Watershed

Sources

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Map of watershed in Arizona

Phoenix has three sources of water – surface water (rivers and lakes), groundwater pumped from wells, and reclaimed water, used for agriculture, and industrial cooling and landscaping. Our supplies are rarely in a location where most of the population can see them.

On this website you can learn about Phoenix’s sources of water, where it is treated, and how we plan for our customer’s needs.

Map showing an overview of the water sources used in Arizona.
  • The Colorado River

    • Colorado River

      Up to 693 miles

    The Colorado River typically accounts for nearly half of the City’s water supply. It winds over 1,400 miles from Colorado to the Gulf of California in Mexico. The watershed covers approximately 244,000 square miles, including parts of Wyoming, Colorado, Utah, New Mexico, Nevada, California, Arizona and Mexico. The Colorado River has to meet the water needs for parts of these states and Mexico.

    Melting winter snows from the mountains of Colorado, Utah and Wyoming provide more than 85% of the river’s water. The amount of melting snow varies considerably year to year and prolonged drought - sometimes lasting decades – is not unusual. A rainy winter in Phoenix does not mean snow will fall where needed to melt into the Colorado River and fill Lakes Powell and Mead.

  • Salt and Verde Rivers

    • Verde River

      Up to 128 miles
    • Salt River

      Up to 165 miles
    Photo of the Salt River in January

    The Salt and Verde Rivers are another major water resource for Phoenix residents. More than a century ago, farmers in the Salt River Valley sought help from the federal government, which built a series of dams and reservoirs along the Salt and Verde Rivers for providing and storing water for their use. These lands are now what we know as the Salt River Project, which now mostly provides water for urban uses.

    The rivers are fed by winter snows above the Mogollon Rim northeast of Phoenix. Winter weather systems, fires, and summer monsoons can all have an impact on the quantity and quality of this water resource.

  • Hoover Dam and Lake Mead

    • Hoover Dam

      About 234 miles
    • Lake Mead

      About 234 miles

    Hoover Dam is an engineering wonder that has made it possible to harness the Colorado River and provide water and energy to Arizona, Nevada, and southern California. Completed in 1935, the dam created Lake Mead, the largest man–made reservoir in the United States. The lake can store up to 9,299 trillion gallons of water or the entire average flow of the river for two years.

    In 2010, after an eleven year drought, the lake’s level dropped to its lowest level since filled 75 years ago. However, heavy snowfall in the Rockies during winter 2011 provided enough water to raise the lake more than 13 feet.

  • Lake Powell and Glen Canyon Dam

    • Lake Powell

      About 244 miles
    • Glen Canyon Dam

      About 244 miles
    Photo of Lake Powell

    Glen Canyon Dam creates scenic Lake Powell, the second largest reservoir on the Colorado River with capacity to hold 8,798 trillion gallons of water. The completion of the dam in 1966 nearly doubled storage capacity of Colorado River water. The combined capacity of Lakes Mead and Powell helps prepare for dry years. However, when the levels of the lakes drop due to a long drought, it can take a long time to refill them.

    The primary purpose of the dam is to generate electrical power to areas of western United States. The generation and sale of 4.5 billion kilowatt hours of electricity help pay for the original cost of the dam and to maintain the system.

  • Roosevelt Lake and Dam

    • Roosevelt Lake & Dam

      About 56 miles
    Photo of Roosevelt Dam

    Fifty-six miles northeast of Phoenix is Roosevelt Dam, the first federal project created to supply water for the Valley. The dam was completed in 1911 and created Roosevelt Lake. The lake can store more than 539 trillion gallons of water and is the largest lake on the Salt River system. There are also a series of small lakes closer to the Valley well known for recreation.

    The dam and lake are very important for managing the Salt River and for providing a consistent supply of water to the Valley. However, compared to the Colorado River System, the ability to store water on the Salt and Verde Rivers is small. It is not unusual to find water flowing in the Salt River through Phoenix during wet winters when the lakes of the Salt and Verde Rivers are full. In 1996, the dam was raised to improve flood control and increase storage.

  • Central Arizona Project

    • CAP Canal

      Starts 136 miles
    Photo of the Central Arizona Project canal

    In 1963, the Supreme Court settled a long running dispute between Arizona and California. The Court decided Arizona has a lower priority to Colorado River water than California. If there is a severe shortage, Arizona’s supply from the Colorado River may be reduced. However, the Court ruling allowed for construction of the Central Arizona Project, which was authorized in 1968, to bring Colorado River Water to central and southern Arizona for the first time.

