| az_huc5_83 - 5th level (10 digit) hydrologic unit codes (hucs) | |
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Data format: ArcInfo Coverage File or table name: az_watshed_5 Coordinate system: Universal Transverse Mercator Theme keywords: HUC, Hydrologic Units, Hydrologic Unit Code, Region, Subregion, Basin, Subbasin, Watershed, Watershed Boundaries, boundaries, WBD, Watershed Boundary Dataset, HUA, Hydrologic Units Area |
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Abstract:
This data set is a complete digital hydrologic unit boundary layer to the 5th level for the State of Arizona. 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 1st through 5th levels of hydrologic units, 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. |
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Metadata elements shown with blue text are defined in the Federal Geographic Data Committee's (FGDC) Content Standard for Digital Geospatial Metadata (CSDGM). Elements shown with green text are defined in the ESRI Profile of the CSDGM. Elements shown with a green asterisk (*) will be automatically updated by ArcCatalog. ArcCatalog adds hints indicating which FGDC elements are mandatory; these are shown with gray text.
This data set is a complete digital hydrologic unit boundary layer to the 5th level for the State of Arizona. 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 1st through 5th levels of hydrologic units, 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.
The hydrologic unit boundaries provide a uniquely identified and uniform method of subdividing large drainage areas. The smaller sized watersheds are useful for numerous application programs supported by a variety of local, State, and Federal Agencies. This data set is intended to be used as a tool for water-resource management and planning activities, particularly for site-specific and localized studies requiring a level of detail provided by large-scale map information. The dataset will be appended to a larger seamless nationally consistant geospatial database as other states complete their portion of the Watershed Boundary Dataset.
Outlet methodology: Outlet points were chosen by first choosing as many full stream reaches tributaries to the main stem as possible (classic watersheds). Outlets are then attempted adjacent to these classic watersheds on the main stem. Any remaining watersheds are then chosen in accordance to the next best available option. See "Process Step" for further information.
Publication date of sources
The distributor shall not be held liable for improper or incorrect use of this data, based on the description of appropriate/inappropriate uses described in this metadata document. It is strongly recommended that this data is directly acquired from the distributor and not indirectly through other sources which may have changed the data in some way. These data should not be used at scales greater than 1:24,000 for the purpose of identifying hydrographic watershed boundary feature locations. United States Department of Agriculture-Natural Resources Conservation Service should be acknowledged as the data source in products derived from these data. The Watershed Boundary Dataset is public information and may be interpreted by all organizations, agencies, units of government, or others based on needs; however, they are responsible for the appropriate application of the data. Federal, State, or local regulatory bodies are not to reassign to the Natural Resources Conservation Service any authority for the decisions they make. The Natural Resources Conservation Service will not perform any evaluations of these maps or purposes related solely to State or local regulatory programs. Photographic or digital enlargement of these maps to scales greater than that at which they were originally delineated can result in misrepresentation of the data. If enlarged, the maps will not include the fine detail that would be appropriate for mapping at the small scale. Digital data files are periodically updated. Files are dated, and users are responsible for obtaining the latest version of the data from the source distributor.
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Funding for the Arizona Watershed Boundary Dataset (WBD) was provided by the Natural Resources Conservation Service, Forest Service, and Bureau of Land Management. Representatives from these and other organizations also contributed a substantial amount of time and salary towards quality review of the dataset.
There are no unclosed polygons, intersections without nodes, or polygons without labels or with more than one label. Arc/Info's topological correction program CLEAN was used to correct intersections without nodes, identify unclosed polygons and remove duplicate lines with the same beginning and ending nodes. All sliver and wedge polygons were removed manually in ArcEdit.
All fields for all polygons in the .pat are attributed except for HU_8_DS and HU_10_DS. These will be attributed at a later date. NCONTRB_A is only attributed if the polygon is a 100% closed area. Otherwise the NCONTRB_A field will have a 0 value, even if it is partially or even mostly non-contributing. All fields for the lines in the .aat are attributed except hu_level. This field in the .aat will attributed at a later date. The lines adjacent to the universal polygon may be attributed with a 0. These cannot be attributed until the adjacent states complete their linework at which point the highest level of hydrologic unit can be determined.
The WBD was produced using Enhanced Digital Raster Graphics (DRG-e's) digital images as source map. Data completeness for DRG files reflect content of the source graphic and may therefore be reflected in the completeness and accuracy of the WBD. The map was digitized from USGS 1:24,000-scale digital raster graphic base maps, with an inherited error of +/- 40 feet according to USGS National Map Accuracy Standards. Digitized line locations were held to the +/- 40 foot accuracy standards by ensuring that all lines were within a 12 meter buffer of where visual interpretion put the actual boundary. Any lines outside the buffer were corrected. It is estimated that the errors detected were less than 10%. It should be noted that while general rules of hydrology were used (i.e. water flows downhill), the location of boundaries is still somewhat subjective as the 1:24,000-scale DRG-e do not always provide enough information for identifying the location of the boundaries. In these instances group consensus was used. Please refer to the methods section for more details on watershed delineation rules. Unquantifiable errors may be associated with coordinate shift. The default was used for all other ArcEdit tolerances except fuzzy tolerance which was set to .05 meters, and dangle which was set to 0. As with the original DRGs, DRG-e is cast in the Universal Transverse Mercator projection and is referenced to the NAD27 datum. When the DRG-e's are used in the NAD83 datum the alternate world files only approximate the NAD83 by shifting the coordinates of the imagery. The total error introduced using this shift is less than 2 meters for all DRG-e imagery.
Source Contribution map delineation and field verify.
Process description: Level 5 (10 digit) watersheds were delineated within a nested hierarchical structure using the existing Level 4 (8 digit) watershed delineation as a starting framework. The 11-digit code was reduced to 10 digits to conform to the new Federal Standards for the Delineation of Hydrologic Units Boundaries, by dropping the zero in the last position. The typical size of a level 5 watershed is 40,000 to 250,000 acres. Only those watersheds that show some unique cultural, physical, or logical significance were included in the data. The order of precedence for establishing the outlet point of a watershed is: (1) at the outlet of a lake or pond; (2) at a confluence for a full stream reach forming classic watershed; (3) at the adjacent point to (2); (4) at some topographic feature, such as a natural gap in topography; (5) at a dam or stream gauging station.
3003 N. Central Ave., Suite 800
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Dataset copied.
Internal feature number.
ESRI
Feature geometry.
ESRI
Internal node number for the beginning of an arc (from-node).
ESRI
Internal node number for the end of an arc (to-node).
ESRI
Internal node number for the left polygon.
ESRI
Internal node number for the right polygon.
ESRI
Length of feature in internal units.
ESRI
Internal feature number.
ESRI
User-defined feature number.
ESRI
Hydrologic Unit level.
Line spatial data source.
Metadata ID number.
Internal feature number.
ESRI
Feature geometry.
ESRI
Area of feature in internal units squared.
ESRI
Perimeter of feature in internal units.
ESRI
Internal feature number.
ESRI
User-defined feature number.
ESRI
Region code (2 digit).
Subregion code (2 digit).
Basin code (2 digit).
Subbasin code (2 digit).
Watershed code (2 digit).
Region code (2 digit).
Region name.
Subregion code (4 digit).
Subregion name.
Basin code (6 digit).
Basin name.
Subbasin code (8 digit).