Can SRP meet Valley’s water demand with reservoirs almost half empty?

PHOENIX — Salt River Project is confident that it has plenty of water to supply the Valley despite an unusually warm start to the year and low reservoir levels.

SRP delivers water from the Salt and Verde river watersheds to about 2.5 million people in metro Phoenix, over half of Maricopa County’s population.

Officials with the utility company said the system, which can meet demand for about three years when completely full, has proven to be resilient through dry years.

“Right now, we’re about half full. … If we had no more inflow, that’s still about a year and a half of water to meet demand,” SRP senior hydrologist Jake Richardson told KTAR News 92.3 FM.

How low is water level of SRP reservoirs?

The SRP Watershed Connection website shows current and historical data for six reservoirs, four on the Salt River and two on the Verde River. As of Tuesday, the entire system was 55% full. It was at 68% on the same date a year ago and hadn’t been below 60% in late April since 2018.

However, Richardson said the reservoirs have been much lower before, noting that the system was at roughly 25% capacity during drought in the early 2000s.

“We go through those periods where it’s wet, we’ll fill that [reservoirs]. And just as the natural climate cycles of Arizona, we have those dry years that we draw from the reservoirs during those years,” Richardson said.

After Arizona received a decent amount of rain in the fall, low snowpack in the winter and an unseasonably warm spring made it difficult for much of that water runoff to reach the reservoirs.

Roosevelt Lake, the largest reservoir in the SRP watershed, is currently 45% full. But just three years ago, SRP had to release large volumes of water from the system to protect dams and make room for ample runoff.

The water comes down from the reservoirs to Granite Reef Dam, where it’s then diverted to the Valley via the Arizona Canal and South Canal.

SRP system stays resilient through drought years

This is the time of the year when SRP measures its surface water resources and evaluates how much groundwater it will need to tap to meet demand.

The SRP watershed is less susceptible to hydrologic variability than Arizona’s other major source: the Colorado River.

“The Salt and Verde system, the reservoirs, have filled and spilled while the Colorado has continued to decline over years,” Richardson said.

The SRP system keeps flowing despite only nine years of average rainfall in the last 45 years.

“The reality is that most of them [the years] are dry. And then a handful of those are wet, and we rely on the wet years to get us through the dry years, and that’s the beauty of having a reservoir system like Roosevelt,” Richardson said.

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