    Construction of the Central Arizona Project began in 1973. The canal was completed to Phoenix in 1986 and to Tucson in 1992. The canal is designed to carry 3,000 cubic feet of water per second. Because the Central Arizona Project transports Colorado River water uphill for its entire length, it is the largest power user in Arizona.

Wet and Dry Cycle

Researchers at the University of Arizona have studied tree ring records to understand how wet and dry weather cycles impact the Colorado, Salt and Verde Rivers during the last 800 years. Generally, the wider the ring, the more the tree grew because it was a wetter year. Likewise, narrower rings indicate less growth and drier conditions. This study and others like it indicate that there can be lengthy wet and dry periods on the rivers. Many times, these periods happen on all three rivers simultaneously.

While the City has rights to extensive supplies and has long-range plans to ensure an adequate supply of water for residents and business, it’s possible there will be a shortage if another prolonged dry period occurs on the rivers. Were a shortage to occur in the future, residents and businesses would be given ample information and preparation time.

Photo of a stump from above.
  1. 1200 – Now

    During the last several centuries in the Southwest, there have been periods of heavy rainfall and snow causing severe flooding. There have also been long periods of drought. Studies at the University of Arizona’s Laboratory of Tree Ring Research have helped develop an understanding of the climate and its effect on communities in our desert climate.

  2. 1200 – 1300

    Around 1275, studies show that there was a ‘great drought’ in the Southwest. Droughts can cause disease and pest infestation to trees and wildlife. An example is the recent infestation of the Pine Bark Beetle in our forests which has killed more than 50% of trees in some areas.

  3. 1400 – 1500

    The Hohokam community is believed to have been as large as 24,000 to 50,000 people, a population that would need a constant supply of water for crops and home in our arid desert. Sometime around 1450 AD, the people abandoned the greater Phoenix area. Tree ring studies show that there was a great flood at that time and may have destroyed the canal system that made living in the desert possible.

  4. 1500 – 1600

    Researchers have discovered through tree ring studies that the much of the southwestern United States and Mexico experienced a severe drought in the late 1500s, unlike any dating back as far as 1200 AD. Droughts of this type impact agriculture, natural resources, and may have even led to war to gain water sources to sustain a community in Mexico.

  5. 1900 – 1922

    The Colorado River Compact determined states water usage based on average river flows at Lee’s Ferry for a period prior to 1922. It has since been established through tree ring research that the river was over-allocated by about 3-million acre feet due to higher than average flows during that time.

  6. 1950 – 1957

    A severe drought for the Southwestern U.S. began in 1950 and lasted until 1957. This drought was characterized by both high temperatures and low rainfall. The impact on agriculture was especially harsh for cattle ranching and reduced crop yields by as much as 50%.

Water Treatment Plants

Photo of a water treatment plant

Phoenix has five water treatment plants delivering a safe and reliable water supply to your home. The Central Arizona Project delivers Colorado River water to the Union Hills and Lake Pleasant Water Treatment Plants are in north Phoenix. Three plants in central Phoenix treat Salt River Project water for customers ‘on project’. During plant maintenance or drought, Central Arizona Project water can be moved to all plants for delivery.

More than 6,000 miles of interconnected water pipes delivers about 264 million gallons of water daily to Phoenix customers. Deliveries are adjusted monthly to meet customer demands and vary depending on a variety of issues including weather, tourism, and other consumer needs.

Waste Water Treatment Plants

Photo of a waste water treatment plant

Wastewater is collected from Phoenix homes and businesses through more than 4,600 miles of pipe and sent to the City’s three wastewater treatment plants. Once treated, most of the reclaimed water is reused for cooling at Palo Verde Nuclear Generating Station, irrigating farmland, irrigating turf, and at the Tres Rios wetlands. Using reclaimed water at these locations preserves our drinking water supply.

Inside your house

When you look at all of the ways we use water in our homes, the average Phoenix resident uses more than 100 gallons a day for cooking, bathing, laundry, watering the yard and many other ways. You can turn on the faucet and the water is ready for you as part of your lifestyle.

Here you can learn more about water technologies and how you can use them more efficiently every day.

Cutaway illustration of a two-story house revealing all of its rooms.
  1. Toilet

    Think before you flush

    Installing a high-efficiency toilet can save you $$$ and up to 10,000 gallons of water per year.

  2. Shower with working shower head

    Know when 1 head is better than 2

    Don’t be tempted by multiple shower heads – 1 is better than 2. (Look for a WaterSense label.)

