U.S. Geological Survey 2004 1.0 vector digital data Reston, VA U.S. Geological Survey http://water.usgs.gov/lookup/getspatial?nasqan2k A digital representation of the watersheds of 43 sites on large river systems sampled by the National Stream Quality Accounting Network (NASQAN) of the U. S. Geological Survey (USGS) in 2000 was created primarily from 1:250,000 hydrologic units(HUCs) in the United States. Watershed information from Canada and Mexico was incorporated to complete the areas draining to the sampling sites from outside the United States. The sampled rivers are in one of four major river systems: the Mississippi, the Colorado, the Rio Grande, or the Columbia. Digital watersheds are required to analyze natural and anthropogenic influences on water quality at the sampling sites. The native format for these data is an ArcInfo coverage that contains 4 region feature classes. These feature classes allow water quality or ancillary data, such as land use or pesticide application, to be summarized for each NASQAN sampling site: (1) by the entire watershed including areas outside the US, (2) by the portion of the watershed in the U.S.,(3) by the intervening areas between the sampling sites including areas outside the US, or (4) by the intervening areas only within the U.S. Shape files created from these Arc Info region features include both individual watersheds above each sampling site and a single shape file (nas_sect.shp) of polygons representing the intervening drainage areas between all the sampling sites. A companion data set of the sampling sites (nas2000) as 43 points is available along with the boundaries. Watersheds are included for the following sampling sites at USGS gages. Site list: ID NAME MISSISSIPPI 03216600 Ohio River at Greenup Dam near Greenup, KY 03303280 Ohio River at Cannelton Dam at Cannelton, IN 03378500 Wabash River at New Harmony, IN 03609750 Tennessee River at Highway 60 near Paducah, KY 03612500 Ohio River at Dam 53 near Grand Chain, IL 05330000 Minnesota River near Jordan, MN 05331580 Mississippi River below Lock and Dam 2 at Hastings, MN 05420500 Mississippi River at Clinton, IA 05587455 Mississippi River below Grafton, IL 06185500 Missouri River near Culbertson MT 06329500 Yellowstone River near Sidney MT 06338490 Missouri River at Garrison Dam, ND 06440000 Missouri River at Pierre SD 06610000 Missouri River at Omaha, NE 06805500 Platte River at Louisville, NE 06934500 Missouri River at Hermann, MO 07022000 Mississippi River at Thebes, IL 07263620 Arkansas R. at David D. Terry Lock and Dam below Little Rock, AR 07373420 Mississippi River near St. Francisville, LA 07381495 Atchafalaya River at Melville, LA RIO GRANDE 08364000 Rio Grande at El Paso, TX 08374200 Rio Grande below Rio Conchos nr Presidio, TX 08377200 Rio Grande at Foster Ranch, near Langtry, TX 08447410 Pecos River near Langtry, TX 08450900 Rio Grande below Amistad Reservoir near Del Rio, TX 08459200 Rio Grande at Pipeline Crossing below Laredo TX 08461300 Rio Grande below Falcon Dam TX 08470400 Arroyo Colorado at Harlingen TX 08475000 Rio Grande near Brownsville TX COLORADO 09180500 Colorado River near Cisco UT 09315000 Green River at Green River UT 09379500 San Juan River at Bluff UT 09380000 Colorado River at Lees Ferry AZ 09404200 Colorado River above Diamond Creek near Peach Springs AZ 09421500 Colorado River below Hoover Dam AZ-NV 09429490 Colorado River above Imperial Dam CA-AZ 09522000 Colorado River at Northerly International Boundary (NIB), above Morelos Dam, near Andrade, CA COLUMBIA 12400520 Columbia River at Northport WA 12472900 Columbia River at Vernita Bridge near Priest Rapids Dam WA 13353200 Snake River at Burbank WA 14128910 Columbia River at Warrendale OR 14211720 Willamette River at Portland OR 14246900 Columbia River at Beaver Army Terminal near Quincy OR These watersheds represent only the contributing area; that is, HUCs that could be determined to be closed basins are excluded. See the Data Quality section for procedures used. Drainage areas (DA) computed from this data set may differ from the drainage area published for the gage from the USGS NWIS database. Site information for some, but not all, USGS gages are published on the web. The following sites have site information including drainage areas at http://waterdata.usgs.gov/ga/nwis/nwis (accessed 7/1/3). The last column in this table is the difference in percent between the GIS contributing drainage area and the published drainage area (or contributing drainage area where available). There are significant differences in calculated watershed area for only two rivers: the Platte (gage 06805500) and the Pecos (gage 08447410). (The percent difference listed for the Rio Grande (gage 08549200) reflects the effect of its tributary, the Pecos River.) ID GIS-Contributing NWIS-web NWIS-web