Battling Drought: The Science of Water Management

Thanks to improved sewer systems, water-related diseases such as cholera and typhoid, once endemic throughout the world, have largely been conquered in the more industrial nations.

for drinking, hygiene and growing food for

Wheat, rice and cotton fiber respectively require about 1,500, 4,000 and 10,000 tons of water per ton of crop.

on average, each person on the earth needs a minimum of 1,000 cubic meters (m3) of water per year—equivalent

Even agriculture, man's principal consumer of water, takes little of the available supply. A billion acre-feet per year—less than 4 per cent of the total river flow—is used to irrigate 310 million acres of land, or about 1 per cent of the

Investments in the development of water resources have rarely exceeded 1 or 2 percent of the gross national product. In most countries they cannot be raised much above that level without causing hardship elsewhere in the economy. Capital is a resource in shorter supply than water, and the same strategies must be adopted for its conservation.

few industries account for some two-thirds of all the demand: they are metals, chemicals and petroleum refining, pulp and paper manufacturing and food processing.

Farmers can exploit the resulting composted organic matter as crop fertilizer.

irrigation about 1,000 tons of water must be "consumed," that is, changed by soil evaporation and plant transpiration from liquid to vapor.