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California Groundwater Ambient Monitoring and Assessment (GAMA) Program Priority Basin Project Study Areas and grid cells for assessment of groundwater resources used for public drinking-water supply.

Metadata Updated: October 28, 2023

The California Groundwater Ambient Monitoring and Assessment Program (GAMA) is a statewide, comprehensive assessment of groundwater quality designed to help better understand and identify risks to groundwater resources. GAMA is being implemented by the California State Water Resources Control Board. The USGS is the technical lead for the Priority Basin Project (PBP), one of the components of the GAMA Program. The initial focus of the GAMA Priority Basin Project in 2004 to 2012 was on assessment of water-quality in groundwater resources used for public drinking water supply (Belitz and others, 2003; 2015). Groundwater basins and sub-basins (472 in total) were prioritized based upon a number of factors (Belitz and others 2003). Two hundred and twenty-seven of these basins and additional areas outside of basins were subsequently grouped into 35 study units comprising 87 Study Areas. The basin and sub-basin boundaries, local geology, local knowledge, and watershed data were used to define the Study Areas. The Study Areas each were divided into equal-area grid cells collectively referred as a "study area grid". The number and size of cells generated for each Study Area was based upon the size of the area being sampled, and the number of public-supply wells available to sample. Three Study Areas contained an insufficient number of public-supply wells for division into a study area grid and were instead directly sampled. The number of cells in a study area grid ranged from 7 to 122 (median 20), and the size of the cells ranged from 4 to 471 km2 (median 25 km2). Additional information about the design of individual study area grids can be found in the reports listed below. The 87 Study Areas are collected and assembled here into one GIS dataset.

Access & Use Information

Public: This dataset is intended for public access and use. License: No license information was provided. If this work was prepared by an officer or employee of the United States government as part of that person's official duties it is considered a U.S. Government Work.

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Metadata Created Date June 1, 2023
Metadata Updated Date October 28, 2023

Metadata Source

Harvested from DOI EDI

Additional Metadata

Resource Type Dataset
Metadata Created Date June 1, 2023
Metadata Updated Date October 28, 2023
Publisher U.S. Geological Survey
Identifier USGS:5936e071e4b0f6c2d0d884c8
Data Last Modified 20200812
Category geospatial
Public Access Level public
Bureau Code 010:12
Metadata Context
Metadata Catalog ID
Schema Version
Catalog Describedby
Harvest Object Id 40b30960-a4c2-47d6-b058-189f17d4c0fc
Harvest Source Id 52bfcc16-6e15-478f-809a-b1bc76f1aeda
Harvest Source Title DOI EDI
Metadata Type geospatial
Old Spatial -124.4445,32.489,-113.7503,42.0432
Publisher Hierarchy White House > U.S. Department of the Interior > U.S. Geological Survey
Source Datajson Identifier True
Source Hash 3d55b7a3332176c300fabf04864137ea5fe5f9a6897a46490d3aa58948bc3541
Source Schema Version 1.1
Spatial {"type": "Polygon", "coordinates": -124.4445, 32.489, -124.4445, 42.0432, -113.7503, 42.0432, -113.7503, 32.489, -124.4445, 32.489}

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