- A 650-pound flume was installed by helicopter in a remote area.
- The device will provide accurate flow data for the Verde River in central Arizona.
- Results will help guide water supply planning and forest restoration.
Thursday, September 25, 2025 — Yesterday, the Salt River Project (SRP) announced the installation of a hydrologic flume in the Verde River
watershed of central Arizona. The Verde River is one of the main tributaries feeding the Phoenix-area reservoir system, and the new device will help measure inflows that eventually reach homes and businesses in the Valley.
The aluminum structure, weighing about 650 pounds, is designed to measure streamflow in an area that is nearly impossible to reach by ground. The flume, measuring roughly 10.5 feet by 9 feet, was modified with a custom heater to prevent snow and ice buildup during freeze–thaw cycles. This addition is expected to improve accuracy during winter and spring runoff periods.
SRP welders adapted the device so it could be lifted by helicopter and lowered into position, underscoring the logistical challenges of monitoring remote headwaters.
Why Measurement Matters.
Water from the Verde River, along with the Salt River, feeds into reservoirs that supply more than 2.5 million residents of the Phoenix metropolitan area. Tracking inflows into these reservoirs is essential for long-term planning, especially after a winter in 2023 that delivered abundant snow followed by a record-dry runoff season the following year.
“You can’t manage water if you don’t measure it,” said Zac Keller, Hydrographic Scientist at SRP. Keller emphasized that monitoring streamflow helps SRP respond to unpredictable weather shifts and maintain the stability of its reservoir system.
Research and Restoration.
Beyond water supply management, the new flume will serve as a research tool. SRP engineers are collaborating with graduate students at Arizona State University to investigate the impact of forest thinning on water yield. By comparing measurements before and after thinning projects, hydrologists aim to gain a deeper understanding of how restoration affects watershed health.
The water measured at the site flows from Sycamore Creek into the Verde River, eventually contributing to the supply available to Valley households and businesses.
Broader Context.
SRP manages a 13,000-square-mile watershed, an extensive system that includes reservoirs, canals, wells, and irrigation laterals. Each year, the utility delivers more than 244 billion gallons of water—about 750,000 acre-feet—through this infrastructure. The new flume is the first of its kind for SRP, and its performance will determine whether similar devices are deployed in other locations.
FAQ
What is a flume?
A flume is a specially designed channel or structure that measures the flow of water in a stream or river. By directing water through a known shape, hydrologists can calculate flow rates with precision.
Why was a helicopter used?
The installation site in the Verde River watershed is extremely remote and inaccessible by road. A helicopter was the only practical way to deliver and set the 650-pound structure.
Why does SRP need to measure this water?
Accurate flow measurements allow SRP to manage reservoir storage and delivery for millions of people in the Phoenix area. This helps the utility respond to droughts, wet years, and climate variability.
How does forest thinning tie into water supply?
Forest thinning can reduce wildfire risk and alter how much snowmelt or rainfall reaches streams. Measuring flow before and after thinning provides data on whether these projects increase water yield or simply change its timing.
How large is SRP’s service area?
SRP manages a watershed of 13,000 square miles and supplies water to about 2.5 million people in central Arizona, making it a critical player in the state’s water system.
