Sediment issue at Horseshoe Dam and Reservoir
The Verde River watershed covers nearly 7,000 square miles across central and northern Arizona. During storms and run-off events, sediment and debris enter the Verde River.
As sediment enters the Verde River, it is carried downstream to Horseshoe Dam and Reservoir. The reservoir slows and pools the river, providing an opportunity for the sediment to settle out of the water and accumulate on the bottom of the reservoir.
Horseshoe Reservoir water storage capacity
Because Horseshoe Dam and Reservoir is the first major water storage facility located on the Verde River, the reservoir collects the majority of the sediment transported by the river. SRP estimates that the amount of sediment that settles in the reservoir each year directly reduces the water storage capacity of the reservoir by 1,000 acre feet. That's enough sediment to cover a football field with sediment 1,000 feet high.
A preliminary sediment survey conducted in 2012 at Horseshoe Reservoir estimated that 45,749 acre-feet of capacity has been lost.
What's at risk
SRP uses the water storage capacity within its reservoirs to collect water for delivery to homes, businesses and farms in the Phoenix metropolitan area. Dams help collect water when it rains and snows in the mountains of northern and central Arizona. The reservoirs created by the dams enable SRP to deliver water every day–even in times of drought.
When sediment reduces water storage capacity in our reservoirs, it is harder for SRP to ensure there is enough water to meet the needs of Greater Phoenix during dry periods. Climate change is expected to bring more severe dry and wet periods to Arizona. Water storage capacity in reservoirs on the Verde River is a key component to ensure that SRP will be able to store water when nature provides it.
SRP's reservoir system has enabled safe and reliable water supplies for families, businesses and farms in the Valley of the Sun for more than a century. We are working to ensure that we have the tools needed to reliably deliver water for the next century.
What SRP is doing
The U.S. Bureau of Reclamation owns the dams and reservoirs operated and maintained by SRP, including Horseshoe Dam and Reservoir. SRP has asked that Reclamation conduct an appraisal study to evaluate options for restoring the storage capacity lost and to reduce future capacity impacts of the natural sedimentation process. This study is called the "Verde Reservoirs Sediment Mitigation Study" (VRSMS). VRSMS provides an opportunity for experts and interested stakeholders to learn more about this important issue and to provide input to Reclamation on potential solutions. In our arid desert environment, we cannot afford to lose the capacity of our water supply system.