Through the Microsoft eScience Project, the Berkeley Water Center is developing a Water Cyberinfrastructure prototype that can be used to investigate and eventually manage water resources. The Water Cyberinfrastructure is developing in close collaboration between IT, physical science, and California water agency leaders. The value of the Cyberinfrastructure prototype will be tested through relevant end-to-end demonstration focused on important California Basins. The study region(s) are chosen based on several criteria, including availability of the data, importance of the problem that can be tackled given the cyberinfrastructure to California, leveraging opportunity, and scientific importance of the problems to be addressed. The BWC is currently building partnerships with several water representatives, such as the USGS, Sonoma County Water Agency, the Monterey County Water Resource Agency, and the NOAA National Marine Fisheries Service. Our objective with the California Water projects is to first assemble only the most critical components needed to address relevant science questions, rather than to initially create fully developed problem solving environments or construct a grand scale solution.