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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
Attributes for NHDPlus Catchments (Version 1.1) for the Conterminous United States: Hydrologic Landscape Regions
Department of the Interior —
This data set represents the area of Hydrologic Landscape Regions (HLR) compiled for every catchment of NHDPlus for the conterminous United States. The source data... -
Federal
Attributes for NHDplus Catchments (Version 1.1) for the Conterminous United States: Population Density, 2000
Department of the Interior —
This data set represents the average population density, in number of people per square kilometer multiplied by 10 for the year 2000, compiled for every catchment of...