U.S. Department of the Interior

U.S. Geological Survey

Open-File Report 2010–1263

Surface-Water Quality-Assurance Plan 

for the U.S. Geological Survey 

Georgia Water Science Center, 2010
Cover photographs.

Front and back: USGS hydrographer making a measurement of streamflow on the Armuchee 

Creek near Armuchee, Georgia (USGS streamgage 02388010). Photograph by Thear K. Fraley.

Back lower left: USGS hydrographer making a measurement of streamflow on the New River at 

Georgia State Highway 100, near Corinth, Georgia (USGS streamgage 02338660). Photograph by 

Thear K. Fraley.

Back lower right: USGS hydrographer making a measurement of streamflow on the Upatoi Creek 

near Columbus, Georgia (USGS streamgage 02341800). Photograph by Jonathan B. Evans.
Surface-Water Quality-Assurance Plan 

for the U.S. Geological Survey 

Georgia Water Science Center, 2010

By Anthony J. Gotvald

Open-File Report 2010–1263

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

KEN SALAZAR, Secretary

U.S. Geological Survey

Marcia K. McNutt, Director

U.S. Geological Survey, Reston, Virginia: 2010

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Although this report is in the public domain, permission must be secured from the individual copyright owners to 

reproduce any copyrighted materials contained within this report.

Suggested citation:

Gotvald, A.J., 2010, Surface-water quality-assurance plan for the USGS Georgia Water Science Center, 2010: 

U.S. Geological Survey Open-File Report 2010–1263, 43 p.
iii

Contents

Abstract...........................................................................................................................................................1

Introduction.....................................................................................................................................................1

Responsibilities ..............................................................................................................................................1

Collection of Stage and Streamflow Data .................................................................................................3

Gaging Station Installation and Maintenance .................................................................................3

Measurement of Stage ........................................................................................................................4

Gage Documents...................................................................................................................................5

Levels ....................................................................................................................................................6

Site Documentation..............................................................................................................................6

Station Descriptions....................................................................................................................7

Photographs..................................................................................................................................7

Direct Measurements ..........................................................................................................................7

Field Notes ....................................................................................................................................9

Acceptable Equipment................................................................................................................9

Alternative Equipment...............................................................................................................10

Indirect Measurements .....................................................................................................................10

Peak-Flow Files ...................................................................................................................................11

Crest-Stage Gages..............................................................................................................................11

Artificial Controls ................................................................................................................................11

Flood Conditions..................................................................................................................................12

Low-Flow Conditions..........................................................................................................................12

Cold-Weather Conditions ..................................................................................................................13

Storm-Surge Sensor Network ..........................................................................................................13

Processing and Analyzing Stage and Streamflow Data .......................................................................14

Real-Time Streamflow Data ..............................................................................................................14

Web-Site Presentation .............................................................................................................14

Handling Errors...........................................................................................................................14

Data-Qualification Statements ................................................................................................15

Measurement and Field Notes .........................................................................................................15

Continuous Record .............................................................................................................................15

Records and Computation.................................................................................................................16

Records-Management System................................................................................................16

Procedures for Processing and Checking Records.............................................................16

Gage Height .......................................................................................................................16

Levels ................................................................................................................................16

Rating ................................................................................................................................17

Rating Numbering System...............................................................................................17

Datum and Gage-Height Corrections and Shifts .........................................................17

Hydrographs ......................................................................................................................18

Station Analysis ................................................................................................................18
iv

Winter Records .................................................................................................................19

Furnished Record..............................................................................................................19

Daily-Values Table ............................................................................................................19

Manuscript and Annual Report ......................................................................................19

Instantaneous Data Archive ...........................................................................................20

Review of Records.....................................................................................................................20

Crest-Stage Gages..............................................................................................................................20

Office Setting................................................................................................................................................21

Work Plan.............................................................................................................................................21

File Folders for Surface-Water Stations .........................................................................................21

Field-Trip Folders.................................................................................................................................21

Level Notes ..........................................................................................................................................21

Station Descriptions...........................................................................................................................21

Discontinued Stations........................................................................................................................21

Map Files..............................................................................................................................................22

Archiving ..............................................................................................................................................22

Revision of Records............................................................................................................................22

Communication of New Methods and Current Procedures ........................................................22

Collection of Precipitation Data ................................................................................................................23

Rain-Gage Installation and Maintenance.......................................................................................23

