The NOAA Earth System Research Laboratory (ESRL) and the Scripps Institution of Oceanography are implementing a five-year Memorandum of Agreement with the California Department of Water Resources (DWR) to create a 21st-century observing, modeling, display, and decision support system to help address California's flood protection and water resource issues. This work is based on nearly a decade of scientific research into the forcings of extreme precipitation and runoff events along the U.S. West Coast conducted under NOAA's Hydrometeorolgy Testbed (HMT; hmt.noaa.gov). The observing system being implemented as part of this project could be used potentially for satellite calibration/validation studies. Soil moisture is a key surface variable that can determine whether a storm produces a flood. This project will deploy 43 soil moisture stations across the state. Atmospheric water vapor is the fuel that feeds precipitation, and global positioning system (GPS) receivers offer a robust way to measure the vertically integrated water vapor (IWV) content over land. In addition, hundreds of GPS receivers are present in California for geodetic and other purposes. Retrofitting these receivers with surface meteorology sensors allows them to retrieve IWV. The DWR project will use the GPS technique to measure IWV at 37 sites across the state. HMT research has also shown the importance of the snow level in determining how runoff in a basin responds to a storm. Specifically for the DWR project, ESRL engineers have developed a new, low-cost radar designed to measure the snow level. These radars are being deployed at ten of the state's major reservoirs. Finally, HMT research has documented how the narrow plumes of enhanced moisture transport in atmospheric rivers (ARs) contribute to extreme precipitation and flood events. In response, ESRL scientists have developed an observing system called an atmospheric river observatory. The contract with DWR will deploy four atmospheric river observatories along the California Coast to detect and monitor at the surface and aloft the key parameters in ARs that lead to heavy precipitation and flooding. Most of the instrumented sites across this new statewide observing network will also have raingages. Status of the observing network implementation will be presented along with examples of data and products available from the network.