REPORT OF INVESTIGATioNS No. 41


not occur more often than once every 15 to 20 years, and then probably will not persist for more than a few months. A flow of 36 mgd was measured at the point of diversion on May 27, 1963, during a period of extreme low flow.
   A dlam to create a retention reservoir along Econfina Creek is being considered. The main purpose of this reservoir would be to raise the water level in the creek and make gravity flow to Porter Lake possible. There would be a usable storage in this reservoir between elevations 80 and 95 feet of about 4,000 acre-feet. This amount of storage would provide 10 mgd for a period of four months. This, added to the natural flow of the creek, would assure a minimum flow of about 40 mgd. A flow of 40 mgd would supply about 0.7 of a foot of water per month on the 5,000-acre lake area.
   If diversion from Econfina Creek is at a rate of 30 mgd, the streamflow just downstream from the point of diversion would be almost depleted during periods of low flow. This effect will diminish downstream. Diversion of 30 mgd would reduce the flow below Gainer Springs about 15 percent. The width of the stream at this point would not be affected, and the depth would be reduced from a usual 4.5 feet to about 4 feet. Figure 24 shows, pictorially, the effect on streamflow if 30 mgd were taken from the creek during low flow. A diversion of this amount is a negligible part of the total flow into Deer Point Lake and would have no adverse effect on this water supply.
   Some of the diverted water would be returned to Econfina Creek by an increase in the flow of artesian springs. The higher spring flow would result from an increase in the piezometric slope caused by recharge to the Floridan aquifer from the lakes.

                             SPRINGS
    The artesian springs along Econfina Creek are located downstream from a point just east of Porter Lake. Spring flow to the creek increases downstream to a maximum near the Washington-Bay County line. Below Gainer Springs it diminishes and there is little, if any, spring flow to the creek below the gaging station near Bennett, as shown on the flow chart in figure 25.
    Spring water flows into Econfina Creek directly through the stream bed, from the base of rock bluffs, and from short spring runs about a quarter of a mile in length. The spring water emanates from the Floridan aquifer where Econfina Creek has breached the overlying, confining clay layer. Figure 22 illustrates the hydrologic relationship of the aquifer with the creek. Figure 13 shows the pattern. of flow towards the springs.