Rain-Gaging Station Descriptions....................................................................................................23

Processing and Analyzing Precipitation Data .......................................................................................23

Processing of Real-Time Precipitation Data ..................................................................................23

Web-Site Presentation .............................................................................................................24

Review of Real-Time Precipitation Data ................................................................................24

Handling Errors...........................................................................................................................24

Continuous Record .............................................................................................................................24

Records and Computation.................................................................................................................24

Procedures for Processing and Checking Records.............................................................25

Data Corrections...............................................................................................................25

Estimating Missing Record .............................................................................................25

Station Analysis ................................................................................................................25

Daily Sum Values Table....................................................................................................25

Manuscript and Annual Report ......................................................................................25

Review of Records.....................................................................................................................25

Collection of Sediment Data ......................................................................................................................26

Sampling Procedures.........................................................................................................................26

Field Notes ..................................................................................................................................26

Equipment Use, Care, and Maintenance ...............................................................................27

Sample Handling and Storage.................................................................................................27

High-Flow Conditions .........................................................................................................................27

Cold-Weather Conditions ..................................................................................................................27

Site Documentation............................................................................................................................27
v

Processing and Analysis of Sediment Data ............................................................................................28

Sediment Laboratory..........................................................................................................................28

Sediment-Station Analysis................................................................................................................28

Sediment-Analysis Results ...............................................................................................................28

Sediment-Data Storage .....................................................................................................................28

Database Management ..............................................................................................................................28

Publication of Surface-Water Data ..........................................................................................................29

Publication Policy ...............................................................................................................................29

Types of Publications .........................................................................................................................29

Review Process...................................................................................................................................29

Safety ...........................................................................................................................................................30

Training ..........................................................................................................................................................30

References Cited..........................................................................................................................................31

Appendix 1. U.S. Geological Survey Technical Memorandums Cited................................................33

Office of Surface Water (OSW) .......................................................................................................33

Water Resources Discipline (WRD).................................................................................................33

Office of Water Quality (OWQ) .........................................................................................................33

Appendix 2. Hydrologic Monitoring and Analysis Section—Surface-Water 

Electronic Archiving.......................................................................................................................34

Archive Directory Structure for Station Description, Station Manuscripts, 

Station Analysis, and Station Photo Files..........................................................................34

Archive Directory Structure for Electronic Data Logger (EDL) Data Files ................................35

Archive Directory Structure for ADCP Files...................................................................................35

Archive Directory Structure for ADV Files .....................................................................................36

Archive Directory Structure for Index Velocity Files ....................................................................36

Responsibilities ...................................................................................................................................37

Appendix 3. Hydroacoustic Instrumentation—Standards, Policies, and Procedures....................38

Acoustic Doppler Current Profiler ...................................................................................................38

ADCP Quality-Assurance Folder.............................................................................................38

Field Procedures........................................................................................................................38

Office Post-Field Procedures...................................................................................................39

Acoustic Doppler Velocimeter..........................................................................................................39

Field Measurements..................................................................................................................39

Measurement Documentation.................................................................................................41

Measurement Quality Assurance ...........................................................................................41

Periodic Quality-Assurance Checks.......................................................................................41

Index-Velocity Meter..........................................................................................................................42

Installation...................................................................................................................................42

Field Procedures........................................................................................................................42

Data Quality Assurance............................................................................................................43

Discharge Computation ............................................................................................................43
vi