  3. Faucet

    Get a new look and save water

    It’s easy to enhance your décor and save water: replace old faucets and aerators with new, low flow ones.

  4. A wrench next to a leaking pipe

    Get a new look and save water

    It’s easy to enhance your décor and save water: replace old faucets and aerators with new, low flow ones.

  5. A plate with a fork and knife

    Plan 10 free days a year

    Stop washing dishes before you use the dishwasher. You can save enough time for a 10-day vacation.

  6. Water coming out of a shower head

    Make it hot

    Avoid running and pre-heating water before you shower. Install an “on-demand” hot water system.

  7. A clothes washing machine

    Commit to greater savings

    High-efficiency washing machines paired with full loads use about half the water of less efficient models.

Outside your house

Illustration of the yard of a house.
  1. A broom sweeping dirt

    Take simple steps

    Instead of a hose, use a boom to clean patios, paths and driveways. Use a shut-off nozzle with your hose.

  2. A cactus

    Choose plants that thrive

    For a wise investment, use Arizona-native and low-water-use plants and water them properly.

  3. Some flowers on a pile of dirt

    Dress up and save

    Top dressing planting beds with decorative mulches reduces water evaporation and cools soils.

  4. A toolbox

    Keep chemicals in check

    Fine tuning your pool chemistry once or twice a week will save you from draining your pool too often.

  5. A tree

    Beat the heat

    Fight the “urban heat island effect” by shading your yard with Sonoran-native shade trees.

  6. A sprinkler sprinkling water

    Drip for savings

    Consider high-efficiency drip irrigation in your planting beds to reduce evaporation, and use water wisely.

  7. A sprinkler sprinkling water

    Zone like a pro

    Plan your sprinkler system so that you don’t overspray on patios, paths, driveways and other non-grass areas.

  8. A cactus

    Live more, limit lawn

    Reduce yard maintenance and watering by limiting grass and using patios and desert plants in your yard.

Inside your business

Showing your employees and customers your business’ commitment to sustainability will enhance your company image, and help improve your bottom line. By investing time learning about new water using technologies, educating your employees about water efficiency, and passing reliable information to customers, you will develop good will for your company.

Cutaway illustration of a commercial building revealing all of its rooms.
  1. Symbol of recycling with a drop of water in its center

    Stand up for savings

    Assigning a water steward in your business helps communicate your commitment to being a “green” business owner.

  2. A shower head spraying water

    Cut the spray

    Check for the WaterSense label on showerheads, commercial spray nozzles, and other water using technologies.

  3. Ice

    Crack the ice

    Air-cooled ice makers can save 1,300 gallons of water daily over water-cooled models. Energy cost increases = insignificant.

  4. A hanging lamp

    Lower overhead

    High-efficiency fixtures can substantially reduce your operating costs. Consider WaterSense labeled fixtures when remodeling.

  5. A clothes washing machine

    Fight waste, install a front loader

    New, high efficiency washing machines save water and energy costs. Look for programmable models that respond to load size.

  6. A couple documents with a drop of water on them

    Keep informed

    Keep informed of new water-saving technologies in your industry and cut your costs by reducing waste.

  7. Air conditioner

    Keep it cool

    Upgrade antiquated, once-through cooling systems to air-cooled technology may save you water and energy costs.

Outside your business

The outside of a commercial building including grass, a path, various plants, and some tables
  1. Desert plants on a mound of dirt

    Send a message

    Your landscape can demonstrate that you care about the environment. Create a landscape that is desert friendly and water saving.

  2. A cactus

    Tame outdoor maintenance

    Native Sonoran or low-water-use plants offer a maintenance-free alternative to high water-use grass and exotic plants.

  3. A couple chairs under an umbrella

    Shade your investment

    Opt for shade trees, umbrellas and patio covers to keep customers cool instead of high water using misters.

  4. A wrench next to a leaking pipe

    Be a leak detective

    Even the smallest leak can be damaging to your property and wastes significant amounts of water.

  5. An irrigation system

    Water for efficiency

    Plan to upgrade irrigation systems to increase efficiency. New technologies can offer quick returns on investment.

  6. An irrigation system

    Get in the zone

    Implement “hydrozoning” principles that combine water-saving systems: “grass-only” zones, high-efficiency heads and drip irrigation.

  7. A broom sweeping dirt

    Clean it dry

    Find ways waterless ways to clean patios, sideways, and driveways. Limit use of blowers to reduce air pollution.

  8. Symbol of recycling with a drop of water in its center

    Keep it wet

    Good business means protecting your assets. Organic wetting agents and decorative mulches help protect your landscape.