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Southern region proposes hypolimnetic siphon for Pangewich Lake to curb algal blooms
Summary
Southern Region staff asked Blue Ribbon and Habitat councils for under $100,000 this fiscal year to buy materials for a proposed hypolimnetic siphon that would remove nutrient‑rich bottom water from Pangewich Lake to reduce harmful algal blooms and fish kills; project partners include DEQ and local irrigators but some maintenance and agreements remain to be finalized.
Southern Region fisheries staff asked joint Habitat Council and Blue Ribbon members to help fund the early phase of a hypolimnetic‑siphon project at Pangewich (Pangewich) Lake intended to remove nutrient‑rich bottom water and reduce summer harmful algal blooms and fish kills.
Nick Braithwaite, fisheries biologist for the Southern Region, said the siphon would draw denser, nutrient‑laden water from the hypolimnion and route it for irrigation use rather than releasing warmer surface water at the dam. He said the concept could reduce late‑summer algal blooms and compressive thermal stress that can cause fish mortality.
"We thought it seemed like a good idea," Braithwaite said, describing modeling work the team performed with water‑quality staff. He told the councils the total project cost, excluding partner in‑kind support, is roughly $775,000 for engineering, pipe purchases and construction; the councils were asked for slightly under $100,000 this fiscal year to purchase materials so procurement can occur in FY27 and implementation be staged across two fiscal years.
Paul Burnett, nonpoint‑source program coordinator for the Utah Division of Water Quality, told the council his office has worked with Southern Region staff on technical analysis and monitoring plans. "That'll reduce the temperature in the stream below by about 2 degrees during the summer," Burnett said of modeled downstream benefits, and he confirmed a nutrient‑monitoring program will accompany implementation to check for downstream impacts.
Braithwaite said the project dovetails with other local efforts to reduce nutrient inputs — improved shoreline fencing, upstream sediment work after the Bridal Head Fire and septic‑system changes around lakeside cabins — and that water‑quality partners (including federal 319 and state nonpoint funds) have committed money to the effort. He noted two legal or contractual threads remain: a maintenance/agreement document with dam owners and a separate agreement with irrigators. "I think the agreement with the water users is with our GA office right now," he said, adding that the irrigators have been supportive in early discussions.
The councils did not vote in the morning session; members asked follow‑up questions about operational details, monitoring, and how siphon operation would be coordinated with irrigation seasons. Braithwaite said siphon operation would be designed to align with irrigation needs so that water removal does not conflict with users, and that the siphon would not be able to draw the lake below its natural level.
