Reconstruction of Historical Inflows into and Water Supply from Shasta Dam by Coupling Physically Based Hydroclimate Model with Reservoir Operation Model

Abstract

Long-term water supply data are important for the current practice of water resources management at a target region. However, long-term water outflow data from reservoirs are typically limited at fine time resolution (hourly). In this study, the historical data on water supply from the Shasta Dam were reconstructed by a reservoir operation model with reconstructed reservoir inflow data. Before embarking on this exercise, first the inflow data were reconstructed by means of a watershed environmental hydrology hydroclimate model, with its input provided from historical atmospheric reanalysis data. The reanalysis data used in this study are from the National Center for Atmospheric Research and the National Center for Environmental Prediction (NCAR-NCEP) at spatial resolution of 2.5 degrees (210km at the modeled region). The NCAR-NCEP reanalysis data were dynamically downscaled to 3-km spatial grid resolution at hourly intervals by means of the regional atmospheric component of the hydroclimate model. The downscaled atmospheric data were then used as input to the hydroclimate model hydrologic module for the simulation of snowmelt and runoff conditions over Shasta Dam watershed. Then the reconstructed runoff from the watershed was used as input to a reservoir operation model for regulating outflow from Shasta Dam. The coupled hydroclimate model and reservoir model were successfully validated at Shasta Dam watershed by means of comparisons of the model simulations against the observations. Hence, the combination of proposed models were able to reconstruct the historical water supply data during a 60-year historical period (1950-2010) from Shasta Dam watershed.