Kootenai River Study
Status: Active
In 2005, the U.S. Geological Survey (USGS) developed a one-dimensional hydraulic-flow model of a 65.6-mile reach of the Kootenai River in Idaho (Berenbrock, 2005). The primary focus of the model was to locate the transition point between backwater and free-flowing water in the Kootenai River because many biologists believe that hydraulic changes at the transition affect the location where sturgeon choose to spawn.
The modeled reach starts at Leonia near the Montana/Idaho border and ends at Porthill near the United States/Canada border. The modeled reach also encompasses the white sturgeon spawning habitat reach (river mile 139.8 to 153.3) that has been designated as a critical habitat. The model has proven to be a useful tool to simulate hydraulic changes, especially in determining the location of backwater extent.
Concerned with enhancing white sturgeon spawning conditions in the Kootenai River, the U.S. Fish and Wildlife (USFWS) is deciding how far to extend the critical habitat reach upstream into the braided and (or) canyon reaches. The braided reach extends from U.S. Highway 95 Bridge at Bonners Ferry to near Crossport. The canyon reach extends from river mile 159.2 to Libby Dam. The streambed in the braided and canyon reaches is composed primarily of gravel and cobbles and is suitable for white sturgeon spawning. Whereas the meander reach (downstream of Bonners Ferry) of the Kootenai River is composed primarily of medium to fine sand, which is unsuitable for spawning.
In September 2005, the USGS, in cooperation with the USFWS, used the one-dimensional hydraulic model to aid the USFWS in deciding how best to extend the length of channel designated as the critical habitat reach. These additional simulations are needed to determine if hydraulic characteristics of the braided and canyon reaches are reasonable for white sturgeon spawning.
