The attributes associated with each streamgage include:
Station number Station name Station latitude (decimal degrees in North American Datum of 1983, NAD 83) Station longitude (decimal degrees in NAD 83) First date (year, month, day) of streamflow data Last date (year, month, day) of streamflow data Number of days of streamflow data Minimum and maximum daily flow for the period of record (cubic feet per second) Percentiles (1, 5, 10, 20, 25, 50, 75, 80, 90, 95, 99) of daily flow for the period of record (cubic feet per second) Average and standard deviation of daily flow for the period of record (cubic feet per second) Mean annual base-flow index (BFI: see supplemental information) computed for the period of record (fraction, ranging from 0 to 1) Year-to-year standard deviation of the annual base-flow index computed for the period of record (fraction) Number of years of data used to compute the base-flow index (years) Reported drainage area (square miles) Reported contributing drainage area (square miles) National Water Information System (NWIS)-Web page URL for streamgage Hydrologic Unit Code (HUC, 8 digit) Hydrologic landscape region (HLR) River Reach File 1 (RF1) segment identification number (E2RF1##)
Station numbers, names, locations, and drainage areas were acquired through the National Water Information System (NWIS)-Web (<http://water.usgs.gov/nwis>) on November 20, 2001. The streamflow data used to compute flow characteristics were copied from the Water server (water.usgs.gov:/www/htdocs/nwisweb/data1/discharge/) on November 2, 2001.
The missing value indicator for all attributes is -99. Some streamflow characteristics are missing for: (1) streamgages measuring flow subject to tidal effects, which cause flow to reverse directions, (2) streamgages with site information but no streamflow data at the time the data were retrieved, and (3) streamgages with record length too short to compute the base-flow index.
A base-flow index (BFI) was computed for the streamgages using a Fortran program written by Tony Wahl (Bureau of Reclamation. U.S. Department of the Interior) and Ken Wahl (U.S. Geological Survey) (<http://www.usbr.gov/pmts/hydraulics_lab/twahl/bfi/index.html>). The computer program name is bfi41.f and was the most current version available at the time. The computer program was compiled on a Sun Unix system and run with the default parameter values.
The BFI Web page (<http://www.usbr.gov/pmts/hydraulics_lab/twahl/bfi/index.html>) states:
"The BFI program was developed to make the base-flow separation process less tedious and more objective. The program implements a deterministic procedure proposed in 1980 by the British Institute of Hydrology. The method combines a local minimums approach with a recession slope test. The program estimates the annual base-flow volume of unregulated rivers and streams and computes an annual base-flow index (BFI, the ratio of base flow to total flow volume for a given year) for multiple years of data at one or more gage sites. Although the method may not yield the true base flow as might be determined by a more sophisticated analysis, the index has been found to be consistent and indicative of base flow, and thus may be useful for analysis of long term base-flow trends. Users should be very cautious about using methods such as this for short-term storm events or for locations where streamflow is affected by upstream regulation, such as reservoir releases. In general, the method interprets most regulated releases as base flow. If the program is used for regulated streams, the effects of regulation must be carefully accounted for through manual adjustment of the program output."
BFI references:
Wahl, K.L., and Wahl, T.L., 1995, Determining the flow of Comal Springs at New Braunfels, Texas, In Proceedings of Texas Water '95, American Society of Civil Engineers, August 16-17, 1995 San Antonio, Texas: American Society of Civil Engineers, p. 77-86, information available on the World Wide Web, accessed March 25, 2003 , at URL <http://www.usbr.gov/pmts/hydraulics_lab/twahl/bfi/texaswater95/comalsprings.html>
Wahl, K.L., and Wahl, T.L., 1988, Effects of regional ground-water declines on streamflows in the Oklahoma Panhandle, In Proceedings of Symposium on Water-Use Data for Water Resources Management: Tucson, Arizona, American Water Resources Association, p. 239-249, information available on the World Wide Web, accessed March 25, 2003, at URL <http://www.usbr.gov/pmts/hydraulics_lab/twahl/bfi/bfi_beaver_river.pdf>
The use of firm, trade, and brand names is for identification purposes only and does not constitute endorsement by the U.S. government.
1. The station identification number, station name, degrees-minutes-seconds (DMS) latitude, DMS longitude, latitude-longitude datum, State code, drainage area, and contributing drainage for each streamgage with daily discharge values in all States in the conterminous United States were obtained from NWIS-Web (<http://water.usgs.gov/nwis>).
2. The ARCINFO computer program infopoint.aml (Curtis Price, USGS, written commun., 2001) was used to generate a point coverage of the streamgage locations. In generating the point coverage, all the North American Datum of 1927 (NAD 27) points were projected into NAD 83.
3. Daily streamflow data for all streamgages were copied from the files located in the subdirectories of water.usgs.gov/www/htdocs/nwisweb/data1/discharge/.
4. The Perl program getstat.pl (Xiaodong Jian, USGS, written commun., 2001) was used to compute the time period and flow statistics for each streamgage.
5. A base-flow index (BFI) program (<http://www.usbr.gov/pmts/hydraulics_lab/twahl/bfi/>) was used to estimate the fraction of "base flow" in total streamflow. Base flow is the slowly varying component of streamflow and is assumed to be from ground-water discharge to streams. (See Supplemental_Information.)
6. The dataset was projected into decimal degrees (NAD 83) and saved as a shapefile for compatibility with the National Atlas of the United States. In addition, the attribute table was saved as a tab-delimited text file for use in MapInfo, ArcView3, Atlas GIS, and Microsoft Excel.
The use of firm, trade, and brand names is for identification purposes only and does not constitute endorsement by the U.S. Geological Survey.
Station number Station name Station latitude Station longitude NWIS-Web page URL for streamgage Reported drainage area (square miles) Reported contributing drainage area (square miles) Hydrologic Unit Code (HUC, 8 digit) Hydrologic landscape region (HLR) River Reach File 1 (RF1) segment identification number (E2RF1##)
The flow-characteristics information for each streamgage include:
Minimum and maximum daily flow for the period of record (cubic feet per second) Percentiles (1, 5, 10, 20, 25, 50, 75, 80, 90, 95, 99) of daily flow for the period of record (cubic feet per second) Average and standard deviation of daily flow for the period of record (cubic feet per second) Mean annual base-flow index (BFI) computed for the period of record (fraction, ranging from 0 to 1) Year-to-year standard deviation of the annual base-flow index computed for the period of record (fraction) Number of years of data used to compute the base-flow index (years) First date (year, month, day) of streamflow data Last date (year, month, day) of streamflow data Number of days of streamflow data
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.