Driftless Area Streams in Karstic Agricultural Watersheds: Best Management Practices, Biotic Integrity, and Environmental Stressors

ABSTRACT: To protect streams in agricultural watersheds, best management practices (BMPs) are implemented to reduce or prevent contaminated runoff from reaching surface waters. Over the course of three growing seasons (2000–2002), this study assessed physical, chemical, and biological indicators of water quality at 13 total stream sites in two agricultural watersheds (Garvin Brook, Whitewater River) in southeastern Minnesota USA, where BMPs have been used for over 50 years prior to the study period. Some sites in both watersheds exhibited impaired water quality due to high turbidities, high levels of total suspended solids (TSS) and fecal coliform bacteria, and low fish and benthic macroinvertebrate biotic integrities. Non-metric multi-dimensional scaling of water quality indicators and principal components analysis of fish and invertebrate communities highlighted varying degrees of differences between watersheds. On average, Garvin watershed sites exhibited better water quality during 2000–2002 than sites in the Whitewater watershed, likely because more headwater reaches were surveyed in Garvin Brook. A fish community index biotic integrity (IBI) was significantly negatively correlated with turbidities, TSS, and fecal coliform bacteria levels, but the benthic macroinvertebrate community IBI was not correlated to any water quality indicator or to the fish IBI. More recent studies in these watersheds and current impaired waters listings continue to indicate significant and ongoing water quality issues, so continued water quality monitoring is needed in these two watersheds to highlight and prioritize problematic subwatersheds for future conservation efforts to reduce or prevent agriculture-related runoff from reaching the stream networks.