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NorthWestern Energy says drought impacting dam operations

Hauser Dam
Hauser Reservoir
Missouri River
Posted at 6:15 PM, Apr 13, 2022

HELENA — NorthWestern Energy leaders say they’ve had to adjust their operations to account for lower precipitation they’ve seen this year.

“We’re sitting in a pretty challenging water year,” said Andy Welch, NorthWestern’s manager of hydro license compliance.

NorthWestern operates 11 dams across Montana, including nine along the Missouri and Madison Rivers. Because of that, they must pay close attention to water levels and runoff.

Welch says they were on trend for a relatively normal water year, until a change around the middle of January.

“We were right around the 30-year average, and then the precipitation just dropped off,” he said.

Currently, much of southwest Montana is seeing around 70% to 80% of its normal “snow water equivalent” in the snowpack. That could affect the spring runoff – and, by extension, hydroelectric energy production.

“The volume that we receive in the rivers definitely has an impact on how much we can generate,” said Welch. “Currently, we have a lot of units offline because the small volume in the river is not enough to use all of our units for generation.”

Last week, NorthWestern announced it would reduce water flows from Hebgen Dam, on the Madison River, through much of April. While Hebgen isn’t used for power generation, it is used for storage to help regulate flow along the Madison.

Hebgen Reservoir was about ten feet below full at the start of April, and the reduced flow is intended to help raise that level.

“The whole intent of doing that now is to try and capture more water in Hebgen Lake at a time when it’s less stressful on fish, so we can save that water for later in the year,” Welch said.

But for Hauser and Holter Reservoirs, near Helena, NorthWestern has less flexibility. They are required to keep those reservoirs within a foot of full, because of their operation agreement with the Federal Energy Regulatory Commission.

Welch says the most recent storm that came through Montana will be a help, but the effects aren’t clear yet, because snow totals varied so much from place to place. For example, he said the storm brought a lot of precipitation to the Tobacco Root Mountains that will feed into the lower Madison River. However, there was much less snow above Hebgen Dam.

“It’ll still benefit the system, but it won’t help contribute to the storage in Hebgen, as we had hoped,” Welch said.