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Federal
USGS Water-Quality Data for the Nation - National Water Information System (NWIS)
Department of the Interior —
The USGS compiles online access to water-resources data collected at approximately 1.5 million sites in all 50 States, the District of Columbia, Puerto Rico, the... -
Federal
Map of Arsenic concentrations in groundwater of the United States
Department of the Interior —
The map graphic image at https://water.usgs.gov/GIS/browse/arsenic_map.png illustrates arsenic values, in micrograms per liter, for groundwater samples from about... -
Federal
Tillage Practices in the Conterminous United States, 1989-2004--Datasets Aggregated by Watershed; tillage_lu92e
Department of the Interior —
This dataset is an aggregation of county-level tillage practices to the 8-digit hydrologic unit watershed. The original county-level data were collected by the... -
Federal
Base-flow index grid for the conterminous United States
Department of the Interior —
This 1-kilometer raster (grid) dataset for the conterminous United States was created by i nterpolating base-flow index (BFI) values estimated at U.S. Geological...