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  2. Hydrologic unit system (United States) - Wikipedia

    en.wikipedia.org/wiki/Hydrologic_unit_system...

    This map of United States water resource subregion hydrologic units updated boundaries to include the ocean as well as the portions of the basins that cross international borders For the use of hydrologists, ecologists, and water-resource managers in the study of surface water flows in the United States, the United States Geological Survey ...

  3. Libre Map Project - Wikipedia

    en.wikipedia.org/wiki/Libre_Map_Project

    The Libre Map Project was started by Jared Benedict and around 100 additional individuals contributing money to purchase (or "liberate") a full set of 1:24K scale USGS topographic maps in Digital raster graphic form. [1] The map files were then hosted by archive.org to ensure the map data will continue to be freely available to everyone ...

  4. The National Map - Wikipedia

    en.wikipedia.org/wiki/The_National_Map

    The USGS also utilizes data from The National Map Corps, which consists of volunteers who devote some of their time to provide cartographic information on structures. [ 4 ] The National Map is the official replacement for the USGS topographic map program .

  5. Surface water - Wikipedia

    en.wikipedia.org/wiki/Surface_water

    For USGS water-use reports, surface water is considered freshwater when it contains less than 1,000 milligrams per liter (mg/L) of dissolved solids. [2] There are three major types of surface water. Permanent (perennial) surface waters are present year round, and includes lakes, rivers and wetlands (marshes and swamps).

  6. United States Geological Survey - Wikipedia

    en.wikipedia.org/wiki/United_States_Geological...

    Georeferenced map images are available from the USGS as digital raster graphics (DRGs) in addition to digital data sets based on USGS maps, notably digital line graphs (DLGs) and digital elevation models (DEMs). In 2015, the USGS unveiled the topoView website, a new way to view their entire digitized collection of over 178,000 maps from 1884 to ...

  7. Water resource region - Wikipedia

    en.wikipedia.org/wiki/Water_Resource_Region

    A water resource region is the first level of classification used by the United States Geological Survey to divide and sub-divide the United States into successively smaller hydrologic units as part of the U.S. hydrologic unit system. This first level of classification divides the United States into 21 major geographic areas, or regions.

  8. United States Geological Survey Library - Wikipedia

    en.wikipedia.org/wiki/United_States_Geological...

    Included are historical maps and publications of USGS, as well as early publications of many federal, state and other geological surveys. Records of select geological societies are also maintained in the collection, such as the Geological Society of Washington, which was founded by John Wesley Powell and other noted scientists after the Civil ...

  9. Vadose zone - Wikipedia

    en.wikipedia.org/wiki/Vadose_zone

    Cross section showing the water table varying with surface topography as well as a perched water table The vadose zone , also termed the unsaturated zone , is the part of Earth between the land surface and the top of the phreatic zone , the position at which the groundwater (the water in the soil's pores) is at atmospheric pressure ("vadose" is ...