SRP Adds Another Tool In Efforts To Manage Its Water Supplies

by Peter Maloney
APPA News
November 10, 2021

Salt River Project (SRP) has teamed up with OpenET in its latest step in managing the forest resources that impact the watershed serving its utility water customers.

In October SRP formed a partnership with OpenET, a public-private partnership led by the Environmental Defense Fund, NASA, Desert Research Institute, and HabitatSeven.

OpenET provides an online platform that uses satellites to assess the evapotranspiration (ET) that occurs when water returns to the atmosphere through evaporation and transpiration, the water vapor given up by plants.

Having data available on how much evaporation is occurring gives SRP a greater understanding of the water budget and of how much water is turning into vapor and being transferred out of its system, Elvy Barton, forest management principal at SRP, said.

Evapotranspiration is an important consideration for SRP since the Arizona public power utility’s territory is largely a desert. When water remains in SRP’s territory it makes the landscape more resilient to droughts and wildfires. SRP operates seven reservoirs and dams that delivers water to 2 million customers.

There is also a correlation between evapotranspiration and unhealthy forests. Much of SRP’s water supply comes from 8.3 million acres of land in northern and central Arizona that is heavily forested. A lot of those forests are unhealthy, populated by either too many or stunted trees, making the forest vulnerable to wildfires, Barton said.

SRP first began to realize the scope of the problem in 2002, after the Rodeo-Chediski Fire burned a large swath of east-central Arizona. It was the worst fire in Arizona’s recorded history until the Wallow Fire surpassed it, burning over half a million acres in 2011.

In the wake of a wildfire, the land cannot absorb as much rainfall, creating the potential for dangerous floods and mudslides that can add silt and debris to streams and reservoirs that can impair water quality and add to water management costs.

SRP has been involved in forest restoration efforts for about a decade but stepped up its efforts in the past few years because of the growth of mega fires, which consume over 100,000 acres.

In 2019, SRP updated its sustainability goals to include forest restoration and adding a goal of partnering on thinning 50,000 acres of forest per year and 500,000 acres by 2035.

SRP is also working on the Cragin Watershed Protection Project, which allows the U.S. Forest Service to move forward with prescribed burns and forest thinning across the watershed. SRP is also participating in the Healthy Forest Initiative that allows its residential customers to invest $3 a month towards strategic forest thinning projects.

SRP has also invested in projects such as a light detection and ranging (LiDAR) research efforts in partnership with Northern Arizona University that provides real-time visual watershed condition and forest data. It is like a census for trees that can focus on individual trees and help identify the best candidates for thinning, Barton said.

SRP has now added OpenET to its toolbox. The utility plans to use the OpenET data to help understand three things: how evapotranspiration is affected by wildfires, how prescribed controlled burns affect evapotranspiration, and what effect forest thinning has on evapotranspiration.

“Having a healthy watershed benefits everyone,” Barton said, adding, “being proactive is far less costly than being reactive.”