SRP installs unique flume to better monitor water that ends up in Valley supply

PHOENIX – Salt River Project (SRP) recently installed a first-of-its-kind hydrologic flume in northern Arizona to measure how much snowmelt makes it into the watershed.

“This is going to help us to understand climate change and forest thinning in these forested watersheds,” said Zachery Keller, an SRP hydrographic scientist.

The water yield from winter snowmelt is what makes up a large chunk of the Valley’s water resources. The flume will help measure the runoff volume and how much water is being lost to evaporation or absorbed by the soil, which scientists say has been impacted by climate change.

The ground in northern Arizona has become so dry it acts like a sponge and absorbs more surface runoff than it used to, so less water makes it to watersheds like the Verde River, where the flume was installed last month.

The flume will also help SRP figure out if prescribed forest thinning conserves water runoff because there are fewer trees to absorb it.

“One of the biggest fluxes of water in our ecosystem up north is evapotranspiration, which is the flux of water in the atmosphere moving up by plants,” Keller said.

What makes this SRP flume unique

The 650-pound aluminum flume is situated south of Williams near Bill Williams Mountain in White House Lake.

It includes a heating element to get a more accurate read of water flow in the winter and spring. Measuring 10.5 feet by 9 feet, it was delivered via helicopter and hoisted into position.

It contains precipitation gauges that measure rainfall and snowfall as well as soil moisture gauges and different instruments to track evapotranspiration.

A cosmic ray neutron sensor still needs to be installed. It will measure soil moisture over broader areas, as well as the amount of water in the snowpack.

SRP aims to deploy more flumes

SRP reservoirs provide water to more than 2.5 million Valley residents. To better manage the supply, the utility company plans to replicate the new flume in other areas along its 13,000-square-mile watershed.

“We plan to copy and paste this into other watersheds. And we want to do it in the Salt and even the Cragin watershed,” Keller said.

The flume is currently operational and ready for flow. Keller said it can detect water in the watershed from recent monsoons, but the important data will be read in the spring when the snow melts and the watershed fills.

“You can’t manage it if you don’t measure it,” Keller added.

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