Percent drainage area(DA) total DA contributing DA difference 03216600 61,531 62,000 - -1 03303280 96,432 97,000 - -1 05330000 16,180 16,200 - 0 05331580 37,041 37,100 - 0 05420500 85,778 85,600 85,600 0 06185500 92,484 91,557 - 1 06329500 69,078 69,103 - 0 06338490 180,084 181,400 81,400 -1 06440000 239,369 243,500 - -2 06610000 314,254 326,759 22,800 -3 06805500 85,487 85,370 71,000 20 06934500 512,811 524,200 - -2 07022000 703,777 713,200 - -1 08447410 44,174 35,179 - 26 08459200 156,359 132,578 - 18 09180500 23,971 24,100 - -1 09315000 40,644 44,850 40,590 0 09379500 22,993 23,000 - 0 09380000 108,136 111,800 - -3 09404200 145,602 149,316 44,660 1 09421500 166,917 171,700 - -3 09429490 181,535 188,500 84,500 -2 12400520 60,373 60,200 - 0 12472900 96,333 96,000 - 0 13353200 102,344 108,800 - 0 14128910 236,622 240,400 - 0 14211720 11,196 11,100 - -1 14246900 253,193 256,900 - -1 Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government. Although this Federal Geographic Data Committee-compliant metadata file is intended to document the data set in nonproprietary form, as well as in Arc/INFO format, this metadata file may include some Arc/INFO-specific terminology. 2004 publication date Complete None planned -126.968527 -74.347544 54.743707 22.728494 None water quality watersheds drainage area water-quality sampling site major rivers inlandWaters None North America United States Canada Mexico Mississippi River Columbia River Colorado River Rio Grande River There are no access restraints for this dataset. Acknowledgement of the USGS would be appreciated. There are no use constraints, but this dataset was created to be used on a regional or national scale. U.S. Geological Survey Evelyn H Hopkins Geographer mailing and physical address

Peachtree Business Center

3039 Amwiler Rd, suite 130

Atlanta GA 30360-2824 USA 1-888-275-8747 (770) 903-9199 ehopkins@usgs.gov 9:00 - 5:00 ET http://water.usgs.gov/GIS/browse/nasqan2k.gif Illlustration of data set GIF U. S. Geological Survey Microsoft Windows 2000 Version 5.1 (Build 2600) Service Pack 1; ESRI ArcCatalog 8.3.0.800 Most of the attributes for the polygons and regions are either character or numeric names and should be correct. The 2 attributes describing square miles are derived by converting the GIS area to square miles. Far more precision is implied by these numbers than is appropriate for regional data. The coverage contains region features representing the watershed boundaries for 43 NASQAN gages active in water year 2000 (10/01/99 - 09/30/01) that were modified from the 1:250,000 HUC boundaries for the continental United States. Areas outside the USA are the best that were available at the time from Canadian, Mexican, and international agencies. Digital data from Mexico was checked against commercial paper maps to help determine which watersheds drained to the USA. Data for both Mexico and Canada were also compared against earlier undocumented digital data of NASQAN drainage areas. HUCs at the national borders were not modified unless there was some available information about the neighboring country's drainage. Polygon and chain-node topology are present for polygons and lines. All polygons are labeled and were tested using Arc/INFO command labelerrors. All polygons were checked for closure and intersections by using the Arc/INFO intersecterr. Region features default to 'Composite object' in the Spatial_Data_Reference_Method, but have been change to 'GT-polygon composed of rings' in order to meet the requirements of the metadata parser, MP. The drainage area for station 09522000 on the Colorado River excludes huc 15030107 because overland flow to the Colorado is intercepted on both sides by canals. The boundary of this drainage area follows the Mexico-United States border due to lack of information. Horizontal accuracy was checked initially against the RF1 at 1:500,000 and Hydrology at 1:2,000,000 datasets. There are occasional headwaters that extend beyond the watershed boundaries. Changes were not made based on this information because it is not clear which data are more accurate. Generally the watersheds and the hydrology worked together very well. In June 2002 National Hydrography Data (1:100,000), Digital Elevation Data (roughly 1:24,000), and Digital Raster Data (1:24,000 USGS "topo" quadrangles) all became available. Some adjustments to watersheds such as the inclusion or exclusion of areas near the gage were done using this digital data and each watershed was checked for accuracy. No changes were made to the initial 1:250,000 hydrologic unit boundaries except to split them at the gages. not applicable Steeves, Peter Nebert, Douglas 1994 1 Series_Name Open-file Reston, Virginia U.S. Geological Survey 250000 digital file 2000 publication date HUC250 Provide the digital basis for the delineation