Acronyms Used in This Report

ADAPS Automated Data Processing System 

ADCP acoustic Doppler current profiler 

ADR annual data report 

ADV acoustic Doppler velocimeter

ADVM acoustic Doppler velocity meter 

CAP culvert-analysis program 

CSG crest-stage gage 

Data Chief Chief of the Hydrologic Monitoring and Analysis Section 

DCP data-collection platform 

DD data descriptor 

DECODES Device Conversion and Delivery System 

DS-CI Discontinued Station Maintenance-Capital Improvement 

DOI Learn Department of Interior’s Learning Management System 

EDI equal-discharge increment 

EWI equal-width increment 

FISP Federal Interagency Sedimentation Program 

FRC Federal Record Center 

GaWSC Georgia Water Science Center 

GZF gage-height of zero flow 

IDA Instantaneous Data Archive 

MEWI multiple equal-width increment 

NWIS National Water Information System

NWISWEB National Water Information System Web 

OSW Office of Surface Water 

OWQ Office of Water Quality 

PC personal computer 

QA quality assurance 

QA Plan Surface-Water Quality-Assurance Plan 

QWDATA NWIS Water-Quality subsystem

REX regional executive 

RMS Records Management System 

RP reference point 

SAC slope-area computation 

SEWI single equal-width increment 

SIMS Site Information Management System 

SSC suspended-sediment concentration 

SWAMI Surface-Water Measurement and Inspection 

SWS Surface-Water Specialist 

SWUC Surface-Water Unit Chief 

TSS total suspended solids 

TWRI Techniques of Water-Resources Investigations 

USGS U.S. Geological Survey

UWI unequal-width increment 

WDR Water Data Report 

WRD Water Resources Discipline

WSPRO Water-Surface Profile Computation
Surface-Water Quality-Assurance Plan 

for the U.S. Geological Survey 

Georgia Water Science Center, 2010

By Anthony J. Gotvald

Abstract

The U.S. Geological Survey requires that each Water 

Science Center prepare a surface-water quality-assurance plan 

to describe policies and procedures that ensure high quality 

surface-water data collection, processing, analysis, computer 

storage, and publication. The Georgia Water Science Center’s 

standards, policies, and procedures for activities related to 

the collection, processing, analysis, computer storage, and 

publication of surface-water data are documented in this 

Surface-Water Quality-Assurance Plan for 2010.

Introduction

The U.S. Geological Survey (USGS) was established by 

an Act of Congress on March 3, 1879, to provide a permanent 

Federal agency to perform the systematic and scientific 

“classification of the public lands, and examination of the 

geologic structure, mineral resources, and products of the 

national domain.” Surface-water activities in the Georgia 

Water Science Center (GaWSC) are part of the overall 

mission of the USGS to appraise the Nation’s water resources. 

Surface-water information—including streamflow, stage, 

precipitation, and sediment data—is used by Federal, State, 

and local agencies for resources planning and management. 

The GaWSC conducts surface-water data-collection activities 

throughout Georgia from offices in Atlanta, Albany, Savannah, 

and Tifton. A field office Chief Technician, under the supervision of the Chief of the Hydrologic Monitoring and Analysis 

Section (Data Chief), supervises operations in each office.

This Surface-Water Quality-Assurance Plan (QA Plan) 

documents the standards, policies, responsibilities, and 

procedures used by the GaWSC for activities related to the 

collection, processing, analysis, computer storage, and publication of surface-water data. The QA Plan identifies individual 

responsibilities for ensuring that stated National policies and 

procedures are followed. The plan also serves as a guide for 

all GaWSC personnel involved in surface-water activities and 

as a resource for identifying memorandums, publications, 

and other literature that describe associated techniques and 

requirements in more detail. 

The scope of this report includes discussions of policies 

and procedures that are followed by the GaWSC for all 

surface-water data-collection activities. Specific types of 

surface-water data include stage, streamflow, precipitation, 

sediment, and basin characteristics. In addition, issues related 

to management of the computer database and employee 

safety and training are addressed. Although the procedures 

and products of interpretive projects are subject to the criteria 

presented in this report, specific interpretive projects are 

required to have separate and complete QA Plans.

This QA Plan is reviewed and revised at least once every 

3 years to ensure that responsibilities and methodologies 

are current and that ongoing procedural and instrumentation 

improvements are documented effectively.

Responsibilities

Quality assurance (QA) is an ongoing process. Achieving 

and maintaining high-quality standards for surface-water data 

are accomplished by specific actions carried out by specific 

persons. Errors and deficiencies can result when individuals 

do not carry out their responsibilities. Clear and specific 

statements of responsibilities promote an understanding of 

each person’s duties in the overall process of assuring surfacewater data quality. The responsibility for implementation of 

the QA Plan is distributed throughout the GaWSC. Much of 

the responsibility rests with field offices and the Hydrologic 

Monitoring and Analysis Section; however, the GaWSC 

Director ultimately is responsible for quality assurance. The 

following list summarizes responsibilities of GaWSC personnel involved in the collection, processing, analysis, computer 

storage, and publication of surface-water data. 
2 Surface-Water Quality-Assurance Plan for the U.S. Geological Survey Georgia Water Science Center, 2010

Responsibilities of the Georgia Water Science Center 

Director include the following:

1. Generally overseeing the GaWSC program, including all 

surface-water activities;

