Water Resources Applications Software

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Summary of GLSNET

       glsnet - Regional hydrologic regression and network analysis using
                generalized least squares

       The GLSNET procedure uses an analysis of residuals technique to
       estimate a regional regression equation to predict flow
       characteristics at ungaged sites.  The regression analysis assigns
       different weights to observed flow characteristics.  These weights
       are based on record length, cross correlation with flow
       characteristics at other sites, and an assumed model error

       Stedinger and Tasker (1985, 1986) documented the usefulness of an
       estimated generalized least squares (EGLS) regression procedure for
       regional regression of streamflow characteristics.  The EGLS
       procedure assigns different weights to observed flow characteristics
       based on their record length, cross correlation with flow
       characteristics at other sites, and the model error variance.
       Tasker and Stedinger (1989) provide further details on how the
       elements of the weighting matrix are determined.

       The problem of identifying the sites from which to collect future
       streamflow data is formulated as a mathematical program using
       regional information and is subject to budget constraints.  An
       approximate solution is obtained using a step-backward technique
       that identifies gaging station sites, either existing or new, to
       discontinue data collection, or not start data collection,
       respectively, if the budget is exceeded.  The method allows a
       network manager to design a nearly optimal streamflow data network
       for collecting regional information.

       Version 2.6 1998/05/21 - Network analysis changed to run a zero
          planning horizon.  Corrected a problem in the code that caused
          the program to quit if the user tried to have a 6th parameter in
          the network analysis regression equation.

       Version 2.5 1997/09/29 - Corrected an error in the calculation of
          the derivative of the objective function with respect to the
          number of years of record.

       Version 2.4 1997/05/09 - Changed how the average sampling error
          variance is computed in the network analysis.  Should be faster.
          Simplified procedures for recompiling program with different

       Version 2.3 1996/12/17 - Incorrect conversion of degree-minute-
          second latitudes and longitudes to decimal degrees (off by a
          factor of 10) has been corrected.  This would have been a problem
          only in the following cases:

          1.  Latitudes and longitudes were stored in the WDM attributes
          LATDMS & LNGDMS.  (Note that data entered in the iowdm options
          peak, n-day, and (or) basin would not have this problem as
          lat/lng were stored as decimal degrees in attributes LATDEG &

          2.  When proposed stations were being added for the network

       Version 2.2 1995/10/08 - Increased the maximum number of stations
          from 300 to 600.

          1995/10/21 - Fixed graphics to correctly handle Modify/Device.

          1995/11/14 - Correction made in how peak qualification codes are
          being handled.

          There was a problem if the user specified no qualification codes
          (all peaks were to be included).  In this case, peaks that had no
          qualification codes may not have been included.

       Version 2.1 1994/11/01 - Corrections made in the partial record
          option and the ordinary least squares option.

          Corrected a bug that caused the program to bomb when the user
          entered an invalid name for the input file.

          Corrected bugs that caused the ordinary least squares option to

       At each site in the network of gages a set of basin characteristics,
       such as drainage area, basin slope, and mean annual precipitation; a
       set of flow characteristics, such as 100-year flood, mean annual
       flood, or 7-day 10-year low flow; and a time series of observed
       flows, such as annual peaks, or annual 7-day low flows; are required
       to be in a WDM file.

       Output is the final regression model and related residual analysis
       including influence statistics and various optional graphs.  In
       addition, for the network analysis a list of stations to continue
       given various budget levels is output.

       GLSNET is written in Fortran 77 with the following extension: use of
       include files.  The ANN, WAIDE, AWSTAT, GRAPH, STATS, AIDE, WDM,
       ADWDM, and UTIL libraries from LIB are required to recompile. For
       more information, see System Requirements in LIB.

       Tasker, G.D., and Stedinger, J.R., 1989, An operational GLS model
          for hydrologic regression: Journal of Hydrology, v. 111, p.

       Asquith, W.H., and Slade R.M, Jr., 1997, Regional Equations for
          estimation of peak-streamflow frequency for natural basins in
          Texas, U.S.Geological Survey Water-Resources Investigation Report

       Asquith, W.H., 1998, Peak-flow frequecny for tributaries of the
          Colorado   River downstream of Austin, Texas, U.S.Geological
          Survey Water-Resources Investigation Report 98-4015.

