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Streams, rivers, lakes and reservoirs are important natural resources for irrigation, public supply, wetlands and wildlife.  Excess precipitation that flows into these sources is called runoff, and it's an important drought indicator.  The California Water Science Center tracks both monthly and annual runoff. 

Careful observation and analysis of the movement and condition of surface water is essential for understanding this resource, especially during times of drought. The California Water Science Center uses a network of more than 500 streamgages to collect real-time data on surface water at locations across the state.

In order to understand the integrated hydrologic systems in the San Antonio Creek Valley, many different types of data are being gathered from both the surface water and groundwater system. Learn about these data types and explore them with the interactive map.

The USGS models shown on this site are in the public domain, and are freely available. They are based on MODFLOW and other public-domain USGS software. Links to publications and web resources associated with each model are shown in the table next to the model map. The associated model files for some of these models are currently available via download.

The Lower Colorado Monitoring Network is a series of groundwater-level and water-quality wells, as well as streamgages and micro-gravity sites. This interactive map displays the sites and provides links to the most current data.

In California, land subsidence—mostly from groundwater pumping—was first documented by the USGS in the early 20th century. Completion of State and Federal water projects that bring water from California's wet north to its dry south allowed some groundwater aquifers to recover, and subsidence decreased in these areas. Subsidence continues today, sometimes at high rates of more than 1 foot/year.

This interactive webmap plots water-quality data from domestic and public-supply wells sampled by the USGS for the California Groundwater Ambient Monitoring and Assessment (GAMA) Program Priority Basin Project (GAMA-PBP), and allows users to download datasets. The GAMA-PBP is a cooperative program between the California State Water Resources Control Board and the U.S. Geological Survey. 

Interactive map of the Mojave and Morongo groundwater basins.  Data layers include sites and data for groundwater levels, water quality, and land subsidence.  Groundwater data spans 1994 to the present.

Map of the San Diego Hydrogeology project study area with links to groundwater and surface water data for each of the monitoring sties. 

During the recent droughts of 2007-2010 and 2012-2017, groundwater pumping has increased from the combined effects of the drought and land-use changes, re-initiating land subsidence. In order to document historical subsidence and monitor continued changes, the USGS has gathered and interpreted data from a variety of sources.