2. Ensuring that surface-water activities in the GaWSC meet 

the needs of the Federal Government, the GaWSC, State 

and local agencies, other cooperating agencies, and the 

general public;

3. Ensuring that all aspects of this QA Plan are understood 

and followed by GaWSC personnel, either through direct 

involvement or through clearly stated delegation of this 

responsibility to other personnel in the GaWSC;

4. Briefing subordinates on procedural and technical communications from Regional Offices and Headquarters;

5. Ensuring that all publications and other technical 

communications released by the GaWSC are accurate 

and in accordance with USGS policies; and

6. Implementing USGS and GaWSC safety policies.

Responsibilities of the Chief of the Hydrologic Monitoring 

and Analysis Section (Data Chief) include the following: 

1. Managing the data-collection program by serving as the 

principal contact between cooperators and the GaWSC;

2. Managing the budget to ensure that the data-collection 

program operates in a fiscally responsible manner;

3. Ensuring that surface-water data-collection and analysis 

activities associated with the Georgia streamgaging 

network conform to the goals and policies of the USGS, 

Office of Surface Water (OSW), and GaWSC;

4. Ensuring that any identified deficiencies associated with 

the collection, analysis, or publication of surface-water data 

are corrected and that improved methods are instituted;

5. Developing work plans designed to accomplish the 

work of collecting, processing, analyzing, storing, and 

publishing Georgia surface-water data and communicating the contents of those work plans to personnel in 

the Hydrologic Monitoring and Analysis Section;

6. Ensuring that all personnel in the GaWSC involved in the 

collection, analysis, and publication of surface-water data 

receive a copy of the Surface-Water Quality-Assurance Plan 

and that personnel are familiar with the plan’s contents;

7. Overseeing the production of the GaWSC annual 

data report;

8. Serving as or assigning a Flood and Drought Coordinator;

9. Ensuring that supervised personnel receive 

appropriate training;

10. Ensuring that supervised personnel are current in safety 

training and operate in accordance with safety policies 

established by the USGS and GaWSC as implemented 

by the GaWSC Director;

11. Ensuring that surface-water databases are current and 

properly maintained; and

12. Coordinating activities with the OSW Storm Surge Center 

in Atlanta.

Responsibilities of the Surface-Water Specialist (SWS) 

include the following: 

1. Assuring appropriate methods are used by GaWSC 

personnel in collecting all types of surface-water data; 

2. Performing inspections of individual personnel for 

appropriate field and data-collection procedures;

3. Assuring GaWSC surface-water programs and projects 

are planned to efficiently and effectively provide information required to address high-priority local or national 

water problems; 

4. Collaborating with the Data Chief to evaluate the 

surface-water data-collection and analysis methods 

applied in the GaWSC and determine any needed 

improvements in those methods; and

5. Reviewing all indirect streamflow measurements 

performed by the GaWSC and annually reviewing a 

portion of the surface-water records.

Responsibilities of the Surface-Water Unit Chief (SWUC) 

include the following: 

1. Examining data collected by field personnel for 

completeness, accuracy, and adherence to prescribed 

collection techniques;

2. 2. Providing training in data collection, analysis 

procedures, and instrumentation to individuals assigned 

to the field office;

3. Ensuring that field visitations are scheduled at frequencies 

to allow adequate measurements to facilitate accurate 

computation of streamflow records;

4. Ensuring that supervised personnel are aware of and operate 

in accordance with safety policies established by the USGS 

and GaWSC as implemented by the GaWSC Director;

5. Ensuring that data collected by the unit are computed, 

reviewed, and checked in a timely manner so that data are 

available in final form before the GaWSC annual datareport publication target date;

6. Performing thorough examinations of each employee’s 

data-collection and field procedures to ensure that 

employees possess adequate knowledge of technical 

concepts and demonstrate acceptable practical skills;

7. 7. Ensuring that streamgages are installed in accordance 

with USGS and GaWSC policy;

8. 8. Providing help in troubleshooting malfunctioning 

equipment in the field; and 

9. Overseeing the implementation of new equipment 

deployed in the field.
Collection of Stage and Streamflow Data 3

Responsibilities of the Hydroacoustic Specialist include 

the following:

1. Advising the Data Chief, SWUC, and SWS on all aspects 

of the use of hydroacoustic instrumentation;

2. Updating GaWSC users of hydroacoustic instruments on 

new policies and recommended procedures pertaining to 

the use of those instruments;

3. Updating GaWSC users of hydroacoustic instruments on 

software and hardware upgrades related to the installation 

and use of the instruments;

4. Updating GaWSC hydroacoustic quality-assurance 

documents;

5. Advising the Data Chief on hydroacoustic training 

for personnel;

6. Helping users of hydroacoustic instruments troubleshoot 

malfunctions and take corrective actions;

7. Reviewing data, procedures, methods, and documentation 

regarding hydroacoustics; and

8. Designating specific GaWSC personnel as qualified users 

of hydroacoustic instruments.

