Urban Ecology

Where does our water come from?

by Conrad J. Storad

The Phoenix area is a desert with limited amounts of water. Yet the population keeps growing, using more and more water every year. Where does this water come from?

Local rivers
The Salt and Verde rivers have been dammed in several places to collect water in reservoirs for use by people.

Groundwater sources
Water that exists underground can be pumped up through wells. Unfortunately, people are using more groundwater than Nature can replenish.

Effluent
Effluent is basically recycled wastewater. The water is treated but not clean enough for drinking or bathing. However, it can be used for things like watering golf courses and cooling power plants.

Central Arizona Project
Since 1985, water has been carried 336 miles through CAP canals from the Colorado River to the Phoenix area to supplement local water supplies.

How much water are we using?
In 1998, the Phoenix Active Management Area used 2.3 million acre-feet of water. An acre-foot is the amount of water required to cover an acre of land with one foot of water. It is about 325,851 gallons, enough to serve a family of four for a year. Most of the water (44 percent) was used for farming. Another 36 percent went to city water supplies. Industry used 7 percent. 13 percent went to other uses.

Did you know?
It takes 8 gallons of water to grow one medium tomato, 36 gallons to produce a serving (2 ounces) of pasta, and 1,232 gallons to produce one 8-ounce steak.