ECONOMICS OF WATER SOURCES 325 
sewage treatment plant can, and many do, produce an effluent of 
better quality chemically and biologically than many public raw 
water supplies. In the United States about 125 municipal sewage 
plants utilize the effluent in agriculture. In addition, in at least 
a half-dozen cases, sewage effluent 1s used for industrial operations. 
Sewage effluent in general will cost about $10 per acre-foot, and 
one industrial plant is purchasing it for $6. However, municipal 
effHuents would in general supply only a fraction of the industrial 
requirement. Most industries make only one use of water, but in 
almost every case it would be possible to reduce water use greatly 
if a water shortage should develop. One plant in the Texas-Gulf 
Coast area reduced its requirement from 672,000 acre-feet per 
year to 44,000 by re-use; another from 224 acre-feet per year to 4. 
But there is no possibility that even combined municipal and in- 
dustrial reclaimed effluents can make more than a fractional 
contribution to irrigation supplies. 
Full and economic utilization of industrial waste waters will 
require further intensive research and development to provide 
suitable processes and a major educational campaign to persuade 
managements of the necessity. 
Generalized Economics of Arid Lands 
In making a few general remarks on the economics of arid lands, 
I take the liberty of the social scientist who, out of the necessities 
of the present stage of development of his science, must make 
broad generalizations from what the natural scientist would judge 
inadequate or faulty data. If I am in error, blame it on the natural 
scientist who dares to navigate these tricky waters, rather than on 
the economists who by much practice have learned to shoot the 
rapids without spilling a drop. 
Land Value Fluctuations 
Our economic systems and theories have been developed quite 
largely in lands enjoying adequate and regular rainfall. Under 
these conditions the value of the land, first for agricultural, then 
for industrial purposes, depends upon the inherent quality and 
productivity of the soil, on topography, and on the location rela- 
tive to the markets and raw materials. Land, therefore, even after 