Responsibilities of the hydrographers include the following:

1. Ensuring that streamgaging stations operate in a manner 

that minimizes loss of record;

2. Making discharge measurements of various types 

correctly and accurately;

3. Installing, servicing, and repairing instruments at 

streamgaging stations;

4. Storing all data retrieved into the Automated Data 

Processing System (ADAPS) database;

5. Developing ratings, computing records, and writing 

station descriptions and analyses in a timely manner;

6. Helping in constructing streamgaging stations;

7. Surveying station levels, establishing and periodically 

confirming elevations of appropriate reference marks in 

accordance with USGS surveying procedures; and

8. Reviewing real-time data from field stations that are 

accessible on the Web on a daily basis when in the office.

Responsibilities of the Safety Officer include the following: 

1. Assisting the GaWSC Director in implementing USGS 

and GaWSC safety policies; and 

2. Serving as a resource for GaWSC personnel seeking 

current information pertaining to safety.

Overall responsibilities of personnel in Hydrologic 

Monitoring and Analysis Section include the following: 

1. Understanding and following the policies and procedures 

presented in this report; and

2. Collecting, processing, analyzing, storing, and preparing 

surface-water data for publication in accordance with the 

policies and procedures presented in this report.

Collection of Stage and Streamflow Data

Many of society’s daily activities—including industry, 

agriculture, energy production, waste disposal, and recreation—are closely linked to streamflow and water availability; 

therefore, reliable surface-water data are necessary for 

planning and resource management. The collection of streamflow data is a primary component in the ongoing operation of 

streamgaging stations (referred to hereafter as gaging stations) 

and other water-resources studies conducted by the USGS and 

the GaWSC. 

The objective of operating a gaging station is to obtain 

a continuous record of stage and discharge at the site (Carter 

and Davidian, 1968, p. 1). A continuous record of stage, or 

gage height, is obtained by installing instruments that sense 

and record the stream-surface elevation. Discharge measurements are made at periodic intervals to define or verify the 

stage–discharge relation and to define the time and magnitude 

of variations in the relation. 

It is the GaWSC policy that all data-collection activities 

conform with the USGS Water Resources Discipline (WRD) 

guidelines pertaining to the collection of stage and streamflow 

data. All employees involved in surface-water data-collection 

activities are informed of and follow the surface-water datacollection policies and procedures established by the WRD. 

The highest priority in collecting streamflow data, however, is 

employee safety.

Gaging Station Installation and Maintenance

Proper installation and maintenance of gaging stations are 

critical activities for ensuring the quality of streamflow-data 

collection and analysis. Effective site selection, correct design 

and construction, and regular maintenance of a gaging station 

can make the difference between efficient, accurate determinations of drainage-basin discharge and time-consuming, poor 

estimations of flow. 

Site selections for installing gaging stations are determined to meet the intended purpose of each gaging station. 

Additionally, sites are selected with the intent of achieving, 

to the greatest extent possible, ideal hydraulic conditions. 

Rantz and others (1982, p. 5) listed criteria that describe the 
4 Surface-Water Quality-Assurance Plan for the U.S. Geological Survey Georgia Water Science Center, 2010

ideal gaging station. These criteria include unchanging natural 

controls that promote a stable stage–discharge relation, a satisfactory reach for measuring discharge throughout the range of 

stage, and efficient access to the gaging station and measuring 

location. Other criteria considered by GaWSC personnel when 

planning gaging-station installations include those discussed 

in Kennedy (1984, p. 2). 

The individuals responsible for selecting sites for new 

gaging stations are the Data Chief, SWS, and (or) SWUC. 

The process of site selection includes discussions with the 

cooperator(s) on the purpose of the gaging station, analysis 

of the terrain that includes using topographic maps combined 

with field reconnaissance, evaluation of types of installation 

and equipment options, and a file search to determine if 

discontinued stations or partial-record stations previously were 

located in the area. The Data Chief is responsible for ensuring 

proper documentation of agreements with property owners. 

