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  2. Hydrologic unit system (United States) - Wikipedia

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

    [1] [2] Over time the system was changed and expanded. [3] As of 2010 there are six levels in the hierarchy, represented by hydrologic unit codes from 2 to 12 digits long, called regions, subregions, basins, subbasins, watersheds, and subwatersheds. The table below describes the system's hydrologic unit levels and their characteristics, along ...

  3. United States Geological Survey - Wikipedia

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

    [30] [31] In recent years, budget constraints have forced the USGS to rely on donations of time by civilian volunteers in an attempt to update its 7.5-minute topographic map series, and USGS stated outright in 2000 that the program was to be phased out in favor of The National Map [32] (not to be confused with the National Atlas of the United ...

  4. List of river basins in the United States - Wikipedia

    en.wikipedia.org/wiki/List_of_river_basins_in...

    Map of major river basins. These are the major U.S. river basins in the U.S., as designated by the U.S. Water Resources Council. [1] Each of these river basins contain a number of smaller river basins.

  5. The National Map - Wikipedia

    en.wikipedia.org/wiki/The_National_Map

    The National Map Corps consists of volunteers who devote some of their time to provide cartographic information to the U.S. Geological Survey. The only requirements to participate are having access to the Internet and a current familiarity with the area being mapped. [6] This data is used to update The National Map.

  6. List of rivers of the United States by discharge - Wikipedia

    en.wikipedia.org/wiki/List_of_rivers_of_the...

    This is a list of rivers in the continental United States by average discharge (streamflow) in cubic feet per second. All rivers with average discharge more than 15,000 cubic feet per second are listed.

  7. USGS DEM - Wikipedia

    en.wikipedia.org/wiki/USGS_DEM

    The USGS DEM format is a self-contained (single file) set of ASCII-encoded (text) 1024-byte (1024 ASCII chars) blocks that fall into three record categories called A, B, and C. There is no cross-platform ambiguity since line ending control codes are not used, and all data including numbers is represented in readable text form.

  8. Water level - Wikipedia

    en.wikipedia.org/wiki/Water_level

    Water level, also known as gauge height or stage, is the elevation of the free surface of a sea, stream, lake or reservoir relative to a specified vertical datum. [1]

  9. 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 ...