108 CONSERVATION OF GROUND WATER 



to the Gulf of Mexico. The principal recharge area is 10 

 to 50 miles north of the rice-growing area, where the per- 

 meable gravel and sand of the aquifer are at or near the sur- 

 face, but there is also some recharge along stream valleys 

 that have cut through the clay that covers the aquifer 

 throughout the rice area. Precipitation in the recharge area 

 is 55 to 60 inches a year, sufficient to replenish the ground- 

 water reservoir as fast as water moves southward toward the 

 pumped wells, and there has been no significant lowering 

 of the water table in the recharge area since pumping be- 

 gan. 



Pumping has created deep cones of depression in the 

 artesian-pressure surface near Lake Charles and under the 

 rice-growing areas to the east. That surface was below sea 

 level under an area of about 4,000 square miles in Septem- 

 ber 1949, and more than 30 feet below sea level near Lake 

 Charles and under some of the rice-growing areas to the east. 

 In 1948, when the annual pumpage for all purposes was 

 about 700,000 acre-feet, water levels in wells went lower 

 than ever before; but these cones of depression have been 

 deepening progressively at an average rate of about half a 

 foot a year for at least the past 35 or 40 years because of 

 pumpage. After seasonal pumping ceases, water levels rise 

 in the center of each cone of depression while those on the 

 flanks continue to decline for several weeks, indicating that 

 the pumped water is replaced by inflow from all directions. 

 Some of the water may also be replaced by upward move- 

 ment, as suggested by the higher salinity of water from wells 

 in the centers of the cones of depression. There may be some 

 contamination of the aquifer from streams, which are salty 

 in their lower courses during the late summer of dry years. 



The ground-water problem in southwestern Louisiana 

 appears to be due principally to the inability of the aquifer 

 to transmit water from the recharge area in quantities suf- 

 ficient to meet the demand of existing wells. Pumping has 

 increased the hydraulic gradient from the recharge areas, 

 and therefore the rate of movement of water toward the 