The Data Chief and (or) the SWUC are responsible for 

approval of site design, construction of gaging stations, and 

inspection and approval of the completed installation.

A program of careful inspection and maintenance of 

gaging stations and gage houses promotes the collection of 

reliable and accurate data. Allowing equipment and structures 

to fall into disrepair can result in unreliable data and safety 

problems. Unsightly gaging stations also reflect poorly on the 

public’s perception of the USGS. It is GaWSC policy that a 

visual inspection is performed at sites by field personnel during 

each site visit by comparing inside, outside, and recorder stage 

readings. In addition, all equipment is inspected to ensure 

operational reliability. The inspection of equipment includes 

battery condition, structural stability, locking mechanisms, and 

the general operating condition of the gaging station. Inspection of data-collection equipment at a gaging station is an 

important means of ensuring accurate stage-data records.

To prevent the buildup of mud or clogging of the intakes 

of stilling wells or the orifice of bubbler systems, intakes are 

flushed and orifices are purged at least annually. Stilling wells 

equipped with intakes and flushing devices are flushed during 

each site visit. The goal of the GaWSC is to collect a continuous, complete, and accurate record of stage at each gaging 

station. It is critical that problems resulting in the loss of stage 

record be dealt with immediately.

It is the responsibility of field personnel to correct gaging 

station deficiencies immediately. If conditions cannot be corrected at the site, the immediate supervisor should be notified, 

and that person is responsible for initiating a plan of action to 

restore the stage record at the earliest possible time.

At times, gaging stations are deactivated because of loss 

of funding, a project ending, or gage relocation. Deactivated 

gaging stations that are still important to National, State, 

or local data-collection network goals and potentially still 

usable for data-collection activities are considered inactive 

gaging stations. The GaWSC takes actions necessary to 

protect, secure, and minimize safety hazards at inactive gaging 

stations pending their eventual return to service. Deactivated 

gaging stations that are no longer part of any data-collection 

network or in such state of disrepair that they can no longer 

be activated are considered discontinued gaging stations. The 

GaWSC dismantles discontinued gaging stations and restores 

the land, as much as possible, to previous conditions. The 

GaWSC documents the status of deactivated gaging stations in 

the National Water Information System (NWIS) database. The 

GaWSC also documents deactivated gaging station liabilities 

and cost estimates for remediation in the Discontinued Station 

Maintenance-Capital Improvement (DS-CI) database, which 

can be accessed at http://1stop.usgs.gov/discontinued (WRD 

Technical Memorandum 2009.02). All technical memorandums mentioned in this QA plan are cited in Appendix 1.

Measurement of Stage

Many types of instruments are available, and advances 

in technology continually improve the ability to accurately 

measure water level or stage at gaging stations. Gages can 

be nonrecording or recording gages (Rantz and others, 1982, 

p. 24 and 32, respectively). Because the ways in which stage 

data will be used cannot always be predicted, it is OSW policy 

that surface-water stage records be collected at stream sites 

having instrumentation and procedures to provide sufficient 

accuracy to support the computation of discharge from a 

stage–discharge relation unless greater accuracy is required 

(OSW Technical Memorandum 93.07). The OSW technical 

memorandums from 1969 to present are available online at 

http://water.usgs.gov/osw/.

In general, the operation of gaging stations for the 

purpose of determining daily discharge includes the goal 

of collecting stage data at the accuracy of plus or minus 

(±) 0.02 foot. In cases where lower accuracy is acceptable, the 

project proposal or station description and analysis will state 

why a lower accuracy is being used. An explanation of WRD 

policy on stage-measurement accuracy as it relates to instrumentation is provided in OSW Technical Memorandum 93.07. 

The type of instrumentation installed at any specific gage 

house operated by the GaWSC is dependent on the physical 

site conditions as well as the needs of the cooperator, the availability of utility lines for landline data access, types of terrain, 

expected range of stage, and other factors that can influence 

the data-collection process. Types of data-collection platforms 

(DCPs) currently operated by personnel in the GaWSC include 

Vaisala 555 and Design Analysis H-522. The water-level 

recorders used are Design Analysis H-350, H-350XL, and 

H-510. The devices used to sense stage at Georgia stations are 

H-350/H355 and H-350XL/H-355 bubbler systems; Vaisala 

436B and 436BD shaft encoders; Design Analysis H-510, 

H-334, and H-3341 shaft encoders; and Design Analysis 

H-3611 and H-3612 radar sensors.

