Climate Change Effects On the Greater San Joaquin River Basin, California

The Central Valley in California is one of the most significant agricultural production regions in the United States. However, this region is semi-arid making it vulnerable to climate variability and change. For this study, we use an integrated model (ParFlow) to simulate the Greater San Joaquin watershed, a significant portion of the Central Valley, including integrated groundwater and surface water flow and land-surface processes such as evaportranspiration and the land-energy budget.. The basin is bounded by the California Delta in the north, the Tulare Lake basin in the south, Sierra Nevada in the east, and Coast Ranges in the west. The domain area is 270 km x 220 km and is discretized with a lateral spatial resolution of 1km x 1km. The vertical extent of the domain depth ranges from a low point at approximately 500m below sea level in the valley up to the top of the Sierra Nevada Range (at 3,800m above sea level). The subsurface is discretized with a vertical resolution of 1m for a total of 29.7 M nodes. The model has been initialized, or “spun up”, using a distributed, atmospheric time series observations. ParFlow has also been coupled to the Weather Research and Forecast mesoscale atmospheric model (WRF). Both the ParFlow and ParFlow-WRF models have been simulated over the San Joaquin basin. The purpose of this model is to examine the influence of climate change and groundwater dynamics on the soil moisture and land-atmosphere energy balance. This study will also will be used to investigate the spatial and temporal interactions between land surface and lower atmospheric variables. Portions of this work are performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.