Bioassessment of the West Branch of the Wolf River

Abstract

A total of 120 aquatic macroinvertebrate samples were collected during the spring and fall of 2005 from 20 sampling sites located on six separate streams throughout the West Branch of the Wolf River (WBWR) watershed, Menominee County, Wisconsin. Individuals were identified to the lowest taxonomic level, and 12 macroinvertebrate metrics were calculated including the Biotic Index (BI). In addition, five categories of riparian land cover were calculated for comparison with three other Wolf River Basin watersheds. The objectives of this study were to establish baseline biological water quality data for the WBWR watershed using rapid bioassessment techniques. The second was to asses the affects of the Neopit Mill Pond impoundment on the WBWR, and the third objective was to investigate the potential of the WBWR watershed serving as a bench mark for this region of Wisconsin. The results of this study ranked water quality at most sites throughout the WBWR watershed as excellent during the spring and fall of 2005. However, sites directly below the Neopit Mill Pond dam had degraded water quality compared to upstream sites. Changes in macroinvertebrate community structure were also observed immediately below the impoundment which had significantly more filter-feeders (p<0.05) and less gatherers (p<0.05) than upstream sample sites. Water quality at sample sites 7.1 km and 13.2 km downstream from the dam gradually returned to pre-impoundment levels following a continuum of longitudinal, spatial, and physical characteristics in most instances. Consequently, the water quality of the WBWR had no apparent impact on the Wolf River. The West Branch of the Wolf River was compared to three other Little Wolf River watersheds to determine if the WBWR was unique among other Wolf River Basin watersheds. Overall the water quality was classified as excellent in the WBWR compared to very good in the other Little Wolf River watersheds. Land cover within the WBWR had little urban development, more forest, and less agriculture and grassland than other Little Wolf River watersheds. Therefore, these results suggest that most WBWR sites, with the exception of sites immediately downstream from the Neopit Mill Pond dam, could be used as regional bench marks of high water quality for future regional management plans and comparisons with other watersheds in this area of Wisconsin.