The Data Chief or SWUC is responsible for determining 

the types of water-level recorders and the data-collection intervals (typically 15 minute) for operation at each gaging station. 
Collection of Stage and Streamflow Data 5

The Data Chief or SWUC also is responsible for ensuring that 

new equipment has been installed correctly. Field personnel 

who service the gaging station are responsible for maintenance 

or replacement, if appropriate, of gage instrumentation.

Accurate stage measurement requires not only accurate 

instrumentation but also proper installation and continual 

monitoring of all system components to ensure consistent 

accuracy over time (OSW Technical Memorandum 93.07). 

To ensure that instruments located within the gage house 

record water levels that accurately represent the water level of 

the body of water being investigated, “recorder” water-level 

readings are compared to the designated reference gage, as 

described in the station description and(or) station analysis. 

At stilling-well sites, the float-tape pointer serves as the 

reference gage. Readings from the float-tape pointer and shaft 

encoder should always be equal. If these values are not equal, 

the shaft encoder should be reset to the float-tape pointer 

reading. The float-tape pointer should never be reset unless 

levels are run at the site and levels indicate that the float-tape 

indicator is reading incorrectly. At stilling-well sites, other 

gages are installed outside the gage house to indicate whether 

the intakes are operating properly (Rantz and others, 1982, 

p. 53 and 64). Gages installed outside the gage house include 

a wire-weight gage, a staff plate, or a reference point (RP).

At bubbler-system sites, the outside gage serves as the 

reference gage and is used to calibrate the reading of the 

bubbler system. The readings from the bubbler system do 

not always equal outside readings, especially if the gages are 

not in the same pool at all ranges of stage. Whereas bubblersystem and outside gage readings do not have to be the same 

in all cases, the relation between the two for a given stage 

should be consistent. Relations between the two gages across 

a range of stages can be checked for consistency by examining 

form 9-207. Inconsistent readings usually indicate a failure of 

the system, and the system should be investigated. The outside 

gage should not be reset unless levels that are run at the site 

indicate that the outside gage reading is correct. 

Personnel servicing the gaging station are responsible for 

comparing inside and outside gage readings at the beginning 

and end of each site visit to determine if the outside water 

level is represented correctly by the gages. If a deficiency 

is identified, personnel servicing the gaging station are 

responsible for thoroughly documenting the problem in the 

field notes and either correcting the problem immediately or 

contacting the SWUC so that corrective actions can be taken 

at the earliest opportunity. 

Field personnel assigned to the site are responsible for 

ensuring that instrumentation installed at gaging stations is 

properly serviced and calibrated. The SWUC is responsible for 

ensuring that personnel correctly carry out this duty. This is 

accomplished by inspecting gages at the time of installation or 

soon thereafter, discussing field trips and reviewing field notes 

with the less-experienced personnel, and reviewing computed 

records to identify errors or inconsistencies. When deficiencies are identified, field personnel correct the deficiency by 

their own initiative or receive specific instruction from the 

SWUC. Questions related to the calibration and maintenance 

of water-level recorders should be directed to the Data Chief, 

SWUC, and (or) SWS. Standard procedures for documenting corrections to stage data are covered in OSW Technical 

Memorandum 91.09. 

Field personnel are advised to carry spare equipment in 

their field vehicles for most repairs. In the event that repairs 

cannot be made with equipment on hand, field personnel 

should contact the office and advise the SWUC of equipment 

needs for the repairs. Questions related to the calibration and 

maintenance of water-level recorders should be directed to the 

SWUC or Data Chief. When gages are inspected, any recording gage or telemetry gage that differs from the reference gage 

by more than 0.02 foot is reset to agree with the reference 

gage unless a lower accuracy standard has been set and 

documented for that site. Gages should not be reset in adverse 

conditions, such as surging wells, high-flow stages, or ice in 

the stilling well. It is important that bubbler systems not be 

reset during high flow in order to avoid reset errors that may 

be caused by drawdown. 

