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GAMA – Groundwater Ambient Monitoring & Assessment Program
Priority Basin Project
The GAMA Priority Basin Project assesses groundwater quality in key groundwater basins that account for over 90 percent of all groundwater used in the State. Groundwater is monitored for hundreds of chemicals at low detection limits, including emerging contaminants such as pharmaceuticals and personal care products. The State Water Board is collaborating with the U.S. Geological Survey and Lawrence Livermore National Laboratory to implement the Priority Basin Project.
- See the Priority Basins: Map of Prioritized Basins
- See GAMA Priority Basin Project Status
- See Google map-based interface of groundwater basins, associated reports (including Bulletin 118 by basin, published geologic and hydrogeologic reports, published groundwater data reports), and groundwater quality data: GeoTracker GAMA
- See Priority Basins and Hydrogeologically Vulnerable Areas
- See GAMA Priority Basin Project Background Summary
- See a listing of all GAMA Groundwater Reports
- USGS GAMA Home
What is a Priority Basin?
GAMA Priority Basins consist of 116 of the 472 DWR defined groundwater basins in the state. GAMA Priority Basins are defined as groundwater basins that account for:
- 95 percent of all public supply wells
- 99 percent of all municipal groundwater pumping
- 90 percent of agricultural groundwater withdrawals
- 90 percent of all leaking underground storage tank sites
- 90 percent of all pesticide application in the state
- 60 percent of the land area in California
Many public supply wells are located outside the boundaries of a defined groundwater basin. To address these wells, the GAMA Priority Basin Project has included areas outside of DWR-defined basins such as areas of the Sierra Nevada and Mojave Desert.
Priority Basin Study Units and Sampling
The GAMA Priority Basin Project is grouped into 35 groundwater basin groups called “study units”. Each study unit is sampled for common contaminants regulated by the California Department of Public Health (CDPH), and also for unregulated chemicals. Testing for these chemicals – usually at detection levels well below those achieved by most laboratories – will help public and private groundwater users to manage this resource. Some of the chemical constituents that are sampled by the GAMA Priority Basin Project include:
- Low-level Volatile Organic Compounds (VOCs)
- Low-level pesticides
- Stable Isotopes of oxygen, hydrogen, and carbon
- Emerging Contaminants (pharmaceuticals, perchlorate, chromium VI, and other chemicals)
- Trace Metals (arsenic, selenium, lead, and other metals)
- Radon, radium, and gross alpha/beta radioactivity
- General Ions (calcium, magnesium, fluoride)
- Nutrients – including nitrate, and phosphates.
- Bacteria - Total and Fecal Coliform bacteria
To see which Priority Basins have been sampled, and to read the available reports, please visit the following:
- Map of Prioritized Basins
- GAMA Priority Basin Project Status
- USGS GAMA Home
- GAMA Groundwater Reports
Benefits of a Priority Basin Project
The Priority Basin Project monitors, tests and assesses water quality at multiple scales throughout the state. The project integrates data from multiple agencies into a statistically-reliable data set.
Benefits include:
- Information to help protect the source of California’s drinking water supply
- Improved comprehensive groundwater quality monitoring
- Enhanced understanding of groundwater
- Increased availability of groundwater quality information to the public
- Early warning system of potential threats to groundwater supplies
- Advanced monitoring techniques reveal emerging contaminants
