Cheesman Dam: Happy trout, reliable water supply

Century-old workhorse dam keeps the water flowing and the temperatures just right for great fishing.

August 3, 2017 | By: Jay Adams

Water travels a maze-like path on the way to your faucet: from mountain snow to high-country streams, through reservoirs, dams and canyons.

Denver pioneers developed the elaborate delivery system as far back as the late 1800s, and today’s water managers know how to get additional benefits from every drop brought into the city.

Southwest of Denver, Cheesman Canyon is one example of how careful planning can get water to the tap while sustaining one of the state’s top trout fisheries along the way.

The mid-level jet valve serves as a backup water release and helps fine tune river temperatures below Cheesman Dam.
The mid-level jet valve serves as a backup water release and helps fine tune river temperatures below Cheesman Dam.

Denver Water uses a special feature at Cheesman Dam to help manage the temperature of the South Platte River at various times of the year.

Completed in 1905, Cheesman has three ways to release water from the reservoir: a spillway on the top, a mid-level release with a jet valve and valves at the bottom.

The mid-level valve’s primary function is to serve as a backup system to send water to treatment plants downstream when the main valves at the bottom need repairs.

“The jet valve is critical to the dam’s operations,” said Dave Bennett, water resource engineer. “We can also use it to warm up the river when it’s cold, or cool it down if it gets too warm for the fish.”

Fly Fishing guide Pat Dorsey shows off a rainbow trout in Cheesman Canyon.
Fly fishing guide Pat Dorsey shows off a rainbow trout in Cheesman Canyon.

“Water temperature is a huge component for a healthy fishery,” said Pat Dorsey, a long-time fishing guide on the South Platte River. “The healthiest temperature for rainbow and brown trout is between 50 and 60 degrees.”

Keeping the water in the optimum temperature range is good for fish metabolism and improves their ability to spawn, Bennett said.

Each level of the reservoir has a different water temperature. When water goes over the dam’s spillway, the temperature can top 60 degrees. The water released through the jet valve 60 feet below the surface is in the 50-degree range, and water from the bottom of the reservoir is in the 40s.

“What we try to do is blend those temperatures together to create the best environment for the fish,” Bennett said. “Temperatures in the 50s also trigger insects to hatch, providing food for the trout.”

Rainbow and brown trout are healthiest in 50 to 60 degree water.
Rainbow and brown trout are healthiest in 50 to 60 degree water.

Adding environmental factors into water delivery requires careful coordination between Denver Water’s planning division and Cheesman Dam operators. It’s a balance that involves juggling demand for water in the city, reservoir levels and dam maintenance with the appropriate time of year and conditions for the fishery.

Denver Water also has the ability to manage temperatures along the South Platte River at Eleven Mile Canyon Dam and coordinates stream flows with Aurora’s Spinney Mountain Reservoir to improve trout habitat through Eleven Mile Canyon. 

Denver Water manages water temperatures according to the South Platte Protection Plan, a cooperative regional project designed to protect and enhance the river.

“Healthy fish make for ideal fishing conditions,” Dorsey said. “That’s why this canyon is on every fisherman’s bucket list.”

2 thoughts on “Cheesman Dam: Happy trout, reliable water supply”

  1. I had no idea you guys could control the temp of a river! This was fascinating to watch.

    Love all these stories from Denver Water.

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