of the NASQAN watersheds Seaber, Paul Kapinos, F. Paul Knapp, George L. 1987 2nd printing 1994 map Water-Supply Paper 2294 unknown U.S. Government Printing Office 500000 Water Supply Paper 1970's publication date HUM Initial authority for inclusion of 8-digit hucs in watershed. Her Majesty the Queen in Right of Canada, Natural Resources Canada 1997 atlas unknown atlasinfo@ccrs.nrcan.gc.ca 2000000 CD-ROM 1989 1992 publication date CA-cd Watershed boundaries and rivers for Canada. CONABIO Unknown vector digital data Mexico CONABIO CONOBIO apparently is a consortium of Mexican agencies working on biodiversity. Miguel Pavon of the Borderlands Information center in Austin, TX was especially helpful in providing these data from CONABIO and general assistance. He also provided hypsography (elevation contours), populated places, states, very limited rivers, and some land use. digital files unknown publication date MP These watersheds are the digital source for the areas of Mexico draining to the United States. The codes and names are in Spanish. The codes do not appear to contain information on receiving waters. The names are feature names. Longsworth, Steve Hebert, Larry Unpublished Material Steve Longsworth of the Arizona district office provided local knowledge about flow from Mexico into the Santa Cruz and San Pedro rivers in the Colorado watershed. Larry Hebert of the Utah district provided information about tributary flow into the Green River to help determine the watershed above gage 09315000 on the Green. oral communication 2001 ground condition technicians Assistance with watershed delineation Durall, Roger Unpublished Material vector digital data Roger Durall digitized streams from some paper maps of unknown origin for a local project. 24000 digital files unknown publication date rad These rivers were helpful when used with the very sparse river data set from Mexico in determining which watersheds drained to the USA and particularly in determining how to split the Mexican watersheds at the gages on the Rio Grande. GUIA ROJI, S.A. de C.V 1997 ISBN970-621-116-0 2nd edition Mexico GUIA ROJI, S.A. de C.V paper unknown publication date GUIA 1997 Assistance with determining which watersheds drain to USA. Instituto Nacional de Estadistica 1976 1000000 paper unknown publication date MX NE Assistance with determining which watersheds drain to USA. Ibarra, Solomon Huerta Dist. de Edic. Independencia Mayoreo y Menudeo Unknown Serie Mapas de Mexico 27 Mexico Dist.de Edic. Independencia Mayoreo y Menudeo 1000000 paper unknown publication date Tam Assistance with determining which watersheds drain to Rio Grande near mouth. DETENAL (direccion general de estudios del territorio nacional) 1978 1000000 paper 1978 publication date MX North This was the most used paper source in determining watersheds draining to the Rio Grande from Mexico. DeLorme Mapping 1997 ISBN 0-89933-202-1 first edition, 3rd printing paper unknown publication date Ariz Assistance in determining which watersheds drained to the Colorado River in the USA. U.S. Geological Survey 1998 vector digital data Reston. Va. U.S. Geological Survey http://water.usgs.gov/lookup/getspatial?erf1 500000 online unknown publication date RF1 Helped verify inclusion of hucs in a watershed by visual examination on-screen. Also a check that no gross errors are present in the individual hucs. Lanfear, K.J. 1998 Reston, Va. U.S Geological Survey http://water.usgs.gov/lookup/getspatial?stream 2000000 online unknown publication date stm2m Helped verify inclusion of hucs in a watershed by visual examination on-screen. Also a check that no gross errors are present in the individual hucs. U. S. Geological Survey 200208 vector digital data http://gisdata.usgs.net/ 100000 internet mapping 2003 publication date NHD Recent availability of this data allowed the watersheds to be checked against the best current representation of hydrographic features. Several watersheds were adjusted at the gages to reflect this new data source. U.S. Geological Survey 200208 http://gisdata.usgs.net/ 24000 approximately (30-meter cells) internet mapping 2003 publication date DEM Assisted in checking watersheds for final accuracy and visualized the direction of flow. U.S. Geological Survey 2001 24,000 CD-ROM unknown publication date DRG Watershed boundaries that had been added to split existing hucs at each gage were checked using the 1:24,000 digital version of the USGS 'topo' maps. the watershed boundaries were modified if necessary. This was an awkward procedure that was not feasible if the new watershed boundaries extended over many 1;24,000 quad sheets. U.S. Geological Survey Unpublished Material tabular digital data Included with coverage, Nasqan2k, as Info file. 2000000 online 1998 publication date huc2m.trace Digital file used to determine which