Watershed assessment of portions of the lower Musselshell and Fort Peck Reservoir subbasins 2007

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Part of the Montana State Library collection. "Prepared for: Bureau of Land Management, Lewisatown [sic]\ Field Office." "May 2007" - cover Includes literature cited [p. 39-41] Agreement Number : To assist the BLM in resource planning, we conducted a multi-scale ecological assessment of nine watersheds in the Fort Peck Reservoir and Lower Musselshell River sub-basins northeast of Lewistown, Montana. The area occupied by the watersheds is diverse, ranging from Douglas fir and lodge pole pine forests to rolling grasslands to the sharply dissected, Ponderosa pine and juniper covered breaks around the Missouri and Musselshell rivers. The goal of the study was to provide both landscape-level assessments of watershed health and integrity as well as site-specific evaluations of wetland and aquatic condition within the 970,000 acre study area. This was accomplished using both broad-scale GIS analysis and field sampling. Our broad-scale GIS assessment examined underlying biological diversity, measured current conditions, and evaluated potential threats. Several key findings emerged from this analysis: The Armells Creek watershed is the most hydrologically and topographically complex of the nine watersheds, and natural land cover (forests, grasslands, shrublands and woody wetlands) is highest in the Drag Creek watershed. The Sacajawea (Crooked Creek) watershed has the least natural land cover in its riparian corridors, indicating significant riparian vegetation loss since presettlement times; The Blood Creek watershed has the highest road density, and the highest number of roads crossing streams. The Drag Creek watershed, which includes parts of the Musselshell River valley, has the highest observed levels of noxious weeds, with both leafy spurge and spotted knapweed present. Across all watersheds, grazing is the dominant land use; approximately 90% of the land is grazed, regardless of ownership type (private or public). Perennial streams, rivers and wetlands are uncommon. Most streams are intermittent or ephemeral, and most wetlands occur on the fringes or overflow areas of manmade ponds and reservoirs. Fine-scale rapid assessments focused on wetlands, ponds, springs and streams. We conducted assessments of Proper Functioning Condition at 43 sites and detailed aquatic surveys at seven lotic, seven lentic, and one mountain spring site. From those assessments and surveys, we found: Of the 43 wetlands assessed, seven were found to be in proper functioning condition, seven were not functioning, and the remainder were functioning at risk. Most (20) of the wetlands that were functioning at risk were stable; three exhibited an upward trend and four exhibited a downward trend. Sixteen of these wetlands were on land owned or managed by the BLM. Of these, one was in proper functioning condition, three were not functioning, two were functioning with a downward trend, and the remainder are functioning at risk but stable. With continued management, the trend on the stable wetlands should be upward. Given the percentage of BLM ownership in the study area, these proportions suggest that BLM-managed wetlands are in no better or worse condition than other wetlands. In our aquatic surveys, the highest site habitat scores were measured in the Sacajawea River watershed. With fish-based metrics, one lotic site ranked non-impaired, two were slightly impaired, one was moderately impaired, and two -- where fish were expected but not found -- were ranked severely impaired. With macroinvertebrate-based metrics, two of the lotic sites were non-impaired, four were slightly impaired, and one was severely impaired. We also identified several management opportunities to support wetland and watershed health: Although leafy spurge, spotted knapweed, Russian knapweed, and salt cedar are found in the study area, they are not yet widespread, so vigilant monitoring and control may still prevent their incursion into weed-free areas; Many permittees already follow good grazing management practices to protect wetland and riparian resources. Encouraging these practices, coupled with frequent utilization monitoring and the use of physical barriers where necessary, will help ensure the maintenance of wetland and riparian resources. Increased emphasis on habitat and recreation values in reservoir management could also improve wetland functions. The Woodhawk Creek watershed contains a wilderness study area, and continued management for maintenance of natural habitats will preserve or improve the watersheds condition. The Drag Creek watershed also has good potential to be managed for maintenance of natural habitat values. Oil and gas activities, even in surrounding watersheds, may impact the study area in the coming years. Proactive efforts to anticipate and plan for both direct (exploration and drilling) and indirect impacts (residential and recreational development) will reduce future risks to wetland and riparian resources
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