance of about 230 micromhos.
The flows of Crystal River and Homosassa, Weekiwachee, and Chassahowitzka springs vary as shown by the correlation in figure 9. The maximum rate of water movement and total volume of water discharge by these spring-fed rivers is high