HUCs were excluded from a watershed because surface water did not leave the area. International Boundary and Water Commission United States and Mexico 1985 Water Bulletin Number 55 10000000 paper 1985 publication date IBWC This is a page-sized paper map from a 1985 publication that shows watersheds and closed basins for the Rio Grande River. All watersheds included in the final dataset for NASQAN were compared to this map. The map shows closed basins, including a large one in the Rio Conchos, that could not be corroborated by other sources and were not noted as closed in this NASQAN watershed data. Lu L. Tan 1997 raster digital data Open-File Report 97--354 not given U.S. Geological Survey This is a CD_Rom. It might be available from the Texas District office of the USGS. 8027 Exchange Drive Austin, TX 78754-4733 (512)927-3500 FAX (512)927-3590 250000 CD-ROM 1997 publication date TX-dem Provided hillshade visualization to help determine watershed boundaries, includinpossible closed basins for the Rio Grande The major task in creating watershed boundaries for large rivers from a national data set of hydrologic units is developing a system for selecting all hucs upstream from a given point. Norman Bliss and Bruce Worstell at the USGS Eros Data Center (EDC) were experimenting with a program to tag 8-digit hucs in the Mississippi basin with their upstream and downstream relationships. They provided an undocumented coverage of 1:250,000 hucs in which some of the hucs had this preliminary coding. The dataset included regions for every huc and its upstream hucs. Their work should be considered a preliminary process in the creation of the NASQAN watersheds. HUC250 1999 Bruce Worstell USGS Eros Data Center mailing and physical address

EROS Data Center

Sioux Falls SD 57198 USA 1-888-275-8747 worstell@usgs.gov The first NASQAN process step was to make a region feature class of watersheds for NASQAN stations from hucs in the continental U.S. Watersheds for gages on the Mississippi River system were completed first. The codes added to the hydrologic unit data by the Eros Data Center (EDC) were used to assist with this process. Regions within the U.S. were then created for gages in the Columbia, Rio Grande, and Colorado river systems. The preliminary regions provided by EDC were then deleted to reduce data size. The new regions were verified by plotting with 1:2,000,000 streams. The publication, Hydrologic Unit Maps, was the initial arbiter of which hucs were included in a watershed as contributing areas. This work was being done with new software, including some beta versions of ArcGIS. This learning curve plus some software bugs occasionally resulted in data being lost and then recreated. Not all intermediate data sets still exist. HUM RF1 stm2m HUC250 2000 Evelyn Hopkins USGS Geographer mailing and physical address

3039 Amwiler Rd, suite 130

Atlanta GA 30360 USA 1-888-275-8747 Watersheds in Canada added. Canadian data was projected from Lambert to Albers. Watersheds for the Missouri and Columbia River systems were identified and added to the polygon feature class. The polygons were then added to the region features classes region.gage_na and region.sect_na. Slivers were cleaned up. Item huc250 in the polygon attribute table was set to 0. CA-cd 2000 Watersheds in Mexico added. An image file of a map of the watersheds of the Rio Grande was created by Cecelio Martinez, USGS, San Antonio, Texas from 1985 map from the International Boundary and Water Commission. This map was rectified to the best possible fit with existing digital data and used as one of the sources. Digital elevation data for the Rio Grande as hillshades were obtained from Topographic Data Sets for Texas by River Basin. Watershed data from Mexico is difficult to find and most information is in a technical Mexican Spanish that available U.S. Spanish speakers can not translate. Watersheds provided by the Borderlands Information Center in Austin, TX were projected from Decimal Degrees and converted from shape file to coverage format. Because digital hydrographic data was so sparse extensive use was made of commercial paper maps of the area to select areas in this very arid landscape that probably drain to the Colorado in the U.S. and the Rio Grande on the border. MP rad MX North GUIA 1997 MX NE Tam IBWC TX-dem 2001 Three new region classes added. Region.gage_na included the areas in Canada and Mexico for the complete, nested watersheds for each gage. New region classes, sect_usa and sect_na, were added for intervening areas between gages in order to facilitate analysis of changes in water quality between sampling sites on the same river system and natural and anthropogenic processes on intervening lands. The region features were created from the 8-digit HUCs using the gage point data, RF1 streams, 