 Weaver Slough, located north of Somers, south of the Flathead River and southeast of Kalispell, is one of six naturally created oxbow lakes associated with the previous course of the Flathead River. This portion of the Flathead Valley, south of Kalispell, is an important fly-way for migratory birds and a breeding area for several species of concern, including bald eagle, osprey, tundra swan and brown creeper. Weaver Slough is an important site for Canada geese, mallards, pintail, ruddy ducks, shovelers, pileated woodpeckers and kingfishers. It supports abundant populations of beaver, muskrats, river otter, and mink, and provides year-round habitat for ring-necked pheasants, wild turkeys, Hungarian partridge, and white-tailed deer.
Weaver Slough includes 200 acres, with approximately 150 acres of wetland/riparian habitat and five miles of shoreline along the slough. The shoreline is in excellent condition and densely vegetated with emergent vegetation and native shrubs. The interior of the slough contains several pothole wetlands, and cottonwood and aspen forest stands. The riparian corridor along Ashley Creek, between Weaver Slough and the Flathead River, is in good condition and is used widely by a variety of wildlife species, including grizzly bears, mountain lions, migratory waterfowl and songbirds. Weaver Slough can be viewed as one ecological unit comprising the slough, some of the riparian corridor on Ashley Creek, and extending south towards the lake, partially including the Blasdel and Flathead Lake WPAs. A number of elongated wetlands lie between Weaver Slough and the lake; most show signs of degradation from agricultural practices. Water from the slough is regulated by two dikes and used for irrigation. Water removal does not appear to greatly affect water levels. Due to Kerr Dam operations, water levels in Weaver Slough rise about a foot in the spring and drop again in the fall. This fluctuation in water levels is not believed to have any negative impacts.
Weaver Slough's wetlands may serve a filtering function similar to those found in the Blasdel Waterfowl Production Area (WPA) to the south. The WPA wetlands may function as discharge wetlands. Groundwater discharged into the wetlands evaporates leaving increased salinity concentrations in the wetland. Weaver Slough lies within the boundaries of the 100-year floodplain. The depth to the water table varies between five and fifteen feet. Water exchange between the slough and the Flathead River occurs through Ashley Creek, which contributes high nutrient loads to the Flathead River. It is therefore critical that wetlands and floodplain filtering functions be protected or restored if not fully functional. An intact strip of riparian and wetland vegetation around the slough provides important nesting habitat for birds and minimizes disturbances during critical migration periods. The area is privately owned and mostly farmed, except on the wetlands. There are presently four to five residences outside the slough, and none inside the slough.The open space provided by the farms still supports valuable wildlife habitat. Other nearby sloughs lack this degree of protection, and waterfowl production in those areas has declined. There are few remaining sloughs in the area, and the rivers ability to form new sloughs has been reduced by dams and development. Floodplain regulations apply to this area, but they are considered to be inadequate for protecting groundwater resources. Incompatible urban development surrounding the slough and Ashley Creek could potentially lead to water quality degradation of the river and lake. The wetland may partially filter some of the excess nutrients before they reach the Flathead River. However, no data has been collected to determine the extent of the benefits this slough may provide for water quality protection.
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