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The California Groundwater Ambient Monitoring and Assessment Program (GAMA) is a statewide assessment of groundwater quality designed to help better understand and identify risks to groundwater resources. GAMA is implemented by the California State Water Resources Control Board. The U.S. Geological Survey (USGS) is the technical lead for the Priority Basin Project (PBP), one of the components of the GAMA Program. Starting in 2012, GAMA began an assessment of water resources in shallow aquifers in California. These shallow aquifers provide water for domestic and small community-supply wells, which are often drilled to shallower depths in the groundwater system than public-supply wells. Shallow aquifers are of interest because shallow groundwater may respond more quickly and be more susceptible to contamination from human activities at the land surface, than the deeper aquifers (USGS, 2018). To prioritize shallow aquifers, California was divided into 938 groundwater units consisting of California Department of Water Resources (DWR) groundwater basins and highland areas outside of the basins defined by California Groundwater Units (Johnson and Belitz, 2014) or Hydrologic Units (HUC8) from the Watershed Boundary Dataset (USGS and USDA, 2013). The groundwater units were prioritized for sampling based on the number and density of households relying on domestic wells, water-use, and well-location information compiled from well-completion reports submitted to the DWR. The groundwater units were grouped into study units designed to facilitate comparison of groundwater quality between the shallow aquifer systems and the deep aquifer systems assessed by GAMA from 2004 to 2012 (Bennett, 2018). The study units (and study areas when applicable) were divided into equal area polygons (cells) so that all cells within a given study unit (or study area) have an equal area. These grid cells can be found in the GAMA_PBP_SAA_GridCells shapefile included in this Data Release.

A two-dimensional, groundwater flow model (VS2DI) was developed to examine groundwater flow near wetlands in the Prairie Pothole Region of North Dakota. Four model domains were created, the first three are hypothetical or idealized and do not relate to an actual location. The fourth domain is a cross section designed to replicate results presented in Winter and Carr (https://pubs.er.usgs.gov/publication/wri8099). The model was used to evaluate conditions suitable for groundwater to flow from a wetland to another body of water. This USGS data release contains all of the input and output files for the simulations described in the associated journal article (https://doi.org/10.1007/s13157-017-0956-7). This data release also includes the VS2DI v1.3 source code.

The following dataset has been developed to assist the Groundwater Sustainability Agencies (GSAs) in their water budget development per the Groundwater Sustainability Plan Regulations §354.18. GSAs may choose to use this dataset but are not required. GSAs have the option to develop their own water year types based on best available data. For information on how the SGMA Water Year Type Dataset was developed, please see the SGMA Water Year Type Dataset Development Report. Questions or comments can be directed to the Sustainable Groundwater Management Office at sgmps@water.ca.gov.

GP_betasdam Final data and code. This dataset is associated with the following publication: Eddy, M., S. Gross, K. Fritz, B. Topping, T. Nadeau, R. Edgerton, and J. Kelso. Data Supplement to Development and Evaluation of the Beta Streamflow Duration Assessment Method (SDAM) for the Great Plains (GP). U.S. Environmental Protection Agency, Washington, DC, USA, 2022.

GP_betasdam Final data and code. This dataset is associated with the following publication: Eddy, M., S. Gross, K. Fritz, B. Topping, T. Nadeau, R. Edgerton, and J. Kelso. Data Supplement to Development and Evaluation of the Beta Streamflow Duration Assessment Method (SDAM) for the Great Plains (GP). U.S. Environmental Protection Agency, Washington, DC, USA, 2022.