1:2,000,000 streams, and the full watershed region previously created. ArcMap Editor was used to aggregate these hydrologic units into a new feature. HUM RF1 stm2m HUC250 2000 Splitting polygon hucs at the gage was done to further refine the watershed at each gage. The new boundaries were drawn on-screen using available river datasets as guides. These new arcs probably are much less accurate than the HUC data that provides most of the boundary for each watershed. The possibility of using on-line Digital Raster Graphics (DRGs) was investigated but was not feasible at the time. technicians http://water.usgs.gov/nasqan RF1 2001 Watershed boundaries from the USGS NASQAN sampling sites upstream to the nearest HUC were further defined using 30-meter elevation data (DEMS). Because the ArcInfo region data structure is unstable when edited, a simple polygon coverage without the region feature classes was edited in ArcMap to take advantage of the program's excellent data display. The coverage that included the region features was edited in the older ArcEdit program using the simple edited coverage as a guide. DEM 200201 In June 2002 National Hydrography Data (1:100,000), Digital Elevation Data (roughly 1:24,000), and Digital Raster Data (1:24,000 USGS "topo" quadrangles) all became available. Some adjustments to watersheds such as the inclusion or exclusion of areas near the gage was done using this digital data and each watershed was checked for accuracy. 200206 Final adjustments were made to region features by appending and removing polygons. Feature class sect_na was corrupted. Dropfeature and Get commands were used to replace sect_na with a feature class from a older coverage. Duplicate labels that had resulted from the Get process were deleted using aml programming with Cursors. All attributes checked for accuracy and consistency. Metadata updated. 200208 Two watersheds that were sampled by the USGS NAWQA program were added to the coverage . USGS gage sites, 05330000 and 05331580, were also sampled by NASQAN. 2001 Coverage and shape files sent to USGS reviewers. 20020828 Reveiws received from USGS reviewers. One reviewer's main concern was that not all known closed basins had been removed from the regions that represented the station watersheds. He also noted that the USGS NWIS database was so inconsistent in its presentation of drainage areas that it could not be considered a reliable source to check drainage areas. He suggested using an info file named huc2m.trace that had been created in connection with the huc2m coverage distributed by USGS and listed the 8-digit HUCs that were closed basins. At one time this file was distributed with the coverage, but it is not currently being distributed with the HUC2m data on the USGS National Atlas. http://www-atlas.usgs.gov/atlasvue.html (accessed 3/6/3). Second reviewer made some suggestions for metadata and also that the number of shape files could be reduced by eliminating the ones clipped to US borders. 200303 Additional HUCs were removed from the 4 regions, using the huc2m.trace info file as the final authority. The Hydrologic Unit Maps publication by Seaber and others, shaded relief, and NHD were checked for each huc. The following are HUCs that are excluded from the NASQAN watersheds followed by a list of affected NASQAN siteids. Mississippi River basin 10050003 Wild Horse Lake only shows lake @ 1 million scale. Might flow north to Canada no info available from Alberta hydrology. Seaber listed as closed. Looked at Canada coverage for sect_na and gage_na. Conclusion: There is not enough information to change drainage areas in Canada. 6185500 6338490 6440000 6610000 6934500 7022000 7373420 10060007 on ND-MT border no streams at all. Hillshade inconclusive; closed in Seaber 6185500 6338490 6440000 6610000 6934500 7022000 7373420 10130106 West Missouri Coteau, ND, SD just small lakes 6440000 10160007 East Missouri Coteau ND, SD NHD does have a stream extend into this HUC, but I don't see hillshade evidence of a stream. 10160010 North Big Sioux Coteau, SD 10170201 Middle Big Sioux Coteau, SD 10170103 Lower Big Sioux, IA 6610000 6934500 7022000 7373420 11030002 Whitewoman; Seaber closed 11040005 Bear Creek; Seaber closed 7263620 7373420 Rio Grande River basin 13020206 North Plains, NM; Seaber closed 13020210 Jornada Del Muerto, NM; Seaber closed 13020208 Plains of San Agustin, NM; Seaber closed 13030103 Jornada Draw, NM; Seaber closed 8364000 8374200 8377200 8450900 8459200 8461300 8475000 These were already excluded based on Seaber 13050001 Western Estancia, NM 13050002 Eastern Estancia, NM 13050003 Tularosa Valley, NM, TX 13050004 Salt Basin, NM,TX These were excluded, are listed by Seaber as closed, but are not in huc2m.trace. They probably would drain into Mexico if they could. 