Hebgen Dam malfunction causes dramatic drop in river flows, strands fish

Montana FWP and volunteers work to rescue fish, flows may not be restored for ‘several days’

Read an update to this story here.

By Gabrielle Gasser EBS STAFF

HEBGEN LAKE – Volunteers and Montana Fish, Wildlife and Parks staff gathered this morning to rescue fish on the upper Madison River after a malfunction in the Hebgen Dam caused a significant drop in flows. 

A gate component on Nov. 30 failed on the dam’s outlet structure, according to a Dec. 1 press release from dam operator NorthWestern Energy, which decreased the opening for the outtake of water at the bottom of the gate. The gate malfunction interferes with NorthWestern Energy’s ability to control river flows which led to the river dropping from 648 cubic feet per second to 228 cubic feet per second, according to United States Geological Survey data.

Hydro engineers and personnel from NorthWestern Energy have been working to develop a repair plan, according to the press release, and they are on site this morning working to restore gate functionality and river flows to the Madison River as quickly as possible.

While NorthWestern Energy works to repair the dam, FWP has issued a full fishing closure for the upper Madison River from Ennis Lake to Hebgen Dam. The closure was announced on the evening of Nov. 30 and according to Morgan Jacobsen, information and education program manager with FWP, the closure will remain in place until flows are fully restored to the river.

According to a Nov. 30 press release from FWP the impacts to the fishery are still unclear. Jacobsen said that the impact will take a while to become fully known.

“It is significant for sure,” he said. “There is still water in the channel but it is a significant drop.”

FWP staff and volunteers have been moving stranded fish along the upper Madison River into the main channel since this morning. Jacobsen explained that the biggest concern is spawning trout. The Madison River brown trout are currently spawning, meaning their fertilized eggs are being deposited into spawning beds in the river called redds. As low flows lead to dried up channels, redds are left exposed. 

“At this point, the biggest potential impact to those redds is going to be low temperatures at night,” Jacobsen said. 

Kelly Galloup, owner of Galloup’s Slide Inn located on the upper Madison River, has been witnessing the impacts of the low flows firsthand. When he walked out to the river this morning, Galloup said he saw approximately 200 people on the river trying to save the stranded trout.

“It’s quite heart wrenching to walk out there and see all of that,” Galloup said. “It’s just dry. It’s just frightening.”

Water was released over the dam’s spillway on Nov. 30 to provide a small increase to the river flow but it remains far below normal levels. There is no timeline on when repairs to the dam will be completed but a representative from NorthWestern Energy said in a Nov. 30 email statement that “river flows may not be fully restored for several days.”

“Safety and restoring full water flow to the Madison River as quickly as possible for the fishery is NorthWestern Energy’s priority,” the NorthWestern Energy press release said.