California's aging water supply and flood protection infrastructure is being challenged by the effects of age, increased standards for urban flood protection, and projected climate change impacts. In addition, there is a built-in conflict between providing flood protection and the other functions of major water storage facilities in California: water supply, water quality, hydropower generation, water temperature and flow for at risk species, and recreation. Flood protection is provided by keeping empty flood control storage space behind the dams during the flood season. All other users would prefer fuller reservoirs, if possible. In order to accomplish this goal, improved forecasts of precipitation, especially during extreme events, will be required.

The California Department of Water Resources (DWR) has signed a five-year agreement with NOAA's Earth System Research Laboratory (ESRL) to bring 21st century observation and modeling capabilities to bear on the state's water resource and flood protection issues. The joint project between DWR, NOAA, and the Scripps Institution of Oceanography is part of DWR's Enhanced Flood Response and Emergency Preparedness (EFREP) project. The underlying goal of the project is to improve precipitation forecasts, especially during extreme events. The planned statewide deployment builds on NOAA's Hydrometeorological Testbed (HMT) project carried out in the North Fork of the American River over the past three years. The planned deployment of instrumentation represents the first tier of a proposed multi-tier program. Taking full advantage of the new measurements will require a complementary effort in data assimilation, modeling and display. Decision support tools to integrate this new information into flood forecasts will also be developed.