The Salt River Project has been delivering water, through 131 miles of canals, in Arizona for more than 100 years. Because we live in the desert, we typically do not get much rain, so we need to bring water into cities and towns from other parts of Arizona. When snowfall in the mountains north east of Phoenix melts, it forms small streams which come together to form the Salt and Verde rivers. This area is known as our watershed and covers approximately 13,000 square miles.
The amount of snow melt from our watershed varies from year to year…and since there is typically never a consistent supply of runoff, SRP constructed several dams along the Salt and Verde rivers, which created lakes, or reservoirs, to store the excess water. SRP controls the amount of water released from these reservoirs depending on whether we have a wet or dry winter. The reservoirs allow us to store the water for later use. When water is released from the storage reservoirs, it is then delivered to cities and towns through a series of canals.
The Central Arizona Project, or CAP, carries fresh water from the Colorado River to millions of people in central and Southern Arizona. CAP is a collaborative project that started back in 1922 with the federal government and the seven states that share Colorado River water. After decades of lobbying, a bill approving the construction of the CAP canal was passed by Congress in 1968.
Construction of the 335-mile-long project began in 1973 near Lake Havasu and was completed 20 years later just south of Tucson. Water in the CAP canal is lifted by 15 pumping plants almost 3,000 feet so it can flow through the system by gravity. Approximately 1.5 million acre feet or 489 Billion gallons of water is delivered every year to nearly 5 million people in cities like Phoenix, Tucson, Mesa, Glendale and Scottsdale.
Today, about one-third of CAP’s water is used by cities and industries. Farmers use about one-fourth of the water and one-tenth goes to Indian Communities. The rest of the water, about one-third, is pumped underground to use in the future.
Reservoirs
SRP built several reservoirs along both the Salt and Verde rivers to store water during the hot summer months and when we get below average snowfall. There are four reservoirs along the Salt River – Roosevelt, Apache, Canyon and Saguaro lakes; and two reservoirs along the Verde River – Horseshoe and Bartlett lakes.
The major reservoir of the CAP system is Lake Pleasant. Lake Pleasant is a 15-and-a-half square mile lake used to collect and store runoff from the Agua Fria River. CAP pumps water into the lake, filling it in the winter months and releasing water during the hot summer months.
Canals
CAP and SRP release water each day from their reservoirs into a series of canals that carry water to the treatment facilities. Canal water is either used to irrigate crops or treated for you to use in your home every day.
SRP also has hundreds of wells throughout Arizona that are an additional water supply. These wells can be more than one-thousand feet deep and can pump thousands of gallons of water every minute. These wells can supply up to one-third of the water we need each year.
Recharge
Both SRP and CAP store water underground for future use in a process called “recharge.” One method of recharge involves flooding an area with water and then letting it settle and drain down through the soil. Recharging helps replace underground water supplies which can then be pumped out and used at a later date.
As you can see, groundwater is an important natural resource, especially in areas that don’t have ample surface water sources, like much of Arizona.
