Groundwater Ambient Monitoring & Assessment (GAMA)

Science Center Objects

The Groundwater Ambient Monitoring and Assessment Program’s Priority Basin Project (GAMA-PBP) was established by the California State Water Resources Control Board (SWRCB) in response to the Ground-Water Quality Monitoring Act of 2001 (Sections 10780-10782.3 of the California Water Code). The USGS is the technical lead for the GAMA-PBP and between 2004-2012 focused on characterizing the quality of groundwater used by public water supply systems statewide. Beginning in 2012, the focus shifted to assessing groundwater quality tapped by domestic wells and small community-supply systems while continuing a long-term trend monitoring effort.

The GAMA-PBP work is organized by study unit with one to three study units started each year. It takes approximately three years from the time a study unit is begun until the data and final interpretive reports are published. Because the program is focused on completing the initial assessment of shallow groundwaters, only an extremely limited amount of repeat sampling as part of broad trends analysis is planned.


Current Focus

Domestic Wells

In 2019, the GAMA-PBP is focusing on domestic wells in the Eastern San Joaquin Valley groundwater basin and will be seeking well owner volunteers to participate in the study and receive a free chemical analysis of their well water. These results can be used to satisfy on-farm well sampling requirements of the irrigated lands regulatory program.

See if we need well owners near you! >>


Well Completion Report Database

The USGS is working with DWR and local entities to augment, and conduct quality assurance checks on, metadata for all well completion reports in the California Department of Water Resource's Online System for Well Completion Reports (OSWCR) archives as the GAMA-PBP moves through study units. Published data will include precise well locations (if they can be determined), perforation intervals, drilling date, etc. When the USGS publishes the datasets, they will be available here.


Interactive Map of Groundwater Quality Trends

Currently in development, this tool will allow the user to observe trends in inorganic constituents from the GAMA Priority Basin Project, alongside the same inorganic constituents from the SWRCB's Division of Drinking Water public supply drinking water data. Several trends options are included, as well as the ability to differentiate between statistically-significant increasing or decreasing trends, and trends dependent of well depth.


Accessing GAMA Results and Data

Explanations about why groundwater quality patterns exist are found in the interpretive products prepared for each study area. 

Raw data can be found through multiple portals:


screenshot of the user interface


USGS California GAMA-PBP Groundwater-Quality Results

Map-based portal for finding what we measured where.

Go to the map >>







map of California showing the GAMA province boundaries

GAMA Study Unit Reports

Individual data reports have been published for each of the GAMA study units:

Modoc Plateau and Cascades

Klamath Basin

North Coast Ranges

Central Valley

Sierra Nevada

Southern Coast Ranges

Basin and Range


Transverse and Peninsula Ranges

San Diego




screenshot of the NWIS California Water Quality Data landing page

USGS National Water Information System

The U.S. Geological Survey's (USGS) National Water Information System (NWIS) is a comprehensive and distributed application that supports the acquisition, processing, and long-term storage of water data. Water Data for the Nation serves as the publicly available portal to a geographically seamless set of much of the water data maintained within NWIS.

Go to NWIS >>









SWRCB GAMA Groundwater Information System (GeoTracker)

The State Water Resources Control Board's GAMA Groundwater Information System (GeoTracker) integrates and displays water quality data from various sources on an interactive Google-based map. Analytical tools and reporting features help users assess groundwater quality and obtain groundwater related information in California.

Go to GeoTracker >>