MEDIA ADVISORY
Full Roosevelt prompts SRP water releases
Storage restrictions start as first time flood control space reached at lake
What's turned into an unexpected second consecutive wet La Nina winter has brought the level at Roosevelt Lake to its highest-ever elevation. And with another bountiful winter runoff comes another first for SRP, storage restrictions, which will prompt the release of water starting today into the Salt River through the Valley because the lake is now too full.
With the four reservoirs on the Salt River all nearly full at the early stages of the January-to-May runoff season, additional precipitation or runoff from melting snow will soon bring the elevation of Roosevelt Lake into uncharted territory -- and with it a second consecutive runoff year of excess water releases into the Salt River.
The water releases, while relatively small at 300 to 500 cubic feet per second, will have some impact on Valley residents once the water reaches the Phoenix metropolitan area in a few days. After the water is spilled from Granite Reef Diversion Dam east of Mesa and moves west down the Salt River, the river crossing at McKellips Road will likely be closed through the spring.
Releases into the Salt River last winter and spring were the result of not enough storage space in the relatively small Horseshoe and Bartlett lakes on the Verde River, but this winter's runoff will bring the elevation of 98-year-old Roosevelt Lake for the first time ever to 2,151 feet -- and likely higher.
A Roosevelt Lake elevation greater than 2,151 feet - which is considered full - is designated as Flood Control Space, as regulated by the Army Corps of Engineers' Water Control Manual. The Corps' Water Control Manual specifies release rates during the rising and falling stages of storage at Roosevelt Lake and a 20-day drawdown period to meet environmental requirements.
"Our plan is to start releasing smaller amounts of water -- just before Roosevelt Lake reaches elevation 2,151," said Charlie Ester, SRP's manager of Water Resources. "That will allow us to see how much runoff we get from these next storms without having to take too much water into the Flood Control Space - water that we would have to release after a 20-day period. Capturing water in wet years for use in dry years means the SRP reservoir system is doing exactly what it was designed to do."
These early February storms follow one of the wettest Decembers in SRP history, when more than 4.3 inches of precipitation fell on the Salt and Verde watersheds in December 2008. That total ranks as the 11th highest on record during the past 110 years. The median amount of precipitation for the December-through-March period is 6.25 inches, which means nearly 70% of the median was achieved with three months of the winter season to go.
The wet La Nina runoff season has significantly improved SRP's water-supply situation. The reservoir system on the Salt and Verde rivers stands at 93% of capacity, compared to 84% a year ago. Roosevelt Lake, which holds about 70% of SRP's reservoir system storage capacity, has reached 99%.
Roosevelt Lake is currently only inches from its maximum storage capacity and at its all-time high elevation. Runoff into Roosevelt now has filled New Conservation Storage space, which consists of 272,500 acre-feet of space behind Theodore Roosevelt Dam that is allocated for the Valley cities of Chandler, Glendale, Mesa, Phoenix, Scottsdale and Tempe. This is the third time water has been stored in this space since the completion of a modification project in 1996 that raised the dam 77 feet.
SRP is the largest supplier of raw water in the greater Phoenix metropolitan area, normally delivering more than 1 million acre-feet annually.
