Modifying agricultural water management to adapt to climate change in California's central valley

Climate change impacts and potential adaptation strategies were assessed using an application of the Water Evaluation and Planning (WEAP) system developed for the Sacramento River basin and Delta export region of the San Joaquin Valley. WEAP is an integrated rainfall/runoff, water resources systems modeling framework that can be forced directly from time series of climatic input to estimate water supplies (watershed runoff) and demands (crop evapotranspiration). We applied the model to evaluate the hydrologic implications of 12 climate change scenarios as well as the water management ramifications of the implied hydrologic changes. In addition to evaluating the impacts of climate change with current operations, the model also assessed the impacts of changing agricultural management strategies in response to a changing climate. These adaptation strategies included improvements in irrigation technology and shifts in cropping patterns towards higher valued crops. Model simulations suggested that increasing agricultural demand under climate change brought on by increasing temperature will place additional stress on the water system, such that some water users will experience a decrease in water supply reliability. The study indicated that adaptation strategies may ease the burden on the water management system. However, offsetting water demands through these approaches will not be enough to fully combat the impacts of climate change on water management. To adequately address the impacts of climate change, adaptation strategies will have to include fundamental changes in the ways in which the water management system is operated.