Testing and application of a two-dimensional hydrothermal model for a water supply reservoir: implications of sedimentation

Validation of a two-dimensional hydrothermal stratification model for 14 years for Schoharie Reservoir, N.Y., an impoundment that experiences substantial drawdown, is documented. The model is demonstrated to perform well in simulating the various features of the reservoir's thermal stratification regime in each of the years, including the timing and duration of stratification, the dimensions and temperature of the layers, and the periods of internal wave oscillations in stratified layers. The average root mean square error for temperature predictions for the 14 years is 1.30 ºC. The validated model is applied in a probabilistic manner to investigate the impacts of sedimentation on the temperature of the withdrawn water (T_w) that enters a stream with a salmonid fishery, and features of the stratification regime. The predicted effects of sedimentation include a shift toward higher T_w values, a shortening of the duration of stratification, and decrease in the depth of the epilimnion in fall. The effects on T_w are exacerbated for the reservoir because of localized sedimentation adjoining the intake that increasingly limits access to cooler layers.Key words: hydrothermal model, temperature, model, reservoir, water supply, model projections, sedimentation.