Description: 4-Digit Watershed Boundary Data. Hydrologic Unit delineation are closed polygons that encompass all area draining toward the lowest point (called outlet or pour point) in the polygon. Because of varying sizes for the different hydrologic unit levels: some polygons do not include all areas up to the drainage divide, but all areas are included up to one or more other upstream hydrologic units. A unique hydrologic unit code is used to identify each hydrologic unit. The hydrologic unit codes start with the 2-digit Region number that contains the 4-, 6-, and 8-digit hydrologic units. Each hydrologic unit has a unique hydrologic code.
Definition Expression: N/A
Copyright Text: USDA/NRCS - National Cartography & Geospatial Center
Description: 8-Digit Watershed Boundary Data. Hydrologic Unit delineation are closed polygons that encompass all area draining toward the lowest point (called outlet or pour point) in the polygon. Because of varying sizes for the different hydrologic unit levels: some polygons do not include all areas up to the drainage divide, but all areas are included up to one or more other upstream hydrologic units. A unique hydrologic unit code is used to identify each hydrologic unit. The hydrologic unit codes start with the 2-digit Region number that contains the 4-, 6-, and 8-digit hydrologic units. Each hydrologic unit has a unique hydrologic code.
Definition Expression: N/A
Copyright Text: USDA/NRCS - National Cartography & Geospatial Center
Description: This data set is a complete digital hydrologic unit boundary layer to the Subwatershed (12-digit) 6th level for the entire United States. This data set consists of geo-referenced digital data and associated attributes created in accordance with the "FGDC Proposal, Version 1.0 - Federal Standards For Delineation of Hydrologic Unit Boundaries 3/01/02"(http://www.ftw.nrcs.usda.gov/huc_data.html). Polygons are attributed with hydrologic unit codes for 4th level sub-basins, 5th level watersheds, 6th level subwatersheds, name, size, downstream hydrologic unit, type of watershed, non-contributing areas and flow modification. Arcs are attributed with the highest hydrologic unit code for each watershed, linesource and a metadata reference file.
Definition Expression: N/A
Copyright Text: Natural Resources Conservation Service (NRCS)
Description: Delta boundary version 2002.4. Delineates the legal Delta established under the Delta Protection Act (Section 12220 of the Water Code) passed in 1959. This boundary file has been reviewed by a variety of relevant professionals and is considered to be accurate. The exact accuracy is somewhat uncertain, but can be considered acceptable for mapping at 1:24000.
The original topographic maps containing the drawn delta border were scanned from the Department of Water Resources. Images were registered to 1:24,000 USGS DRG's in ArcView (ESRI) utilizing imagewarp extension. The Delta boundary was digitized from the registered images. Accuracy within acceptable 7.5 Minute USGS map accuracy standards (1:24000 scale).
The original legal boundary maps obtained from the Delta Protection Commission were compiled by DWR Land & Right of Way sometime in the early 1980's. They were based from the legal description in section 12220 of the Water Code, with ambiguities in the Code addressed by the individuals involved in the mapping project at that time. One revision was made to the original maps in the vicinity of Point Pleasant, and is the only difference between this and the 4.2001 version of the legal Delta boundary Arc/INFO coverage.
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Copyright Text: Chico State University, California DWR.