Active Monsoon Season Provided Record Runoff into SRP Reservoirs

This year’s monsoon season not only turned out to be one of the most active in the Valley in recent memory, it was also quite productive in terms of runoff into the Salt River Project’s watershed and reservoirs. The 2021 monsoon season provided nearly 250,000 acre feet of inflow into the Salt and Verde rivers’ reservoirs that are managed by SRP.

One acre foot of water is about 325,000 gallons – enough to meet the average demand of about three Phoenix metro households for one year.

This productive summer comes after a very dry winter, which brought in only about 103,000 acre feet of water—the second driest on record. This year’s monsoon also resulted in the wettest on record in terms of rainfall on the Salt-Verde system (July through August) since the 1950s and missed the all-time wettest monsoon in recorded history by just 0.02 inches.

“We know we have great climate variability in the Southwest,” said Charlie Ester, Manager of SRP Watershed Management. “The past two seasons demonstrate that by producing the second driest winter season ever followed by the second wettest summer season ever.”

SRP provides water for about 2 million people living in the Valley and provides nearly half of the Valley’s supply. Monsoon rains help to provide water to the watershed, lower fire risk across our national forest lands, and can be a welcome inflow of water into the reservoir system such as what has occurred this year.

While any runoff is a welcome sight for SRP’s hydrologists, they are happier with a productive winter as the watershed relies on winter rain and snow for the majority of the system’s water supply. And runoff season from last winter was the second driest among 109-year-old records kept by SRP water managers.

The Salt and Verde watersheds are made up of 8.3 million acres of protected forestland of northern and eastern Arizona. SRP also operates CC Cragin Dam that stores runoff from East Clear Creek that can be pumped into the East Verde River.

Despite the fact that the SRP system is not connected to the Colorado River Tier One shortage that will take effect in 2022, SRP officials continue to remind customers that the state is in the midst of a drought.

“Even though we’ve seen an increase in inflow into our system due to the monsoon rains, we were still at the highest demand of the year. While we are receiving inflow, we have also been releasing water primarily from the Salt reservoirs (including Roosevelt) to meet water demand within SRP’s service territory,” Ester said.

Water is stored in seven lakes in the SRP system and delivered through a series of canals to Valley cities where it is treated and provided to customers. The utility’s water portfolio includes surface and groundwater as well as water stored underground.