13030201 Playas Lake, NM 13020202 Nimbres River, NM Colorado River basin 14040200 Great Divide Closed Basin in Seaber 15030105 Bouse Wash, AZ NHD does not exit. Hillshade shows an exit towards Colorado River 15040003 Animas Valley; Seaber closed 15050201 Wilcox Playa, AZ; Seaber closed 15050305 Aguirre Valley, AZ; hillshade looks closed 9522000 all 4 regions These were already excluded but not on huc2m.trace list; they do not drain into the Colorado within the U.S 15080301 Whitewater Draw, AZ 15080302 San Bernardino Valley, AZ 15080303 Cloverdale, NM 15080101 San Simon Wash, AZ Columbia River basin These are not closed in Seaber, but Al Rea, USGS, knows that they are closed basins and they are in huc2m.trace 17040214 Beaver-Camas, ID drains into 215 17040215 Medicine Lodge, ID 17040216 Birch, ID 17040217 Little Lost, ID 17040218 Big Lost, ID 13353200 14128910 huc2m.trace HUM DEM NHD CA-cd 20030226 Some polygons added or removed based on problems found while deleting closed basins and recalculating drainage areas. Contributing drainage area recalculated. Column names and types modified to be consistent for all regions. New column added to region.gage_na and region.sect_na to give the drainage area for the watershed within the US only. Universe label for polygons deleted. 20030306 Individual shape files created of the complete watershed for each site from region.gage_na. These shape files are named with a leading 'b' followed by the station idenitifcation number. Leading zeros were dropped so that most shape files are 8.3 compliant. In addition a single shape file (nas_sect) was created (from region.sect_na) of the watersheds immediately upstream to the next site upstream, if present, or to the headwaters otherwise. All these shape files were created by exporting from ArcMap with the view set to decimal degrees NAD 83 and choosing the view projection. 20030310 Vector Complete chain 6491 Label point 1250 GT-polygon composed of chains 1250 Point 4 GT-polygon composed of rings 43 GT-polygon composed of rings 43 GT-polygon composed of rings 43 GT-polygon composed of rings 43 Albers Conical Equal Area 29.500000 45.500000 -96.000000 23.000000 0.000000 0.000000 coordinate pair 0.001892 0.001892 meters North American Datum of 1983 Geodetic Reference System 80 6378137.000000 298.257222 nasqan2k.pat Polygon attribute table U.S. Geological Survey FID Internal feature number. ESRI Sequential unique whole numbers that are automatically generated. Shape Feature geometry. ESRI Coordinates defining the features. AREA Area of feature in internal units squared. ESRI Positive real numbers that are automatically generated. PERIMETER Perimeter of feature in internal units. ESRI Positive real numbers that are automatically generated. NASQAN2K# Internal feature number. ESRI Sequential unique whole numbers that are automatically generated. NASQAN2K-ID User-defined feature number. ESRI 1- 2346 arbitrary value assigned by software during processing ESRI HUC250K Text item (to keep leading zeros) for 8-digit Hydrologic Unit Code for subregion. Areas outside the USA are set to 0. Hydrologic Unit Maps 0 17090012 250000 The Hydrologic Units were digitized from maps printed at this scale. HUC250 Numeric 8-digit Hydrologic Unit Code for subregion. These subregions were the building blocks for the construction of the digital NASQAN watersheds. Areas outside the USA are set to 0. Hydrologic Unit Maps 0 17090012 FIRST4 First 4 digits of the 8-digit huc. Hydrologic Unit Maps 0 1709 FIRST6 First 6 digits of the 8-digit huc. Hydrologic Unit Maps 0 170900 FIRST2 First 2 digits in the 8-digit huc, also called the Region. U.S. Geological Survey 5 17 HUC_NA Equals huc250 except for areas in Canada and Mexico . These areas are given a value of the 8-digit HUC in the USA into which water drains plus a 2-letter code, either "mx" or "ca", for example, 19010216ca. Some of these polygons outside the USA describe areas that drain into more than one US Hydrologic Unit in which case one of these U.S Hydrologic Unit Codes was assigned arbitrarily to these external areas along with the 2-letter country code. USGS 01010101 17090012 with possible concatenation of mx or ca nasqan2k.patgage_na Region feature that represents the entire contributing drainage area for the sampling site. The 'na' refers to North America as opposed to USA only. Because many sampling sites are on the same river system, many of these watersheds overlap and are difficult to present on a map. However this geographic aggregation of HUCs allows analysis by the entire watershed area including areas in Canada and Mexico. ESRI region feature created by ehopkins dataset creator. FID Internal feature number. ESRI Sequential unique whole numbers that are automatically generated. Shape Feature geometry. ESRI Coordinates defining the features. AREA Area of feature in internal units squared. ESRI