WATER RESOURCES
 OF
 ESCAMBIA AND SANTA ROSA
 COUNTIES, FLORIDA

 By
 Rufus H. Musgrove, Jack T. Barraclough,
 and Rodney G. Grantham


 ABSTRACT
 Escambia and Santa Rosa counties, the westernmost counties in
Florida, have an abundant supply of both ground and surface water of
excellent quality. A 4-year study was made to determine the quantity
and quality of the water and the possible effect of municipal and indus-
trial expansion on the water.
 Over 8.5 bgd (billion gallons per day) of fresh water flow into the
200 square miles of estuarine bays from four major rivers. Only about 5
per cent of this water is used. The Escambia River, the fifth largest in the
state, has an average flow of over 4.5 bgd. Many smaller streams within
the area produce large quantities of water.
 Most of the 87 mgd (million gallons per day) of water taken from
the ground comes from the sand-and-gravel aquifer. This aquifer extends
from the water table down to various depths ranging from 200 to 1,000
feet. In parts of this aquifer the water is confined under artesian pressure
by numerous layers of clay and hardpan. The sand-and-gravel aquifer
contains a large supply of exceptionally soft and unmineralized water.
 The Floridan aquifer, consisting of limestones which underlie the
sand-and-gravel aquifer, contains a large supply of harder, more mineral-
ized artesian water, and is virtually untapped.
 Recharge of the sand-and-gravel aquifer is by local rainfall. The
 Floridan aquifer is recharged by rain falling in southern Alabama, 10 to
 35 miles north of the area, and by downward leakage from the sand-and-
 gravel aquifer.
 Factors such as decline of the water table, salt-water encroachment,
 and contamination of surface and ground water can greatly affect the
 availability of water of good quality. Decline in the water table may be
 caused by below-normal rainfall or heavy pumping of closely spaced
 wells. Salt-water encroachment is likely to occur where heavy pumping