Modelling potential effects of climate change on winter turbidity loading in the Ashokan Reservoir, NY

Abstract

AbstractRecent studies have indicated that potential future climate change may lead to changes in the timing and quantity of snowpack accumulation and winter (November to April) streamflow patterns including increased streamflow and turbidity in early winter and a slight reduction in turbidity loads at the time of traditional early spring run‐off. In this study, we examine the potential effects of these predicted changes on reservoir turbidity levels. Our analysis focuses on Ashokan Reservoir, NY, which can at times receive significant watershed turbidity inputs mainly from stream channel erosion from the Esopus Creek. Both measured and simulated turbidity loads and climatology are input to CE‐QUAL‐W2 (W2), a reservoir turbidity transport model that can simulate reservoir turbidity and other water quality parameters. The W2 model is applied to estimate the effects of hydroclimatology on effective settling rates and turbidity transport as a result of differences in reservoir thermal structure during summer and winter events. Simulations suggest that the effective settling velocity is substantially lower at low temperatures during winter time. Winter average stream flow is simulated to increase by 12% and 20%, which leads to increases in reservoir turbidity by 11% and 17% for the future period 2046–2065 and 2081–2100, respectively. From a seasonal perspective, a change in timing of peak streamflow with increased flows during the winter and slightly reduced flows during early spring leads to increased average reservoir turbidity during winter and slightly decreased in‐reservoir turbidity during early spring and summer. Copyright © 2013 John Wiley & Sons, Ltd.