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The Valley’s water supply

Water is a precious resource here in Arizona, which is why we have a diverse water resource mix. This gives us some flexibility in providing water to our customers, shareholders and municipalities.  

SRP’s water portfolio 

Our water portfolio consists of surface water stored in reservoirs and underground recharge facilities as well as groundwater pumped from wells, all of which contribute to a more secure water future for the Valley. 


There are more than 270 wells in SRP’s system. We regularly adjust how much water is pumped based on how full our lakes are. This helps us maintain a proper balance among our water storage systems. 

Groundwater recharge 

Another contributor to our water resource mix is our operation and maintenance of two underground storage facilities. Our partners, consisting of local municipalities and tribes, accrue long-term storage credits when water is recharged that allow them to use this water in the future.  

Our two underground storage facilities are the Granite Reef Underground Storage Project (GRUSP) and the New River-Agua Fria River Underground Storage Project (NAUSP). These storage sites store the water in an aquifer, a porous layer of underground rock that can hold and release water when it’s needed. During wet years, extra water is stored underground and acts as somewhat of a “savings account.” That way, during dry years, SRP’s recharge partners can withdraw this stored water and continue to meet water needs. 

Fun fact: Combined, our underground storage facilities can recharge nearly 20 billion gallons per year. 

Surface water in reservoirs 

Surface water in the reservoirs is our main water resource. This is our most renewable method of water storage. Water from the Salt and Verde rivers, as well as from East Clear Creek, flows over our watershed, making its way to our seven reservoirs where it is stored. Altogether, these reservoirs can hold up to nearly 750 billion gallons of water. 

One of the most vital reservoirs in our system is Theodore Roosevelt Lake. This reservoir alone can hold 1.6 million acre-feet of water, making it responsible for delivering over half of the Valley’s yearly water supply. 

Water releases and runoff 

We occasionally need to release water that is stored in our reservoirs to manage capacity. We may see our reservoirs reach capacity after we have a lot of snow in the winter that melts quickly with a warmer rainstorm or when temperatures rise in the spring. Water releases are measured by the quantity of water and how quickly that water flows in cubic feet going down the system per second.

During a water release, dam operators at the reservoir open gates and valves which allows the water to flow down the river channel. A small portion of this water is ultimately absorbed and naturally recharges the groundwater aquifer. Depending on the quantity released, these water releases can result in temporary road closures where roadways enter washes. In instances of heavy water releases on the Salt River from Roosevelt, the water flow produces renewable hydropower 24/7, which is called run-of-river generation. 

In advance of water releases, SRP works with municipality partners to promote safety in areas that will be affected. There is an established notification procedure in place to provide information to local government entities, emergency managers and other agencies to ensure public safety at all levels of a water release. 

Water release at Theodore Roosevelt Dam

Water for the future 

All of SRP’s water storage works together to better prepare Arizona for future droughts. Learn more about how we manage water in the desert. 

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