FLORIDA GEOLOGICAL SURVEY


water surface is lowered at any point within this cone is known as the
drawdown. The size, shape, and rate of growth of the cone of depression
depend on several factors: (1) the rate of pumping; (2) the duration of
pumping; (3) the water-transmitting and storage capacities of the aqui-
fer; (4) the increase in recharge resulting from the lowering of the
water surface; (5) the decrease in natural discharge from the aquifer
due to the lowering of that surface; and (6) the hydrologic boundaries
of the aquifer.
 A measure of the capacity of an aquifer to transmit water is the co-
efficient of transmissibility. This is the quantity of water in gpd (gallons
per day), that will move through a vertical section of the aquifer 1 foot
wide and extending the full saturated height of the aquifer, under a unit
hydraulic gradient, at the prevailing temperature of the water.
 The coefficient of storage is a measure of the capacity of an aquifer to
store water. It is defined as the volume of water released from or taken
into storage per unit surface area of the aquifer per unit change in the
component of head normal to that surface.
 The amount of water that may be stored in a rock or soil is limited by
the porosity of the material. The amount of water that a saturated rock
will yield when allowed to drain is somewhat less than the porosity
because some of the stored water will be held by capillarity.
 The amount of water stored by an aquifer also depends on whether
 the aquifer is artesian or nonartesian, for all aquifers serve as both con-
 duits and reservoirs. An artesian aquifer functions primarily as a conduit,
 transmitting water from places of recharge to places of discharge; how-
 ever, it is capable of storing water by expansion, or releasing water by
 compression. An artesian aquifer also stores water in the unconfined por-
 tion of the aquifer. A nonartesian aquifer functions primarily as a reser-
 voir and can store a much larger quantity of water for a given rise
 in the water level than can be stored in an artesian aquifer.
 The coefficient of transmissibility and coefficient of storage are gen-
 erallv determined by means of an aquifer test on wells. Although only a
 few aquifer tests have been made during the current investigation, many
 detailed tests have been made in parts of the area. The coefficients deter-
 mined by these tests are still applicable to the test areas and may be
 used for hydrologically similar areas.
 In the spring of 1940, Jacob and Cooper (1940, p. 33-49) made sev-
 eral aquifer tests on wells owned by the City of Pensacola, the U.S. Navy
 (at Corry Field), and Newport Industries. These wells were drilled
 about 240 feet into the sand-and-gravel aquifer, and the lower half was
 screened. The average coefficient of transmissibility, T, for 120 feet of