Simulating California's water supply system under future climate stresses
Reclamation's Central Valley Project is coupled with the State Water Project on a monthly time step in the CalSim 3 model. This study will adapt CalSim 3 to use outputs from a climate model, the Intermediate Complexity Atmospheric Research (ICAR) model, as inputs, with the Variable Infiltration Capacity (VIC) runoff model as an intermediary.
The inputs to ICAR were generated by S&T project ID 1816, which produced ensembles of future climate simulations featuring cutting-edge research into orographic precipation and snow pack estimation. ICAR will help improve these results further by making possible a sensitivity analysis of improved microphysics schemes. The meteorological results will make the CalSim 3 analysis possible; they also improve our understanding of likely future impacts on water supply in their own right by improving our ability to model the West's climate across time. Completing this analysis promptly will continue the momentum of the research begun in S&T 1816 and allow Reclamation to direct needed research toward our needs. In this case, microphysics findings that will have impacts on models around the world would be generated over the Western US domain, ensuring Reclamation early access to the fruits of these findings.
As much of the range of results generated in S&T 1816 as possible will be transmitted through ICAR and VIC to CalSim 3. The CalSim 3 results will be analyzed (potentially through post-processors such as temperature models) for patterns in allocations, shortages, deliveries, regulatory compliance, and other water supply categories. They will quantify the potential effects of future climatology on both the Central Valley Project and the State Water Project. This includes likely effects for stakeholders, e.g. a change in the magnitude of shortages for south-of-Delta water districts. Analysis of the model network will help identify pinch-points in the system; statistics for dams, pumps, and other features of the model will be compa
Need and Benefit
Our main water supply model is calibrated to the historical record; we should calibrate it to climate model outputs, too. In S&T 1816 we developed climate models with this purpose in mind. We can generate weather on a monthly time scale and stress the current water supply system with realistic rainfall and snow distributions derived from future scenarios. We can find out how the system would respond to a drought or a whiplashing climate. This kind of modeling could inform decision-making about projects like dams with long operational lives.
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