       Brabets, T.P., 1996, Evaluation of the Streamflow-gaging network of
          Alaska in providing regional streamflow information,
          U.S.Geological Survey Water-Resources Investigation Report

       Clement, R.W., 1987, Floods in Kansas and techniques for estimating
          their magnitude and frequency:  U.S. Geological Survey Water-
          Resources Investigations Report 87-4008.

       Curtis, G.W., 1987, Techniques for estimating flood-peak discharges
          and frequencies on rural streams in Illinois:  U.S. Geological
          Survey Water-Resources Investigations Report 87-4207.

       Hodge, S.A, and Tasker, G.D., 1995, Magnitude and frequency of
          floods in   Arkansas, U.S.Geological Survey Water-Resources
          Investigation Report   95-4224.

       Landers, M.N., and Wilson, K.V., Jr., 1991, Flood characteristics of
          Mississippi streams:  U.S. Geological Survey Water-Resources
          Investigations Report 91-4037.

       Livingston, R.K., and Minges, D.R., 1987, Techniques for estimating
          regional flood characteristics of small rural watersheds in the
          Plains Region of eastern Colorado:  U.S. Geological Survey Water-
          Resources Investigations Report 87-4094, 72 p.

       Ludwig, A.H., and Tasker, G.D., 1993, Regionalization of low flow
          characteristics of Arkansas streams:  U.S. Geological Survey
          Water-Resources Investigations Report 93-4013, 19 p.

       Lui, S., and Stedinger, J.R., 1991, Low flow frequency analysis with
          ordinary and tobit regression: Proc. 18th annual conference and
          symposium ASCE WRPMD, p. 27-31.

       Lumia, R., 1991, Regionalization of flood discharges for rural,
          unregulated streams in New York:  U.S. Geological Survey Water-
          Resources Investigations Report 90-4197.

       Medina, K.D., and Tasker, G.D., 1985, Analysis of surface water data
          network in Kansas for effectiveness in providing regional
          information: U.S. Geological Survey Water-Supply Paper 2203, 27

       Roberts, J.W., and Kolton, G.F., 1989, Techniques for estimating
          flood-peak discharges of rural, unregulated streams in Ohio:
          U.S. Geological Survey Water-Resources Investigations Report

       Stedinger, J.R., and Tasker, G.D., 1985, Regional hydrologic
          analysis 1: Water Resources Research, v. 21, no. 9, p. 1421-1432.

       Stedinger, J.R., and Tasker, G.D., 1986, Regional hydrologic
          analysis 2: Water Resources Research, v. 22, no. 10, p.

       Tasker, G.D., 1986, Generating efficient gaging plans for regional
          information in Moss, M.E., ed., Integrated Design of Hydrological
          Networks: International Association of Hydrological Sciences
          publication no. 158, p. 269-281.

       Tasker, G.D., 1991, Identifying stream gauges to operate for
          regional information: Transportation Research Record 1319, p.

       Vogel, R.M., and Kroll, C.N., 1990, Generalized low-flow frequency
          relationships for ungaged sites in Massachusetts: Water Resources
          Bulletin, v. 26, no. 2, p. 241-253.

       Statistical Approach to Surface-Water Hydrologic Analysis
       (SW2011TC), offered annually at the USGS National Training Center.

       Operation and Distribution:
          U.S. Geological Survey
          Hydrologic Analysis Software Support Program
          437 National Center
          Reston, VA 20192

       Official versions of U.S. Geological Survey water-resources analysis
       software are available for electronic retrieval via the World Wide
       Web (WWW) at:


       and via anonymous File Transfer Protocol (FTP) from:

         (path: /pub/software).

       The WWW page and anonymous FTP directory from which the GLSNET
       software can be retrieved are, respectively:


       annie(1) - Program to list, table, plot data in a WDM file
       iowdm(1) - Program to store time-series data in a WDM file
       peakfq(1) - Flood-frequency analysis based on Bulletin 17B
       swstat(1) - Surface-water statistics
       wdm(1) - Watershed Data Management system

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