Fish & wildlife Success stories Hungry Horse

Success stories — Hungry Horse Dam Mitigation

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The Hungry Horse Mitigation Program, sponsored by Montana Fish, Wildlife and Parks, began in 1992 to address fish losses associated with the construction and operation of Hungry Horse Dam. The dam isolated approximately 38 percent of the Flathead Lake drainage and changed the physical and biological characteristics of the lake and river. The program's goals are to restore and reconnect critical habitat, reduce the negative interactions between native and non-native fish, and improve dam operations for native trout recovery.

The Flathead River system in Northeast Montana is a regional stronghold for migrating westslope cutthroat trout, part of Montana's natural heritage. Installation of the dam completely blocked fish migrations from Flathead Lake to the South Fork Flathead River upstream. In order to improve fish passage to critical spawning and rearing habitat, the program initiated several culvert replacement projects. These combined projects re-opened 16 percent of the available spawning and rearing habitat to migratory fishes in the reservoir system, and monitoring surveys have shown significant increases in adult and juvenile fish upstream of each passage improvement site. The program is also using innovative natural channel restoration techniques to improve native fish habitat throughout the upper Flathead River drainage. In one instance, improvements to Emery Creek included removing sections of a logging road that had distorted the natural meandering of the stream, causing habitat degradation and creating barriers to fish migration. The improvements enhanced fish habitat and restored a two-mile section of channel to aid the spawning and rearing habitat for native trout.

Dam operations had also created unnatural flow and temperature fluctuations in the Flathead River downstream of Hungry Horse Dam. In 1996, a temperature control structure was installed on the dam to correct the problem. It allows dam operators to take water from the appropriate depth in the reservoir so the water flowing through the dam turbines matches the natural, seasonal temperature pattern in the river. As a result, normal temperatures were restored in the Flathead River downstream of the dam, helping to increase favorable stream and habitat conditions for fish.

culvert modifications: before		after