Methods for Estimating Selected Low-Flow Frequency Statistics and Mean Annual Flow for Ungaged Locations on Streams in Alabama

Scientific Investigations Report 2020-5099
Prepared in cooperation with Alabama Power; Alabama Farmers Federation; Alabama Association of Conservation Districts; Alabama Association of Resource Conservation and Development Councils; Alabama Department of Agriculture and Industries; Alabama Department of Conservation and Natural Resources— Wildlife and Freshwater Fisheries Division; Alabama Department of Economic and Community Affairs—Office of Water Resources; Alabama Department of Environmental Management; Alabama Soil and Water Conservation Committee; Choctawhatchee, Pea and Yellow Rivers Watershed Management Authority; Geological Survey of Alabama; and The University of Alabama—Alabama Water Institute
By: , and 

Links

  • Document: Report (3.54 MB pdf)
  • Appendixes:
    • Appendix 1 (12.7 kB csv) — U.S. Geological Survey streamgages that were excluded from the regional regression analysis for estimating selected low-flow frequency statistics and mean annual flow for ungaged locations in Alabama
    • Appendix 1 (18.1 kB xlsx) — U.S. Geological Survey streamgages that were excluded from the regional regression analysis for estimating selected low-flow frequency statistics and mean annual flow for ungaged locations in Alabama
    • Appendix 2 (27.6 kB csv) — U.S. Geological Survey streamgages and independent and dependent variables used in the low-flow frequency and mean annual flow regression analyses for ungaged locations on streams in Alabama
    • Appendix 2 (49.6 kB xlsx) — U.S. Geological Survey streamgages and independent and dependent variables used in the low-flow frequency and mean annual flow regression analyses for ungaged locations on streams in Alabama
  • Data Release: USGS data release — Supporting data for estimating selected low-flow frequency statistics and mean annual flow for ungaged locations on streams in Alabama
  • Version History: Version History (1.47 kB txt)
  • Download citation as: RIS | Dublin Core

Abstract

Streamflow data and statistics are vitally important for proper protection and management of the water quality and water quantity of Alabama streams. Such data and statistics are generally available at U.S. Geological Survey streamflow-gaging stations, also referred to as streamgages or stations, but are often needed at ungaged stream locations. To address this need, the U.S. Geological Survey, in cooperation with numerous Alabama State agencies and organizations, developed regional regression equations for estimating selected low-flow frequency statistics and mean annual flow for ungaged locations on streams in Alabama that are not substantially affected by tides, regulation, diversions, or other anthropogenic influences. A small percentage of the streamgages included in this study experience zero flows during certain periods; thus, the final low-flow frequency regression equations were developed by using weighted left-censored regression analyses to analyze the flow data in an unbiased manner, with weights based on number of years of record.

The equations developed include the annual minimum 1- and 7-day average streamflows with a 10-year recurrence interval (referred to as the 1Q10 and 7Q10 flows), the annual minimum 7-day average streamflow with a 2-year recurrence interval (referred to as the 7Q2 flow), and the mean annual flow using data from 174 streamgages from Alabama and surrounding States. For the 1Q10, 7Q2, and 7Q10 low-flow frequency statistics, the regional regression equations are functions of drainage area, streamflow-variability index, mean annual precipitation, and percentage of the drainage basin located in the Piedmont and Southeastern Plains ecoregions. The mean annual flow regression equation is a function of drainage area, mean annual precipitation, and percentage of the drainage basin located in the Southeastern Plains ecoregion. For the mean annual flow regression equation, the average standard error of estimate was 11.2 percent. For the selected low-flow frequency equations, the average standard errors of estimate ranged from 18.1 to 38.8 percent.

The regional regression equations developed from this investigation have been incorporated into the U.S. Geological Survey StreamStats application for Alabama. StreamStats (https://streamstats.usgs.gov/ss/) is a web-based geographic information system application that delineates drainage basins at selected stream locations and then generates the needed basin characteristics for available regional regression equations. Along with the low-flow frequency equations developed in this investigation, the StreamStats application also has regional regression equations for estimating flood-frequency statistics at locations on rural and urban streams in Alabama.

Suggested Citation

Feaster, T.D., Kolb, K.R., Painter, J.A., and Clark, J.M., 2020, Methods for estimating selected low-flow frequency statistics and mean annual flow for ungaged locations on streams in Alabama (ver. 1.1, November 20, 2020): U.S. Geological Survey Scientific Investigations Report 2020–5099, 21 p., https://doi.org/10.3133/sir20205099.

ISSN: 2328-0328 (online)

ISSN: 2328-031X (print)

Study Area

Table of Contents

  • Acknowledgments
  • Abstract
  • Introduction
  • Selection of Streamgages
  • Physical and Climatic Basin Characteristics
  • Methods for Estimating Low-Flow Frequency Statistics and Mean Annual Flow at Ungaged Locations in Alabama
  • StreamStats
  • Summary
  • References Cited
  • Appendix 1. U.S. Geological Survey streamgages that were excluded from the regional regression analysis for estimating selected low-flow frequency statistics and mean annual flow for ungaged locations in Alabama
  • Appendix 2. U.S. Geological Survey streamgages and independent and dependent variables used in the low-flow frequency and mean annual flow regression analyses for ungaged locations on streams in Alabama

Additional publication details

Publication type Report
Publication Subtype USGS Numbered Series
Title Methods for estimating selected low-flow frequency statistics and mean annual flow for ungaged locations on streams in Alabama
Series title Scientific Investigations Report
Series number 2020-5099
DOI 10.3133/sir20205099
Edition Version 1.0: September 21, 2020; Version 1.1: September 29, 2020; Version 1.2: November 20, 2020
Year Published 2020
Language English
Publisher U.S. Geological Survey
Publisher location Reston, VA
Contributing office(s) Lower Mississippi-Gulf Water Science Center
Description Report: vii, 21 p.; Appendixes: 4; Data Release; Version History
Country United States
State Alabama
Online Only (Y/N) N
Additional Online Files (Y/N) Y
Google Analytic Metrics Metrics page
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