(photo courtesy Salt River Project)

The Salt River Project reported it conducted an extended-duration spill gate test at Roosevelt Dam to confirm operational readiness in the event of flooding and gain valuable information on the dam’s ability to handle inflows from flood events.

After a wet and productive winter, Roosevelt Lake was at the highest level it has ever been, with water in its dedicated Flood Control Space, which is designed to slow down large floods. This was the third time this has happened since 1996. The spill gate test, conducted annually, ran longer than previous years to evacuate all the water from the Flood Control Space, as required by the U.S. Army Corps of Engineers.

Theodore Roosevelt Dam is the cornerstone of Salt River Project’s water-management system. The dam’s dedication event was held in March 1911. The 357-foot-high Roosevelt Dam is located on the Salt River, and power was first delivered on a permanent basis from the 36,000 kWh hydroelectric facility in 1909.

During the test, all four spill gates were open for the first 50 minutes, then the two spill gates on the right side (looking upstream) closed. The other two gates remained open for about two and a half hours. In total, the test released about 2,000 acre-feet of water downstream in Apache Lake. This is compared to a typical release, which consists of both gates being open for about 10 minutes and a release of about 5 acre-feet of water.

“This functional test, which is performed annually, is a sure-fire way to ensure the readiness of our water release capability,” said Ivan Insua, SRP’s director of hydro generation. “We will also be leveraging this season’s generous runoff by releasing some water in our Flood Control Space, which is above and beyond our normal conservation elevation, to perform an extended spill gate operation. This gives us very useful information on the gate and spillway performance.”

This past winter, snowpack on the 13,000-square-mile watershed that replenishes SRP’s reservoirs was the deepest it’s been in 30 years. More than 700,000 acre-feet of water have been released into the normally dry Salt River since March to ensure the reservoirs can handle all inflows from this winter’s snowmelt. Currently, the SRP reservoir system is at full capacity.

SRP is a community-based, not-for-profit public power utility in the Phoenix area serving about 1.1 million customers. SRP provides water to about half of the valley’s residents and manages a 13,000-square-mile watershed.