PROBLEMS FROM DEVELOPMENT 45 



ground; in the Grand Prairie area there is abundant precipita- 

 tion, but the Drift Prairie and High Plains are semiarid. One 

 feature in common, however, is the existence of impermeable 

 clayey material that prevents significant recharge. Such con- 

 ditions, though rare, can occur in humid as well as arid regions. 



Southern High Plains of Texas and New Mexico. 7 By 

 prodigious development in the past four years, the Southern 

 High Plains now ranks fourth in the United States in usage 

 of water from wells. In 1949 the pumpage was of the order 

 of 1,250,000 acre-feet from 12,000 irrigation wells — about 

 the same amount of water as is normally used by New York 

 City's 8 million inhabitants. By contrast the pumpage in 

 1935 was about 50,000 acre-feet, about half in Texas and 

 half in New Mexico. In the ensuing 14 years the pumping 

 in New Mexico has increased fivefold, but the great expan- 

 sion — to more than 40 times the rate of pumping in 1935 — 

 has been in Texas. This expansion has occurred chiefly in 

 a 6,700-square-mile area, embracing parts of 17 counties. 



The Southern High Plains receives about 20 inches of 

 precipitation a year on the average, of which 70 per cent 

 falls during the growing season. In exceptional years, as in 

 1941, rainfall is sufficient and properly distributed for grow- 

 ing crops without irrigation. In most years some irrigation 

 is beneficial as a supplement to the summer rains, but the 

 average annual requirement is only about 1 acre-foot per 

 acre in the Texas area, far less than is required in most ir- 

 rigated areas of the arid Southwest. More than 99 per cent 

 of the annual precipitation is returned to the atmosphere 

 from the soil zone, which is seldom moist to any great 

 depth. Even during periods of prolonged storms and exces- 



t References: Barnes. J. R. ( et al, "Geology and Ground Water in the Irri- 

 gated Region of the Southern High Plains of Texas," Texas 

 Board of Water Engineers, Progress rept. 7, 1949, 51 pp. 

 Frye, J. C. and V. C. Fishel, "Ground Water in Southwestern 



Kansas," State Geol. Survey Kans., 1949, 24 pp. 

 "Oklahoma Waters," Oklahoma Planning and Resources Board, 

 Photolith rept., pp. 118-120, 1945. 