Positive real numbers that are automatically generated. PERIMETER Perimeter of feature in internal units. ESRI Positive real numbers that are automatically generated. GAGE_NA# Internal feature number. ESRI Sequential unique whole numbers that are automatically generated. GAGE_NA-ID User-defined feature number = siteid ESRI 3216600 14246900 STAID Text variable for USGS gage identification number that allows the leading '0' to be retained. U.S. Geological Survey 03216600 14246900 SITEID Numeric code for USGS gage; see Supplemental Information U.S. Geological Survey 3216600 14246900 NAME USGS name for the gage. Generally a name includes both the water body and a nearby geographic reference point. USGS NWIS database See Supplemental Information section List of names for the 43 NASQAN stations active in year 2000. USGS NWIS database BASIN Abbreviation for one of 4 major river basins U.S. Geological Survey Miss Mississippi River basin U.S. Geological Survey RG Rio Grande basin U.S. Geological Survey Colo Colorado River basin U.S. Geological Survey Colum Columbia River basin U.S. Geological Survey MI2 Area of each region multiplied by the square-meters-to-square-miles conversion factor 0.0000003861. U.S. Geological Survey 272 1138446 MI2USA Area of each watershed in square miles that is within the United States. U.S. Geological Survey 272 1127787 nasqan2k.patgage_usa Region feature represents the contributing drainage area within the USA for each sampling site. Because many sampling sites are on the same river system, many of these watersheds overlap and are difficult to present on a map. This feature class allows analysis of the contributions from watershed within the USA . Often ancillary data such as pesticide application is available only for the United States. U.S. Geological Survey FID Internal feature number. ESRI Sequential unique whole numbers that are automatically generated. Shape Feature geometry. ESRI Coordinates defining the features. AREA Area of feature in internal units squared. ESRI Positive real numbers that are automatically generated. PERIMETER Perimeter of feature in internal units. ESRI Positive real numbers that are automatically generated. GAGE_USA# Internal feature number. ESRI Sequential unique whole numbers that are automatically generated. GAGE_USA-ID User-defined feature number = siteid USGS 3216600 14246900 STAID USGS gage identification number as text U.S. Geological Survey 03216600 14246900 SITEID USGS gage identification number U.S. Geological Survey 03216600 14246900 NAME USGS name for the gage. Generally a name includes both the waterbody and a nearby geographic reference point. USGS NWIS database See Supplemental Information section List of names for the 41 NASQAN stations active in year 2000. USGS NWIS database BASIN Abbreviation for one of 4 major river basins U.S. Geological Survey NWIS database Miss Mississippi River basin U.S. Geological Survey RG Rio Grande basin U.S. Geological Survey Colo Colorado River basin U.S. Geological Survey Colum Columbia River basin U.S. Geological Survey MI2 The area for the watershed above the gage excluding any areas outside the USA. Area of each region multiplied by the square-meters-to-square-miles conversion factor 0.0000003861. 272 1,134,306 nasqan2k.patsect_na This region feature class represents the contributing drainage area above the sampling site and below the upstream sampling site. For sites with no upstream sampling sites the features represent all the contributing upstream drainage area. This feature class allows analysis of the contributions from the watershed between sampling sites. For instance a pesticide application rate can be computed for the units of application to the receiving areas and inferences made about the causes of changes in sample concentrations between the sites on the river system. This feature class contains areas in Canada and Mexico. The 'na' refers to North America. U.S. Geological Survey FID Internal feature number. ESRI Sequential unique whole numbers that are automatically generated. Shape Feature geometry. ESRI Coordinates defining the features. AREA Area of feature in internal units squared. ESRI Positive real numbers that are automatically generated. PERIMETER Perimeter of feature in internal units. ESRI Positive real numbers that are automatically generated. SECT_NA# Internal feature number. ESRI Sequential unique whole numbers that are automatically generated. SECT_NA-ID User-defined feature number = siteid ESRI 3216600 14246900 STAID SITEID as a character item. USGS NWIS database 3216600 14246900 SITEID USGS gage identification number USGS NWIS database 03216600 14246900 NAME USGS gage name USGS NWIS database See Supplemental Information Gage name usually contains both the water feature name and a nearby location USGS NWIS database BASIN Abbreviation for one of 4 major river basins U.S. Geological Survey Miss Mississippi River watershed U.S. Geological Survey RG Rio Grande watershed U.S. Geological Survey Colo Colorado River watershed U.S. Geological Survey Colum Columbia River watershed U.S. Geological Survey MI2 Area in square miles of contributing drainage area above the sampling site and below any upstream sampling site including any area outside the USA. Area of each region multiplied by the square-meters-to-square-miles conversion factor 0.0000003861. Note: This value is computed from this data set and may differ from the drainage area published for the gage from the USGS NWIS database. 