INCREASING REQUIREMENTS 221 



rigated acreage and pumping from wells have increased 

 phenomenally since World War II and where the cost of 

 pumping has risen as the water level in wells has declined. 

 Several of these are "marginal" areas as far as economic feasi- 

 bility of pumping is concerned and are probably sustained 

 chiefly by the present price-support structure for farm crops. 

 The rate of pumping can be expected to level off and prob- 

 ably decline when the crops must compete with those from 

 regions more favored in water resources. 



The irrigation use that benefits the farmer is chiefly a con- 

 sumptive use, although in arid regions downward percolation 

 of excess water also serves a useful purpose in preventing ac- 

 cumulation of saline residues in the soil. Most of the economies 

 that can be effected by more efficient irrigation practices will 

 probably reduce the nonconsumptive use (downward perco- 

 lation) rather than the consumptive use. Sprinkler irrigation 

 is especially effective in reducing the nonconsumptive use, but 

 this economy can backfire in a ground-water basin where 

 water is fully appropriated and where equilibrium has been 

 established on the basis of substantial downward percolation 

 from irrigation: if any appreciable number of appropriators 

 decide to irrigate new acreage with the water they have 

 "saved," the basin may soon show signs of overdevelopment. 



There is a prospect of greatly increased demands for water 

 by industry. If the dominant uses continue to be cooling and 

 washing, the increased demand will be chiefly for noncon- 

 sumptive purposes. Air conditioning is already making large 

 demands on existing water-supply systems, and that industry 

 bids fair to expand tremendously in the future. The water 

 used is practically all nonconsumptive, but the quantities of 

 water circulated can seriously overtax existing municipal sup- 

 ply and sewage systems. According to estimates made in 1936, 4 

 a maximum water requirement of 300 million gallons a day 

 was forecast for the Loop district in Chicago when air- 

 conditioning installations reach the saturation point — six 



4 Gayton, L. D., Air Conditioning as a Problem of Water Distribution and 

 Disposal, Jour. Am. Water Works Assoc, vol. 29, no. 6, pp. 808-821, 1937. 



