LONG-TERM INCA SIMULATIONS FAVOR CLIMATIC OVER ANTHROPOGENIC IMPACTS ON A REDUCTION OF STREAM WATER SALINITY IN NEW YORK STATE

Since the 1950’s, road salts have been applied to paved surfaces in the United States, resulting in a precipitous rise in concentrations of chloride (Cl^-) measured in northeastern surface waters. This change has been the focus of numerous investigations. Traditionally, modeling studies have evaluated the regional impacts of altered salting practices, but have not incorporated long-term changes in climate such as changes in winter precipitation regimes. As climate change is expected to impact hydrogeology into the 21^st century, incorporating these impacts within biogeochemical models is imperative to provide robust and realistic projections of future anthropogenic impacts for land use planners and policy makers. To test how changing climate may alter chloride levels, we use the integrated catchment (INCA) model to simulate Cl^‑ concentrations in two branches of the Tioughnioga River in Upstate New York. Climate simulations from multiple GCMs were run over 30-year time periods (1961-1990; 2010-2039; 2040-2069; 2070-2099) coupled with dynamic land cover and population change. Our findings show that Cl^- concentrations will continue to increase over the next few decades. Notably, model predictions suggest that concentrations will begin to slowly decrease thereafter (around 2040-2069) as winter snowfall totals decline and aquifer contributions sustain streamflow. Shifting winter precipitation from snow to rain in future scenarios results in decreased annual road salt inputs to the watershed under all climate scenarios. Catchments with a high percentage of urban land undergo a less substantial shift in daily surface water Cl^- than those dominated by forest or agriculture, suggesting that human impacts and changing climate ultimately interact to shape future watershed responses.