Watershed boundaries for SAA Region SAA Version 3.0 Version Date: 21 March, 1996 --------------------------------------------------------------------------- ------------------------------------------------------------------------ Identification Information Data Layer Name: Watershed boundaries for SAA region at 1:100,000 scale Description: This data layer includes boundaries of the hydrologic cataloging units for hydrologic units of which a portion is in the SAA area. These HUCS were created to better fit the 1:100,000 scale RF3 stream files to allow for more asthetic display of maps based on RF3 data. This coverage is at the 1:100,000 scale only in that it 'fits' the stream data. These hydrologic units are not intended to be used as a 1:100,000 scale watershed map. This data layer also includes hydrologic unit codes, hydrologic unit names, and acres per unit. Keywords: watershed, hydrologic units, hydrologic unit codes, HUC, hydrology, drainage basin Citation: none Native Data Set Environment: Unix; Arc/Info 7.1 pathname: //watershd.e00.Z Scale: 1:2,500,000 File Format: The data layer is in one Arc/Info polygon coverage and is available in compressed Arc/Info export format. Use Restrictions: none Access Restrictions: none ------------------------------------------------------------------------ -------------------------------------------------------------------- Spatial Reference Information Datum: North American Datum 1983 (NAD83) Precision: single Projection: Albers Equal Area Units: meters Spheroid: WGS-84 1st Std Parallel: 34 00 00 2nd Std Parallel: 38 00 00 Central Meridian: -82 00 00 Origin: 33 00 00 False Northing: 0.0 False Easting: 0.0 Extent: West Bounding Coord.: East Bounding Coord.: North Bounding Coord.: South Bounding Coord.: Distance Resolution: Vertical Resolution: n/a -------------------------------------------------------------------- --------------------------------------------------------------------------- Data Quality Information Thematic Accuracy: unknown Confidence: unknown Accuracy Method: Horizontal Accuracy: unknown Confidence: unknown Accuracy Method: unknown Vertical Accuracy: n/a Logical Consistency: Completeness: --------------------------------------------------------------------------- -------------------------------------------------------------------------- Source Information Source Material: Digitized Hydrologic Units for the United States at a scale of 1:2,500,000. Organization: U.S.G.S. Date: 1985 Distance Resolution: unknown Contribution: Hydrologic unit boundaries and codes Source Material: Codes for the Identification of hydrologic units in the United States and the Caribbean outlying areas. Organization: U.S.G.S. Date: 1982 Distance Resolution: n/a Contribution: Hydrologic unit coding scheme description Source Material: Hydrologic Unit Map of the United States: scale 1:2,500,000; 2 sheets. Organization: U.S.G.S. Date: 1980 Distance Resolution: unknown Contribution: Original source document for digitized hydrologic unit map See Volume 2 for more information. -------------------------------------------------------------------------- ----------------------------------------------------------------------- Processing History Information Process Description: 1. Hydrologic units were compiled and published on a 2-piece 1:2,500,000 scale map of the United States. 2. The 2-piece hydrologic unit map was digitized in 76 page-size sections which were photocopied from the original map. Each digitized section was checked for coding and topological errors which were corrected. The sections were merged into one file. 3. Using Arc/Info software (GRID) the stream arcs from the EPA RF3 coverage were gridded based on what hydrologic unit code was stored in the attribute file (.aat). These grid cells were then 'grown' out until all cells were assigned a hydrologic unit code. These cells were then transformed into polygons using the GRIDPOLY command in Arc/Info. These polygons were then compared to the original 1:2,000,000 scale HUCs and areas where significant differances occured were updated to better 'fit' the stream data. ----------------------------------------------------------------------- --------------------------------------------------------------------- Entity/Attribute Information Entity: WATERSHD.PAT Definition: Watershed Polygons Attributes: COL ITEM NAME WDTH OPUT TYP N.DEC DEFINITION 1 AREA 4 12 F 3 Area in square meters per polygon 5 PERIMETER 4 12 F 3 Perimeter in meters per polygon 9 WATERSHD# 4 5 B - Internal polygon identification number 13 WATERSHD-ID 4 5 B - User-defined polygon identification number 17 HUC 8 8 I - Hydrologic unit cataloging code (integer format) 25 NAME 60 60 C - Hydrologic unit catalog name 85 ACRES 8 8 F 2 Number of acres per cataloging unit (calculated from Area) 93 HUC8 8 8 C - Hydrologic unit cataloging code (character format) ** REDEFINED ITEMS ** 17 HUC2 2 2 I - Hydrologic unit region code 17 HUC4 4 4 I - Hydrologic unit subregion code 17 HUC6 6 6 I - Hydrologic unit accounting code See Volume 2 for information about the hydrologic unit coding scheme (region, subregion, accounting, and cataloging unit codes). Entity: WATERSHD.AAT Definition: Watershed Boundary Lines Attributes: COL ITEM NAME WDTH OPUT TYP N.DEC DEFINITION 1 FNODE# 4 5 B - Internal ID number of beginning node of arc 5 TNODE# 4 5 B - Internal ID number of ending node of arc 9 LPOLY# 4 5 B - Internal ID number of polygon on left side of arc 13 RPOLY# 4 5 B - Internal ID number of polygon on right side of arc 17 LENGTH 4 12 F 3 Length of arc in meters 21 WATERSHD# 4 5 B - Internal arc identification number 25 WATERSHD-ID 4 5 B - User-defined arc identification numb 29 BNDTYPE 2 2 I - Boundary type code to identify boundaries types between hydrologic units See Volume 2 for more information on BNDTYPE. Entity: WATERSHD.TIC Definition: Watershed Boundary Coverage Control Tics Attributes: COL ITEM NAME WDTH OPUT TYP N.DEC DEFINITION 1 IDTIC 4 5 B - User-defined tic identification number 5 XTIC 4 12 F 3 X coordinate for tic 9 YTIC 4 12 F 3 Y coordinate for tic Entity: hucs100k.BND Definition: Watershed Boundary Coverage Bounding Coordinates Attributes: COL ITEM NAME WDTH OPUT TYP N.DEC DEFINITION 1 XMIN 4 12 F 3 Minimum x-coordinate in coverage 5 YMIN 4 12 F 3 Minimum y-coordinate in coverage 9 XMAX 4 12 F 3 Maximum x-coordinate in coverage 13 YMAX 4 12 F 3 Maximum y-coordinate in coverage --------------------------------------------------------------------- ------------------------------- Status Information Data Set Status: Available Release Date: ------------------------------- ----------------------------------------- Metadata Reference Information Date: March 21, 1996 Review Date: March 21, 1996 Contact: Dennis H. Yankee ----------------------------------------- ---------------------------------------------------------- Distribution Information Distribution Contact: Distribution Liability: File Compression Technique: UNIX compress, Arc/Info export format Transfer Size: -------------------------------------------------- -------------------------------------------------- Contact Information Contact Person: Dennis H. Yankee Contact Mail Address: Tennessee Valley Authority Contact Phone: (423)632-1541 Contact Fax: (423)632-1612 Contact email: dyankee@mhs-tva.attmail.com -------------------------------------------------