Estimating Mean Annual Streamflow of Rural Streams in Kentucky

Abstract

Mean annual streamflow ( Q a ), defined as the mean of the series of annual mean streamflow values, was determined for selected rural stream sites in Kentucky. Streamflow data for the available period of record through the 1999 water year (October 1, 1998-September 30, 1999) at 235 continuous-record streamflow-gaging stations with at least 5 years of record located in and adjacent to Kentucky were used in the analysis. Record-extension procedures were applied for selected gaging stations to reduce time-sampling error and, thus, improve estimates of the long-term Q a .

Techniques to estimate the Q a at ungaged stream sites in Kentucky were developed. One-, two-, and three-variable regression equations that included total drainage area, station latitude minus 36 degrees, and mean basin elevation as explanatory variables were developed by use of ordinary- and generalized-least-squares regression. The three-variable regression equation has an approximate average standard error of prediction of 13.7 percent. The one- and two-variable equations exhibit geographical biases, and the indicated standard errors of prediction may poorly estimate the true prediction errors, depending upon the location in the State. Therefore, the three-variable equation should be used for estimating mean annual streamflow of rural streams in Kentucky whenever possible.

Table of Contents

   Abstract
   Introduction
      Purpose and scope
      Previous studies
      Acknowledgments
   Description of study area
      Climate
      Physiography and geology
   Compilation and review of streamflow data
   Mean annual streamflow estimates for gaged stream sites
   Development of the technique for estimating mean annual streamflow for ungaged, rural stream sites
      Basin characteristics
      Regression analysis
      Limitations and accuracy
   Procedures for estimating mean annual streamflow at stream sites in Kentucky
      Stream sites with gage information
         Sites at gage locations
         Sites near gage locations
         Sites between gage locations
      Stream sites with no gage information
   Example applications of estimating equations
   Summary
   References cited
   Glossary

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Section 1: (6.23MB)
   Abstract
   Introduction
      Purpose and scope
      Previous studies
      Acknowledgments
   Description of study area
      Climate
      Physiography and geology
   Compilation and review of streamflow data
   Mean annual streamflow estimates for gaged stream sites
   Development of the technique for estimating mean annual streamflow for ungaged, rural stream sites
      Basin characteristics
      Regression analysis
      Limitations and accuracy
   Procedures for estimating mean annual streamflow at stream sites in Kentucky
      Stream sites with gage information
         Sites at gage locations
         Sites near gage locations
         Sites between gage locations
      Stream sites with no gage information

Section 2: (1.85MB)
   Example applications of estimating equations
   Summary
   References cited
   Glossary