Saving Water: Part 2

The fate of the Colorado Rivers implies the second good reason for conserving water. Agriculture, industry, urbanization, and a growing population are placing increasing demands on water supplies. As pressure on the water supply increases, there will be regional water shortages.

Thirty dams tame the Colorado River and its tributaries, and two massive reservoirs (Lake Mead and Lake Powell) store its water. Aqueducts and irrigation canals siphon off its water for use in seven western states and northern Mexico. Los Angeles, Denver, and hundreds of other cities could not exist as they are today without the water the Colorado provides, and the fruits and vegetables raised in the Central and Imperial Valleys would die.

Legally, all the water in the Colorado Rive is spoken for. California receives 4.4 million acre-feet per year, Arizona 2.8 million acre-feet, and so on. (One acre-foot is the amount of water that would cover an acre of ground with a foot of water – about 326,000 gallons.) indeed, yearly allotments now stand at 16.5 million acre-feet, in spite of the fact that the Colorado rarely carries more than 14 million acre-feet! Shortages have not occurred yet simply because not all the states are using the full share to which they are entitled. But demands are expected to increase to that point in the very near future, perhaps by the end of this decade.

Another area where the demand for water is beginning to exceed the supply is the High Plains region, which stretches from South Dakota to Texas. Agriculture there depends on drawing irrigation water from a vast underground formation called the Ogallala aquifer. (An aquifer is a layer of water-bearing, porous rock lying between impermeable layers.) The Ogallala aquifer is the country’s largest underground water supply, spreading under twenty million acres in eight states. It supports nearly half the country’s cattle industry, a fourth of its cotton crop, and a great deal of its corn and wheat. But the 150,000 well s that now puncture the aquifer cause the water table to fall from 2 to 5 feet (0.6 to 1.5 m) each year – a rate that is far greater than the rate at which the aquifer can be replenished by nature. Hydrologists expect that as much as 40% of the irrigated acreage will be lost in the next twenty year, causing economic hardship in the region and food shortages in the country.