More than a century ago, the founders of the Salt River Project (SRP) had a vision to build a dam and a reservoir that would allow people to thrive in the harsh desert of central Arizona. SRP has followed that original vision by expanding its system from a single dam—Theodore Roosevelt Dam—to a system made up of seven dams and reservoirs with a total storage capacity of more than 4 million acre-feet.
By Ron Klawitter
Today, SRP continues to build on that foundation through planning efforts intended to provide reliable water and power to the thriving Phoenix metropolitan area for another century.
With more than 8.3 million acres of watershed, SRP delivers more than 800,000 acre-feet of water annually from the Salt and Verde Rivers to 10 cities and towns as well as to agricultural customers.
Issues such as climate change, forest fires endangering the watershed, and a growing population can be daunting, but SRP is preparing to provide a reliable source of water not only today but in the future as well.
While research conducted by SRP and the Bureau of Reclamation shows the effects of climate change on the water yield of SRP watersheds to be relatively minor compared to the reductions that other western river basins may see, climate modeling data also show that Arizona can expect more extreme weather patterns; bigger floods; and longer, more-severe droughts. This means that maintaining SRP’s annual carryover storage capacity is critical to managing variations in river flows.
Water is precious in the desert, and every drop that can be stored during wet periods can help customers during dry periods. Over the years, however, the accumulation of natural sedimentation in the Verde River basin has significantly reduced the water storage capacity of one of the two reservoirs in the basin, Horseshoe Reservoir, creating uncertainty about SRP’s future water management capabilities. In fact, around 45,000 acre-feet of storage—nearly one-third of the reservoir’s original water capacity—has been lost to sedimentation. That volume could provide nearly 90,000 families with the water they need for a year.
This fall, Reclamation officials will conduct a study to evaluate possible ways to address this loss of storage capacity. The process will include meetings to receive input from stakeholders representing a broad range of expertise and interests.
SRP believes that, through this appraisal process, it will find a solution that helps meet the needs of central Arizona for the next century, ensures the resiliency of its system, and reduces central Arizona’s dependency on fossil groundwater.
While sedimentation is an issue on the Verde River side of the watershed, SRP officials are also looking at ways to make the Salt River reservoir system more efficient.
Theodore Roosevelt Dam is the largest dam in the SRP system, and Theodore Roosevelt Lake is its largest reservoir, with a capacity of more than 1.6 million acre-feet of water. The reservoir contains around 70 vertical feet of additional storage capacity above the conservation pool, representing space for an additional 1.8 million acre-feet. Current operational requirements dictate that SRP evacuate water in that area within 20 days, making it challenging to put flood waters to beneficial use.
The utility is working with Reclamation and the U.S. Army Corps of Engineers to evaluate options to improve the operational flexibility in the reservoir’s flood control space. This would allow SRP and its partners more time during the runoff season to put the water to beneficial use or to store it underground for later use. It would also provide an opportunity to improve the water security of communities in central Arizona that face potential future shortfalls based on expected demands or available supplies, such as those affected by shortage on the Colorado River.
These two projects play a critical role as we continue to prepare our infrastructure and operations for the future while also creating opportunities to help sustainably meet the water needs of Central Arizona.
As SRP prepares for the next 100 years, what will Arizona’s current water managers do to prepare for our children in the same way that the visionary leaders of the 20th century did? Armed with research and input from stakeholders and partnering with federal agencies and other agencies, SRP will continue to invest in its infrastructure to help improve the management of Arizona’s most precious resource.