FLORIDA GEOLOGICAL. SURVEY


about equal to the annual rainfall on the drainage area of 129 square miles. Streaniflow records have been collected since 1936 at Porter Bridge near Bennett at a point where the drainage area is 122 square miles.
   The average flow of Econfina Creek from the upper half of the basin is 90 mgd, only one-fourth of the flow from the entire basin. Upstream from Tenmile Creek (fig. 1) the flow during dry periods is seepage from the shallow sands. Downstream from Tenmile Creek artesian springs contribute most of the dry-weather flow. The minimum flow from the entire drainage area of Econfina Creek is about 210 mg-d, or seven times the minimum flow of about 30 mgd from the upper half of the drainage area.
   Floods occur on Econfina Creek almost every year. The creek has overflowed its banks at least once each year in all but six of the last 28 years. The longest period that it has stayed within its banks is the 3-year period August 1950 to September 1953.
   Bear Creek is the second largest creek in the basin and has an average flow of 226 mgd. It drains almost entirely from the sand hills and flow is supported by seepage from these sands.
   The average total surface flow into the bays was estimated as 960 mgd. Econfina Creek and Bear Creek contribute 581 mgd of this flow. The remainder of the average flow (379 mgd) comes from the smaller streams in the basin. The larger streams are listed in table 1.


                           STORAGE
   Rainfall, although it varies, supplies an adequate amount of water to the basin. Water held in storage in lakes and aquifers eliminates frequent shortages which would result from the inconsistent rainfall.

                             LAKES
   There are about 80 named lakes in the basin. Most of the lakes are in southeastern Washington County. Deer Point Lake (see p. 87), a fresh-water reservoir covering 4,700 acres in Bay County, is the largest. Porter Lake in Washington County has a surface area of 930 acres and is the largest natural lake.
   The natural lakes have not been developed for water use to any great extent although they offer considerable potential as recreational facilities. Wide fluctuations in most lake levels, caused by seepage losses to the ground and variations in rainfall, discourage their development. The Washington County Development Authority has pro-