Post-implementation re-assessment of agricultural best management practices on watersheds of Conesus Lake: Effects on stream water chemistry and aquatic macroinvertebrate communities

Abstract

Nutrient pollution is the third largest source of impairment of water quality in rivers and second largest in lakes in the US according to the Environmental Protection Agency (EPA). Agricultural best management practices (BMPs) are intended to improve water quality, reduce sediment and nutrient runoff, and remediate the effects of altered hydrology. BMPs were installed in the early 2000s in the Conesus Lake watershed and have shown initial success in reducing nutrient runoff in agricultural watersheds; however, continued monitoring of watersheds was recommended to determine if the BMPs remained effective over time. We compared water quality of agricultural BMP streams to non-BMP and reference streams in the Conesus Lake watershed to determine if BMP streams have better water quality than non-BMP streams. We also determined if there are differences in water quality in the BMP tributaries compared to prior pre- and post-BMP implementation monitoring periods. In addition, we performed an aquatic invertebrate diversity and biotic index study to determine if BMP streams have healthier populations of aquatic macroinvertebrates than non-BMP streams. We observed higher nutrient concentrations and loss of nutrients in the agricultural streams rather than the reference streams. However, our hypothesis that BMP streams would be significantly better in terms of water quality than non-BMP streams was generally not supported. In our analyses of parameters over time for the BMP streams, we observed that concentrations and loss per hectare were some of the highest we have recorded for many analytes in most streams. We also observed that BMP streams in the Conesus watershed do not have healthier invertebrate communities than the agricultural non-BMP steams. In some cases, this is likely driven by BMPs no longer implemented (or changes in land use). This could also be driven by climate change, more frequent storm events, greater storm intensity, and due to the timing of these storms. Previous studies have shown mixed results on whether BMP practices remain effective over time. BMPs should be made available throughout watersheds due to how effective they can be in reducing nutrient pollution, but they should not be considered “the be all end all” as they only provide partial solutions to watershed issues.