Study Boundary and Grid Cells for the Yuba and Bear Watersheds Shallow Aquifer Study Unit

The U.S. Geological Survey collected groundwater samples from 71 domestic wells and 4 springs in Nevada, Yuba, Sierra, and Placer Counties, California in 2015-2016. The wells and springs were sampled for the Yuba and Bear Watersheds Shallow Aquifer Study Unit of the California State Water Resources Control Board Groundwater Ambient Monitoring and Assessment (GAMA) Program Priority Basin Project’s assessment of the quality of groundwater resources used for domestic drinking water supply. The Yuba and Bear Shallow Aquifer Study Unit includes portions of the watersheds of the Upper Yuba (hydrologic unit code 18020125) and Upper Bear (hydrologic unit code 18020126) that are within the Sierra Nevada Province. The two study areas were divided into equal area grid cells of approximately 30 square kilometers each; one domestic well or spring was sampled per cell. The number of cells was determined by the total size of the study area, so that each study area has equally sized grid cells. The Yuba study area was divided into 47 cells and the Bear study area into 28 cells. The orientation of the cells for the Yuba study area was rotated 60 degrees from North to be approximately perpendicular with the contact between the Central Valley and Sierra Nevada provinces. Groundwater samples were analyzed for field water-quality parameters, volatile organic compounds, pesticides and pesticide degradates, nutrients, major ions and trace elements, hexavalent chromium, perchlorate, gross alpha and gross beta particle activities, noble gases, tritium, carbon-14 in dissolved inorganic carbon, stable isotopic ratios of water and dissolved nitrate, and microbial indicators. This dataset identifies the grid cells for the two targeted study areas of the Yuba and Bear Shallow Aquifer Study Unit.

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