REPORT OF INVESTIGATIONS No. 40


a natural flow of 110 gpm. The artesian pressure head was 51 feet above
the land surface and about 56 feet above sea level. The chloride content
of the water is 87 ppm and the dissolved solids is 380 ppm. Water from
this well is soft as the hardness is only 16 ppm.

 WATER PROBLEMS
 Problems concerning water resources can be divided into those re-
sulting from natural causes, those arising from man's use of water, and
those resulting from a combination of both.

 PROBLEMS FROM NATURAL CAUSES
 Water problems arising from natural causes are usually associated
with too little or too much rainfall, the areal geology, or by the mineral
content of the water. Deficient rainfall causes the water level in wells
to decline, runoff from streams to decrease, and pond levels to be low-
ered. Excessive rainfall may cause flooding of lands that are poorly
drained and lands adjacent to streams. Problems of water development
occur in areas where the geology is such that aquifers are limited. The
mineral content of water may limit the usefulness of the water.

 PERIODS OF LOW RAINFALL
 Decline of water levels.-The relation of ground-water levels to rain-
 fall is shown by the hydrographs of wells in this area. During periods of
 low rainfall, the water level declines. This may result in drying up of
 shallow wells and salt-water encroachment. In well 031-716-1 at Ensley,
 the water level dropped more than 9% feet in 1950 and again in 1954
 (fig. 34). These declines were due to a reduction in recharge brought
 about by below-normal rainfall.
 The levels of ponds drop during low rainfall periods and some ponds
 go dry. Streamflow decreases during the dry periods.
 Salt-water encroachment.-Low ground-water levels and below-normal
 streamflow, brought about by lack of rain, allow salt-water encroachment
 into surface and ground-water supplies. During periods of low rainfall
 the streamflow decreases and the salt-water front moves upstream.
 Lowered ground-water levels may allow upward or lateral salt-water
 encroachment. Upward encroachment is possible where the lower aqui-
 fer has a higher head than that in the upper aquifer. Lateral encroach-
 ment into ground water from surface bodies of salt water is possible
 where ground-water has a lower level than the surface water level. The