LOW-FLOW PROFILES OF THE UPPER OCMULGEE AND FLINT IN GEORGIA By R. F. Carter, E. H. Hopkins, and H. A. Perlman

U.S. GEOLOGICAL SURVEY Water-Resources Investigations Report 86-4176

Prepared in cooperation with the GEORGIA DEPARTMENT OF NATURAL RESOURCES ENVIRONMENTAL PROTECTION DIVISION

Doraville, Georgia 1986 DEPARTMENT OF THE INTERIOR DONALD PAUL MODEL, Secretary

U.S. GEOLOGICAL SURVEY Dallas L. Peck, Director

For additional information Copies of this report can be write to: purchased from:

District Chief, WRD U.S. Geological Survey U.S. Geological Survey Books and Open-File Reports Suite B Federal Center, Bldg. 41 6481 Peachtree Industrial Boulevard Box 25424 Doraville, Georgia 30360 Denver, Colorado 80225 CONTENTS Page

Abstract ------._....--..--_- - _.-..._ -_- i Introduction ------1 Area of study ------2 Stream miles ------2 Drainage areas ------2 Flow data ------__..._.. .--_ _-_- 4

Revision of published low-flow data ------4

Flow extension ------__-- 4

Diversions, return flows, and regulation ------5

Accuracy ------5

Use of the profiles ------...._-- _.._.. 5

Selected references ------_ ... ----- _ 7

Supplemental data tabular and graphical low-flow profiles ------8

Explanation of tables and graphs ------8

List of tables and profiles ------_._- 9

Alphabetical index ------232

ILLUSTRATIONS

Page

Figure 1. Subdivisions of Ocmulgee and Flint basins - - 3

111 CONVERSION FACTORS Factors for converting inch-pound units to International System (SI) units used in this report are listed below:

Multiply inch-pound units By To obtain SI units

Length mile (mi) 1.609 kilometer (km)

Area square mile (mi^) 2.590 square kilometer (km2 )

Flow cubic foot per second 28.32 liter per second (L/s) (ft3 /s) 0.02832 cubic meter per second (m3 /s) LOW-FLOW PROFILES OF THE UPPER OCMULGEE AND FLINT RIVERS IN GEORGIA

By R. F. Carter, E. H. Hopkins, and H. A. Perlman

ABSTRACT This report provides low-flow information for use in evaluating the capac­ ity of streams to supply withdrawals or to accept waste loads from potential new industries without exceeding the limits of State water-quality standards. The report is the first phase of a study of all stream basins north of the Fall Line in Georgia. It covers the Piedmont part of the Ocmulgee and Flint River basins. The low-flow characteristic presented is the minimum average flow for 7 consecutive days with a 10-year recurrence interval. The data are presented graphically as low-flow profiles (low flow as a function of distance along a stream channel) and as drainage-area profiles (drainage area as a function of distance along a stream channel). Low-flow profiles were constructed by in­ terpolation or extrapolation from points of known low-flow data. Low-flow profiles are included for all stream reaches where low-flow data of sufficient accuracy are available to justify computation of the profiles. Drainage-area profiles are included for all stream basins larger than 5 square miles. Flow records were not adjusted for diversions or other factors that cause measured flows to represent other than natural flow conditions. Profiles for 7-day minimum flows are omitted for stream reaches where natural flow is known to be significantly altered. INTRODUCTION The Ocmulgee and Flint Rivers and their tributaries in the area from the headwaters south of Atlanta, Ga., to the Fall Line are heavily used for water supply and waste disposal . Tributary streams have relatively low yields during drought periods and low-flow characteristics have been only partly defined in previous studies. This study was made to provide low-flow information for use in evaluating the capacity of these streams to supply withdrawals or to accept waste loads from potential new industries without exceeding the limits of State water- quality standards. The study was made by the U.S. Geological Survey as part of the cooperative water-resources program with the Georgia Department of Natural Resources, Environmental Protection Division. The purpose of this report is to compile available data used to determine the minimum average flow for 7 consecutive days with a 10-year recurrence interval (7Q10), and to present "7010 flow profiles" for all stream reaches where sufficient data of acceptable accuracy are available. Techniques used to estimate the profiles also are presented in this report. The 7-day low flow will be less than the 7Q10 low flow at intervals averaging 10 years in length; or the probability is 10 percent that the 7-day low flow in any one year will be less than the 7-day, 10-year low flow. AREA OF STUDY This report comprises the first phase of a larger study covering all stream basins north of the Fall Line in Georgia. It includes the Ocmulgee River basin above the Macon gage (02213000), stream mile 198.0, and the Flint River basin above a site about 5 miles east of Reynolds, stream mile 209.1 (fig. 1). The basins of Tobesofkee, Echeconnee, and Patsiliga Creeks are included in their entirety, although parts of each basin lie below the Fall Line in the upper Coastal Plain. For convenience in presentation, both major river basins were divided into subdivisions. Most subdivisions consist of a large tributary and its tribu­ taries. The main stem of the Ocmulgee River below Jackson Lake dam and two tributaries to Jackson Lake also are one subdivision. The main stem of the Flint River is subdivided into two segments, one upstream from Line Creek, the other segment from Line Creek to the southern limit of the study area. The principal numbering system for these subdivisions is shown on the loca­ tion map (fig. 1). The Ocmulgee River basin has 19 subdivisions numbered OP1 through OP19. The Flint River basin has 17 subdivisions numbered FP1 through FP17. Tributaries within these areas are identified by additional symbols. For example, a tributary to Yellow River in the subdivision numbered OP7 is numbered OP7F, and a tributary to that stream is numbered OP7F1. Identifying numbers for the subdivisions and the names of their respective drainages are given in the List of Tables and Profiles, in the section "Supplemental Data."

Stream Miles Stream miles were measured by an electronic digitizer on county maps published by the Georgia Department of Transportation. Mileages are presented as distances above the mouth of each stream. Mileages on the main stem of the Ocmulgee and Flint Rivers and on a few other streams are based on data provided by the U.S. Army Corps of Engineers (1985).

Drainage Areas Streamflows generally have a close relation to drainage area, especially on the same stream. Therefore a drainage-area profile (drainage area versus stream miles) is shown for all streams included in this report, even for streams where available data are insufficient for showing a flow profile. Drainage-area profiles are included for all streams in the study area having drainage areas of more than 5 mi?. So far as practicable, drainage-area data are based on previously published values. Supplemental drainage-area data were determined by approximate methods using an electronic digitizer and county maps published by the Georgia Department of Transportation. Time constraints did not allow use of 7 1/2-minute topographic quadrangles or rigid compliance with rules for accurate determination of drainage areas. Some additional drainage areas were determined by interpolation on short stream reaches where drainage-area increments were about proportional to increments of distance. Drainage areas determined by interpolation are identified by footnotes to the tables. Except for sites published in Carter (1959), drain­ age areas should be regarded as approximate. EXPLANATION

BOUNDARY OF SUBDIVISION

OP6 IDENTIFICATION NUMBER OF SUBDIVISION 02344500 A GAGING STATION AND NUMBER

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Base from U.S. Geological Survey Stat