NorthWestern: Drought conditions mean lower water levels at Hebgen Reservoir

Drought conditions are resulting in lower water levels at Hebgen Reservoir to protect fisheries on the lower Madison River, NorthWestern Energy said in a news release Monday.

“Current drought conditions, the result of low snowpack, low spring precipitation and recent hot, dry weather have led to challenging low water conditions in the Madison River system,” the utility said.

The news release described the following:

Water releases from Hebgen Reservoir feed Ennis Reservoir to support pulsed flow releases out of Madison Dam. The pulsed flow releases protect the lower Madison River from reaching lethal temperatures to fish. Hot, dry weather in June and July have required almost daily pulses. Pulsed flows have so far kept river water temperatures at safe levels this summer.

The pulse flows are calculated using a model that helps determine the volume of water to be released, allowing for the conservation of water while maintaining safe water temperatures in the lower Madison River.

Forecasts and modeling were closely followed by NorthWestern Energy to capture as much water as possible this spring, but limited snowpack and spring precipitation prevented Hebgen Reservoir from filling fully. Very hot temperatures began the end of June requiring water releases from Hebgen Reservoir to maintain safe temperatures in the Madison River for the fish population, which includes rainbow and brown trout.

“These low water years are especially challenging to meet all the needs of the various stakeholders on the Madison River system,” NorthWestern Energy Director of Hydro Operations Jeremy Clotfelter said in a statement. “There simply is not enough water to go around. The cooperation and flexibility of all really help to protect and maintain the long-term health of the river system, which is our priority. ”

Current water levels at Hebgen Lake and flows and water temperatures are available at http://madisondss.com/page/dashboard.php. NorthWestern Energy updates the webpage daily.

Property owners in the Hebgen Lake area and recreationists who use the reservoir should anticipate low water levels through the end of the year.

“NorthWestern Energy’s stewardship responsibilities of the river resources include balancing the many interests of multiple stakeholders,” said Clotfelter in a statement.

Low flows typically affect the amount of electricity generated, but this year, NorthWestern Energy’s Madison Hydroelectric plant is off-line for a planned major upgrade and will not be back in service until spring 2022.

NorthWestern Energy is working with the Federal Energy Regulatory Commission, Montana Fish Wildlife & Parks, the U.S. Forest Service, the U.S. Fish & Wildlife Service and other stakeholders.