REPORT OF INVESTIGATIONS No. 40


pears to be about the same throughout the basin. Based on records of
the eight gaging stations that are located throughout the basin, the av-
erage yield is about 21 inches per year, ranging from a low of 18.3 inches
to a high of 28.7 inches. The flows measured at these stations came from
drainage areas ranging in size from 75.3 to 3,817 square miles. The
average yield at the Century gaging station was 21.9 inches per year.

 MINERAL CONTENT
 The Escambia River passes through the outcrop area of the Floridan
aquifer in southern Alabama and dissolves minerals from these lime-
stones. The water of the Escambia River near Century has a mineral
content ranging from 47 to 101 ppm. This is generally considered to be
low mineralization, but compared to the waters of other streams in
Escambia-Santa Rosa counties, it is high. This mineralization is diluted
by the flow from the tributaries that empty into the Escambia River. A
semiannual station located on the Escambia River near Quintette shows
a maximum dissolved solids of 60 ppm. The extent of the salt water
wedge in the tidal reach of the river is dependent on the flow of the
river and the height of the tide in Pensacola Bay. During periods of high
tides and low flows, the salt water extends upstream just beyond the
Chemstrand plant (see figs. 23, 28).
 In the last 3 months of 1959 the flow in the Escambia River at Cen-
tury was high and as shown by the graph in figure 28 the chloride at the
Chemstrand plant was low. During the last 3 months of 1960 the situa-
tion was entirely different. The flow at Century was low and the chloride
at the Chemstrand plant was high. On November 22, 1960, the flow at
Century was 1,550 cfs (equaled or exceeded 90 percent of the time)
and the chloride at Chemstrand was 1,454 ppm. On August 22, 1961, a
chloride-profile run on the Escambia River (fig. 23) showed that the
salt front extended about 3& miles upstream. On this day the flow at
the Century gaging station was 2,380 cfs, (equaled or exceeded 70 per-
cent of the time).
 The tributaries of the Escambia River originate in highland regions,
the major recharge areas for the sand-and-gravel aquifer. Surface water
in these tributaries is very low in mineral content and generally is very
clear. However, color increases due to contact with organic material
during periods of high flow.
 Silica and color could be the two objectionable constituents in the
Escambia River. Silica ranges from 5 to 21 ppm and color ranges from
4 to 120 platinum-cobalt units. The quantity and quality of the waters of
the Escambia River basin make it a good potential source.