DWR has many programs and data tools to collect and disseminate information on water resources.
All Water Data Topics… http://www.water.ca.gov/nav/nav.cfm?loc=t&id=106
California Data Exchange Center (CDEC)
With the cooperation of over 140 other agencies, the CDEC provides real-time, forecast, and historical hydrologic data. This data includes water discharge in rivers, water storage in reservoirs, precipitation accumulation, and water content in snow pack, primarily focused in flood management. However, the data is also helpful for determining general water availability and natural supply trends.
More about CDEC http://cdec.water.ca.gov/
California Irrigation Management Information System (CIMIS)
CIMIS is a network of over 120 automated weather stations in California. CIMIS was developed in 1982 by DWR and the University of California, Davis to assist California's irrigators to manage their water resources efficiently.
More about CIMIS http://wwwcimis.water.ca.gov/cimis/welcome.jsp
Water Data Library
The library provides geographic-based data on water conditions.
More about the Water Data Library http://www.water.ca.gov/waterdatalibrary/
Interagency Ecological Program
The Interagency Ecological Program (IEP) provides ecological information and scientific leadership for use in management of the San Francisco Estuary.
More about IEP http://www.water.ca.gov/iep/
Integrated Water Resources Information System (IWRIS)
IWRIS is a one stop shop for state-wide water resources information. It integrates multi-disciplinary data to support Integrated Regional Water Management.
More about IWRIS http://www.water.ca.gov/iwris/