272 157,784 MI2USA Area of each region in square miles that is within the United States. See definition for MI2. U.S. Geological Survey 272 154484 nasqan2k.patsect_usa This region feature class represents the contributing drainage area above the sampling site and below the upstream sampling site (or headwaters). This feature class allows analysis of the contributions from the watershed between sampling sites. For instance a pesticide application rate can be computed for the units of application to the receiving areas and inferences made about the causes of changes in sample concentrations between the sites on the river system. This feature class includes only area within the USA. U.S. Geological Survey FID Internal feature number. ESRI Sequential unique whole numbers that are automatically generated. Shape Feature geometry. ESRI Coordinates defining the features. AREA Area of feature in internal units squared. ESRI Positive real numbers that are automatically generated. PERIMETER Perimeter of feature in internal units. ESRI Positive real numbers that are automatically generated. SECT_USA# Internal feature number. ESRI Sequential unique whole numbers that are automatically generated. SECT_USA-ID User-defined feature number = siteid ESRI 3216600 14246900 STAID SITEID as a character item. USGS NWIS database 03216600 14246900 SITEID USGS gage identification number USGS NWIS database 3216600 14246900 NAME USGS gage name USGS NWIS database See Supplemental Information Gage name usually contains both the water feature name and a nearby location USGS NWIS database BASIN Abbreviation for one of 4 major river basins U.S. Geological Survey Miss Mississippi River watershed U.S. Geological Survey RG Rio Grande watershed U.S. Geological Survey Colo Colorado River watershed U.S. Geological Survey Colum Columbia River watershed U.S. Geological Survey MI2 Area in square miles of contributing drainage area that is within the U.S.A. above the sampling site and below any upstream sampling site. Area of each region multiplied by the square-meters-to-square-miles conversion factor 0.0000003861. 272 157,784 Although polygons are included in the native data set, the NASQAN watersheds are represented by the region features that are aggregations of these polygons . Each of the 4 region feature classes represent different aggregations of the underlying polygons. Each feature class has attributes that describe the location and extent of the watersheds for the NASQAN gages. The polygon attributes refer to the Hydrologic Unit codes. The Region, Subregion, and Accounting Units are aggregations of the basic 8-digit cataloging units. No subdivisions of the 8-digit units are included in this dataset except for those that subdivide the huc containing a NASQAN gage. These subdivisions retain the value of the 8-digit huc. Polygons added from Canada and Mexico have attribute item huc250 set to 0. HUM U.S. Geological Survey Ask USGS - Water Webserver Team mailing

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Reston VA 20192 1-888-275-8747 (1-888-ASK-USGS) http://water.usgs.gov/user_feedback_form.html Although this data set has been used by the U.S. Geological Survey, U.S. Department of the Interior, no warranty expressed or implied is made by the U.S. Geological Survey as to the accuracy of the data and related materials. The act of distribution shall not constitute any such warranty, and no responsibility is assumed by the U.S. Geological Survey in the use of this data, software, or related materials. Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government. Export Full watersheds and point coverages 1 http://water.usgs.gov/GIS/dsdl/nasqan2k.tar Shape Shapes for individual watersheds zipped 1 http://water.usgs.gov/GIS/dsdl/nasq_shp.tar.gz None. This dataset is provided by USGS as a public service. 20041108 U.S. Geological Survey Ask USGS -- Water Webserver Team mailing

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Reston VA 20192 1-888-275-8747 (1-888-ASK-USGS) http://answers.usgs.gov/cgi-bin/gsanswers?pemail=h2oteam&subject=GIS+Dataset+nasqan2k FGDC Content Standards for Digital Geospatial Metadata FGDC-STD-001-1998