FLORIDA GEOLOGICAL SURVEY


content of the water. The mineral content of the water increases in the down gradient direction as more limestone is dissolved.
   In areas along Econfina Creek where the artesian pressure surface is above the land surface and the sand and clay are missing, springs have developed. Most of the flow of Econfina Creek is derived from these springs.
   In the southern hal of the basin, water may percolate downward from the water-table aquifer into the secondary artesian aquifer. The sandy clay material at the base of the water-table aquifer and at the top of the secondary artesian aquifer acts as a semi-confining layer which maintains the water in this aquifer under artesian conditions.
   The secondary artesian aquifer is composed of shell-hash with interlayered sand and limestone lenses. Water that moves into this aquifer from the water-table aquifer is slightly acid. This water dissolves the limestone and shell giving the water a calcium bicarbonate character.
   The water withdrawn from wells in the Floridan aquifer in the Panama City area entered the aquifer through the sinks in the northern part of the basin and in areas farther north where the limestone formations are at ground surface. By the time the water reaches Panama City the mineral concentration is five to six times that of water in the northern part of the basin. Part of the increase is caused by solution of the limestone and part is caused by mixing with older water in the rocks. The pressure gradient shows that the water is being flushed into the ocean at some point where the rocks are exposed to or hydraulically connected to the ocean bottom.

                    WATER AVAILABILITY
    The amount of water moving through each part of the hydrologic system must be known to properly evaluate a water resource. A knowledge of the environment is necessary to determine the chemical and physical properties of the water and to predict any changes in these properties that may result from withdrawal of water from the system-. Some of the parameters that affect the am ount and quality of water available are rainfall, strearnflow, water levels, rock composition, and the ability of aquifers to store and transmit water. These hydrologic features can be measured either by direct or indirect methods.
                             RAINFALL
    The Econfina, Creek basin receives an average rainfall of 58 inches per year, based on records collected at Panama City by the U. S.