USGS

August Median Streamflow on Ungaged Streams in Eastern Aroostook County, Maine

Water-Resources Investigations Report 03-4225

 

By Pamela J. Lombard, Gary D. Tasker, and Martha G. Nielsen

 

In cooperation with the AROOSTOOK WATER AND SOIL MANAGEMENT BOARD

 


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Abstract

Methods for estimating August median streamflow were developed for ungaged, unregulated streams in the eastern part of Aroostook County, Maine, with drainage areas from 0.38 to 43 square miles and mean basin elevations from 437 to 1,024 feet. Few long-term, continuous-record streamflow-gaging stations with small drainage areas were available from which to develop the equations; therefore, 24 partial-record gaging stations were established in this investigation. A mathematical technique for estimating a standard low-flow statistic, August median streamflow, at partial-record stations was applied by relating base-flow measurements at these stations to concurrent daily flows at nearby long-term, continuous-record streamflow- gaging stations (index stations). Generalized least-squares regression analysis (GLS) was used to relate estimates of August median streamflow at gaging stations to basin characteristics at these same stations to develop equations that can be applied to estimate August median streamflow on ungaged streams. GLS accounts for varying periods of record at the gaging stations and the cross correlation of concurrent streamflows among gaging stations. Twenty-three partial-record stations and one continuous-record station were used for the final regression equations.

The basin characteristics of drainage area and mean basin elevation are used in the calculated regression equation for ungaged streams to estimate August median flow. The equation has an average standard error of prediction from -38 to 62 percent. A one-variable equation uses only drainage area to estimate August median streamflow when less accuracy is acceptable. This equation has an average standard error of prediction from -40 to 67 percent. Model error is larger than sampling error for both equations, indicating that additional basin characteristics could be important to improved estimates of low-flow statistics.

Weighted estimates of August median streamflow, which can be used when making estimates at partial-record or continuous-record gaging stations, range from 0.03 to 11.7 cubic feet per second or from 0.1 to 0.4 cubic feet per second per square mile. Estimates of August median streamflow on ungaged streams in the eastern part of Aroostook County, within the range of acceptable explanatory variables, range from 0.03 to 30 cubic feet per second or 0.1 to 0.7 cubic feet per second per square mile. Estimates of August median streamflow per square mile of drainage area generally increase as mean elevation and drainage area increase.

TABLE OF CONTENTS

Abstract

Introduction

Purpose and Scope

Previous Studies

Location of Study Area

Acknowledgments

Data Collection and Analysis

Station Selection and Streamflow Measurements

Basin Characteristics

Estimating August Median Streamflow at Partial-Record Streamflow-Gaging Stations

Computing August Median Streamflow at Index Stations

Estimating August Median Streamflow at Partial-Record Stations

Estimating August Median Streamflow on Ungaged Streams

Statistical Methods

Ordinary Least-Squares Regression

Generalized Least-Squares Regression

Regional Regression of Expected August Median Discharge Using Generalized Least-Squares Regression

Estimating August Median Streamflow of Continuous-Record and Partial-Record Streamflow- Gaging Stations

Estimating August Median Streamflow on Ungaged Streams

Equations for Estimating August Median Streamflow on Ungaged Streams

Two-Variable Model

One-Variable Model

Weighted Estimates of August Median Streamflow at Partial- and Continuous-Record Streamflow-Gaging Stations

Summary and Conclusions

References Cited


For additional information write to:

 

District Chief

U.S. Geological Survey

Maine District

196 Whitten Road

Augusta, Maine 04330

http://me.water.usgs.gov

 

Copies of this report can be purchased from:

 

U.S. Geological Survey

Branch of Information Services

Box 25286, MS 517

Federal Center

Denver, CO 80225

 


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