Prior to the mid 1980s, Scottsdale relied almost entirely on groundwater for its water supply. Today, about 90 percent of our drinking water comes from two surface water sources: the Central Arizona Project and the Salt River Project.
Central Arizona Project
About two-thirds of Scottsdale’s water supply comes from the Central Arizona Project (CAP) – a 336-mile-long system of aqueducts, tunnels, pumping plants and pipelines designed to bring about 1.5 million acre-feet of Colorado River water per year to water users in Pima, Pinal and Maricopa counties. CAP carries water from Lake Havasu near Parker to the southern boundary of the San Xavier Indian Reservation southwest of Tucson.
Scottsdale began using CAP water in 1987 and our CAP allocation for 2015 is approximately 81,000 acre-feet. CAP water is treated at the 70 million gallon a day CAP Water Treatment Plant, located at the Water Campus in north Scottsdale.
Salt River Project
In 1903, Arizona settlers formed the Salt River Valley Water Users Association (Salt River Project) and pledged more than 200,000 acres of their land as collateral for a government loan to build a water storage and delivery system. They used this loan to build Roosevelt dam. As Phoenix grew, SRP added three more dams on the Salt River and two dams on the Verde River.
Scottsdale's SRP supplies are delivered through the Arizona Canal to the city’s Chaparral Water Treatment Plant, located near the intersection of McDonald Drive and Hayden Road. The 30 million gallon a day capacity plant has been in operation since the spring of 2006. The total SRP supply available to Scottsdale in normal supply years is 16,894 acre feet per year.
Unlike other sources of supply, which can be used anywhere within the Scottsdale service area, SRP supplies are available only to certain parts of the city, referred to as "on-project" lands. Scottsdale’s on-project land is south of the Arizona Canal.
Groundwater and Sustainability
Groundwater wells serve as back-up to our surface water supplies. To make sure the groundwater is there when we need it, we pump only as much groundwater as we actually need. We also recharge Central Arizona Project (CAP) and advanced treated recycled water into the aquifer to bank for future use.
Commitment to Safe Yield
In 1980, the State of Arizona adopted the Groundwater Management Act (GMA) to control the groundwater overdraft that was occurring in some portions of the state, mainly the urban areas of Phoenix, Tucson and Prescott and the farming areas in Pinal County. The GMA established a goal of safe yield by 2025 for the Phoenix Active Management Area (AMA), which includes Scottsdale. Safe yield means balancing the amount of artificial and natural water recharged into the aquifer with the amount of groundwater pumped out of the aquifer (in other words, putting in as much as you’re taking out).
Prior to the mid 1980s, Scottsdale was 100 percent dependent upon groundwater for our water needs. Today, Scottsdale receives less than 10 percent of its water supply from groundwater sources. By increasing artificial recharge and decreasing groundwater pumping, Scottsdale has been achieving safe yield since 2006, nearly 20 years before required by the GMA.
By maintaining safe yield, Scottsdale demonstrates responsible stewardship of its groundwater resources while continuing to provide a reliable and sustainable water supply for future generations.
100-Year Assured Water Supply
The Groundwater Management Act requires that anyone who wants to sell or lease subdivided land anywhere in an AMA must show the Arizona Department of Water Resources that an assured water supply exists to meet the water needs of the development for the next 100 years. Scottsdale has proved that it has an assured water supply for its entire water service area. This means that any subdivision that gets water from Scottsdale will not have to obtain its own independent certificate of assured water supply.
Scottsdale Water operates one of the most extensive aquifer recharge program s in the country. Established in the late 1990s, the program promotes aquifer sustainability, ensuring our aquifer remains viable and available for use during surface water shortages and to meet peak demands.
Scottsdale Water recharges the aquifer at the Water Campus by putting highly treated recycled water and filtered CAP water into the ground through vadose zone recharge wells.
Scottsdale also recharges treated CAP water through specially designed dual use groundwater production wells (ASR wells). ASR wells can pump water out of the ground just like regular wells, but they can also put water back into the ground to help replenish the groundwater aquifer.
ASR wells allow Scottsdale to increase use of our CAP allocation throughout the year. In the summer, all of the CAP water treated at Scottsdale’s CAP treatment plant is used directly by Scottsdale customers. When demand is lower in the winter, some of the water treated at the CAP plant is recharged through ASR wells to replenish the groundwater table for later recovery and use.
Recharged more than 29,000 acre-feet or 9.51 billion gallons of water into the aquifer in 2014.
Drought and Supply Planning
The United States Western Region, including Arizona and the Phoenix metropolitan area, has been in a drought – a prolonged period of significantly below-average precipitation – for more than a decade.
Scottsdale, however, has been preparing for drought conditions for decades. We have been proactive in the planning of long-term, sustainable water supplies and have secured a diverse and resilient water supply portfolio that reduces the community’s vulnerability to the risks associated with potential future supply reductions.
Scottsdale’s water resources Master Plan details a strategic long-term direction emphasizing the increased use of renewable and surface water supplies while reducing groundwater pumping. The city has quadrupled its original Central Arizona Project (CAP) supply by purchasing available CAP supplies over the last two decades. Additionally, Scottsdale was the first city in the Valley to institute a dedicated Water Resources Acquisition fee used to purchase CAP water. Every new development in Scottsdale since 1987 has paid this fee.
Scottsdale Water also maintains one of the most advanced water recycling programs in the country.
Drought Management Plan
In April 2021, Scottsdale's City Council approved the updated Drought Management Plan, which details the city's responses to drought conditions if water deliveries to treatment plants are reduced or curtailed, resulting in a reduction of water deliveries to customers.
There are four drought stages in this plan with each stage representing a progressively severe condition and including increasingly stringent water conservation measures. These measures aim to reduce water use progressively with each stage.
Scottsdale recognizes that every drop of water is precious in the desert. In addition to assuring the stability of the community’s long-term water supply, we are also leading stewards in minimizing our water use.
- Park staff keeps Scottsdale’s parks green and water lean by maintaining a water budget and using water-saving techniques to reach goals.
- Scottsdale’s water features use recirculating pumps to recycle water and only run during business hours or to minimize water loss through evaporation.
- Scottsdale employs a certified Green Plumber (trained in water-efficient technologies) and has retrofitted its buildings with water-efficient plumbing devices.