The Integrated Impacts of Land Use and Extreme Hydrological Events on a New England Catchment

Climate change is expected to significantly strain coldwater fisheries across New England through annual increases in stream temperatures and changes in hydrological conditions. These stresses are being superimposed upon landscape-scale impacts on water quality and riverbed composition, potentially limiting the ability of coldwater streams to support the life-history requirements of coldwater fish. In an attempt to provide an assessment of the impacts of climate change and land use on the ecosystem services of coldwater fisheries, we conducted a long-term monitoring study of water quality, sediment loading, and stream temperature of the Green River, a characteristic New England coldwater fishery. Over the course of 18 months, near-daily water sampling was conducted for fecal and total coliforms, nutrients (phosphate, sulfate, and nitrate), wash load, and stream temperature. The study duration included two summer and winter seasons and involved sampling throughout a 100-year discharge event (>110 cms for the 110 square kilometer watershed). July was also the wettest month in the 129 year record, with >35 cm of total rainfall. The data were supplemented by a multi-year record of average daily stream temperatures during summer months. Our results indicate year-on-year increases in average daily summer temperatures and highlight the importance of short duration and intense precipitation events in mobilizing dissolved constituents and wash load. For instance, the 100-year discharge event was produced by 18 hours of precipitation that supplied >10 cm of rainfall from the remnants of Hurricane Elsa. Fecal and total coliform counts exceeded 200 and 1000 per 100 mL of water, respectively. Nutrient loading during this time period peaked to more than five orders of magnitude greater than average daily conditions. The impacts of climate change and land use on coldwater fish populations remain to be explored, but it is clear that these integrated stresses are constraining the spatial and temporal windows for the utility of coldwater habitat.