222 CONSERVATION OF GROUND WATER 



times the peak rate in 1929 before air conditioning. This esti- 

 mate assumed no water-conservation devices. The use of 

 conservation devices such as condensers or cooling towers 

 generally cuts down the water use by 90 to 95 per cent, but 

 most of the water is then used consumptively. 



Heat-exchange systems, which use water for year-round air 

 conditioning, are certain to become popular in areas where 

 electric power is cheap enough. Although water is used the 

 year round for heat exchange, the depletion of water resources 

 can be far less than for air conditioning during the summer 

 only. As an example, the water for the heat-exchange system 

 in the 12-story Equitable Building in Portland, Ore., comes 

 from two different aquifers with a temperature differential of 

 6° F. 5 In winter the system takes the warmer water, extracts 

 the heat, and returns the water to the colder aquifer. In sum- 

 mer the cycle is reversed. Thus one aquifer stores the heat of 

 summer for use in winter, the other stores the cold of winter 

 for use in summer, and there is practically no net loss of water 

 from either. 



Several industries of the future may be expected to make 

 large additional demands on water resources. For example, 

 the hydrogenation of coal is an extravagant user of water: on 

 the basis of a tentative estimate of 6 million gallons per day 

 for 10,000 barrels of oil from coal, it would take more than 

 3 billion gallons a day for synthetic manufacture of oil equiva- 

 lent to the United States production in 1949. This is nearly 

 three times the quantity of water used by New York City's 

 8 million people. 



An important question is where may these increased de- 

 mands be expected to occur — because the answer will show 

 whether the present problems in the arid regions or in the 

 centers of population and industry are to be aggravated. Un- 

 doubtedly there will be some areas where present conditions 



s Kroeker, J. D., and R. C. Chewning, A Heat Pump in an Office Building, 

 Heating, Piping, Air Conditioning, vol. 20, no. 3, pp. 121-128, 1948; Kroeker, 

 J. D., R. C. Chewning, and C. H. Graham, Heat Pump Results in Equitable 

 Building, Heating, Piping, Air Conditioning, vol. 21, no. 7, pp. 115-121, 1949. 



