High Resolution Integrated Hydrologic Modeling for Water Resource Management: Tahoe Basin Case Study

Water resources in the high altitude, snow-dominated Tahoe basin are susceptible to long-term climate change and extreme climatic events due to large inter-annual climate variations. Lake Tahoe and its contributing watersheds exhibit high climatic (precipitation, temperature) and hydrologic (streamflow, evaporation) variation that exert significant control over regional water supply on annual and sub-annual timescales. To adequately quantify these controls, a high resolution (300m) physically based integrated surface and groundwater model, GSFLOW, of the Tahoe basin has been developed to identify key hydrologic mechanisms that explain recent changes in water resources of the region. The model is parameterized using geographical datasets and maintains a balance between (a) accurate representation of spatial (e.g., geology, streams, and topography) and hydrologic (groundwater, stream, lake, and wetland flows and storages) features, and (b) computational efficiency, which is a necessity for exploring critical vulnerabilities of water-supplies in the region. The calibrated model reproduces multiple observations of streamflow, snow water equivalent, satellite derived snow covered area, lake stage, and groundwater head. Climate input uncertainty was significantly decreased in the model through incorporating additional precipitation station data and helped improve model simulations of observed fluxes more than adjusting model parameters alone. The model simulates fluxes at the outlet of the watershed, but is also consistent at simulating streamflow at internal nodes. This integrated modeling framework helped assess both surface and groundwater resources in a coupled manner in the Tahoe basin.