How We Get Water in the Desert

Today, we’re going to talk about Phoenix area water, where it comes from, how it's treated, the water quality and disbursement.

The water we get in the Phoenix area is derived mostly from surface water: some of our water comes from lakes and wells. We have to be careful of the amount of groundwater we use, since a groundwater overdraft will adversely affect the natural plant and animal populations with whom we share the water supply.

About half of our drinking water comes from the Colorado River. The river is created by melted snow from Colorado, Utah, and Wyoming. We share the Colorado River water with California, Nevada, Wyoming, Utah, Colorado and New Mexico. The portion of that water which we use comes to us through the CAP waterway to the Union Hills and Lake Pleasant Water Treatment Plants in north Phoenix. (There are also three water treatment plants in Central Arizona.)

 The Central Arizona Project, or CAP, brings us about half our water.

The Central Arizona Project, or CAP, brings us about half our water.

At the treatment plant, the first step is to run the water through screens to filter our leaves, twigs, and other bits that river water carries. Then the water is allowed to settle, so the biggest particles in the water turn to sediment and fall to the bottom of the pre-sedimentation tank. 

Next, a coagulant is added, which is a chemical that makes dirt particles stick together. These grouped particles become heavy enough that they also sink to the bottom of the tank. The water on top is sent through filters for further particle removal. 

In the last step, a tiny amount of chlorine is added to the water. Chlorine is a disinfectant, and will prevent microbial growth. Phoenix uses about one part per million of chlorine in the water leaving the treatment plant. The minimum federal standard is .2 parts per million. Also, a bit of fluoride is added to prevent tooth decay. 

 Tempe, Az

Tempe, Az

Throughout the process, the water is sampled and tested to insure the final product is safe and clean. Tap water is heavily regulated in most places; the Phoenix water quality surpasses all federal standards. While taste, odor and hardness do not affect the water quality, the city is sensitive on the subject of odor, since the water will sometimes carry an odor as a result of algae in the canals. This odor in no way affects the water quality.  

The water travels through seven thousand miles of main lines. The city has reservoirs and booster pumps to help move the water along, which totals to about 264 million gallons per day. Up to 4 parts per million of chlorine is added to the water in the distribution system. The average Phoenician uses about 100-130 gallons per day--mostly by flushing the toilet. 
Regulatory oversight for water quality is provided by the Environmental Protection Agency. The city water has to be in full compliance with EPA standards.

If you want to know more about the water quality, you can request a copy of the latest water quality report here.  

 We share the groundwater with plants and wildlife in Arizona.

We share the groundwater with plants and wildlife in Arizona.


If you want to learn more about the magnificent history of water in Arizona, the City of Phoenix Parks and Recreation department is offering a Park of Four Waters Tour at the  Pueblo Grande Museum February 24th March 31, and April 28.The Park of Four Waters tour will take you on a walk through undeveloped, natural desert to the ruins of prehistoric Hohokam canal systems and is free with museum admission.