At stilling wells where data recorders are driven by floats 

with steel tapes, peak-stage indicator clips are attached to steel 

tapes to identify or confirm maximum stages. It is the responsibility of field personnel to inspect gages and ensure peakstage indicator clips are read and reset during each site visit 

and to document clip readings in the field notes. At bubblersystem sites, a crest-stage gage (CSG) should be installed to 

verify peak stage. It is the responsibility of field personnel 

to check the CSG intakes and ground-cork level during each 

gage inspection to ensure that all peaks are recorded.

Most of the basic concepts and procedures used in 

surface-water data-collection activities are presented in three 

chapters of the “Techniques of Water-Resources Investigations 

of the U.S. Geological Survey” (TWRI) series; the chapters 

are entitled “General Procedure for Gaging Streams” (Carter 

and Davidian, 1968), “Stage Measurement at Gaging Stations” 

(Buchanan and Somers, 1968), and “Discharge Measurements 

at Gaging Stations” (Buchanan and Somers, 1969). A number 

of important aspects contained in these references are enumerated and reinforced here. Generally, all surface-water data-collection activities are in accordance with procedures outlined in 

the TWRIs (Hubbard and Barker, 1995). For data-collection 

activities that are not adequately covered by written guidance, 

supervisors assign personnel who have unique experience and 

(or) special training to be fully capable. 

Gage Documents

It is GaWSC policy to have certain documents placed in 

each gage house for the purpose of keeping an on-site record 

of observations, equipment maintenance, structural maintenance, and other information readily available to field personnel. Documents maintained at each gage house include (1) the 
6 Surface-Water Quality-Assurance Plan for the U.S. Geological Survey Georgia Water Science Center, 2010

most recent rating table; (2) a graph of the rating on which 

each new measurement is plotted; (3) the most recent station 

description, including all gages and reference marks at the 

site and associated elevations, locations of measurement cross 

sections, information related to extreme events, including the 

potential for channel storage between the gage and measuring 

section during flood conditions, and other information (see 

the section “Site Documentation, Station Descriptions” in this 

report); (4) a table containing previous discharge-measurement 

information; (5) important telephone numbers; (6) a bridgesafety plan; and (7) a job-hazards analysis. Each gaging station 

is representative of the USGS and, therefore, should be kept 

clean and orderly. Field personnel should clean and sweep 

the gage house during each site visit and keep the gage-house 

exterior and surrounding area neat in appearance. During a 

gage inspection, all gage readings are documented. 

Field personnel who run the field trip are responsible 

for exchanging outdated material with updated gage documents, as needed. When a field person visits a gage house and 

identifies a need to update one or more of the documents, that 

individual makes note of the needed document in the field 

notes and uses this note as a reminder to bring the documents 

on the next field trip. Questions related to which documents 

should be kept in a gage house, when the documents should 

be replaced with newer documents, or appropriate methods of 

appending logs or plotting measurements should be directed to 

the Data Chief or SWUC.

Levels

Various instruments at a gaging station are set to register 

the altitude of the water surface above a selected reference 

level called the gage datum. The gaging station’s supporting 

structures—stilling wells, backings, shelters, bridges, and 

other types of structures—tend to settle or rise as a result of 

earth movement, static or dynamic loads, vibrations, or battering by floodwaters and flood-borne debris. Vertical movement 

of the structure can cause the attached gages to read too high 

or too low and, if errors go undetected, can lead to increased 

uncertainties in streamflow records. Leveling, a procedure by 

which surveying instruments are used to determine the differences in altitude between points, is used to set gages and check 

them from time to time for vertical movement (Kennedy, 

1990, p. 1). Levels are run periodically to all benchmarks, 

reference marks, reference points, and gages at each station to 

determine if datum changes have occurred (Rantz and others, 

1982, p. 545). 

It is GaWSC policy to run levels at newly installed gaging 

stations either at the time of construction or within 6 weeks 

of the beginning date of data collection. Levels are run at 

established gaging stations once every year for the first 3 years. 

After the first three sets of levels are acquired, a level frequency 

of once every 3 years is used. A level frequency of at least every 

5 years is used if stability is shown to exist (Kenney, 2010). 

Gages are reset to agree with levels when the levels indicate 

at least a 0.015-foot vertical change. Level notes are checked 

before the reset is made. When gages are reset, field personnel 

document the reset by including pertinent information in the 

level field notes. The Data Chief or SWUC is notified of the 

reset as soon as field personnel return to the office. 

Field notes identify procedures, specifications, and 

regulations to be followed, describe the unmeasured variables 

that can affect the accuracy and (or) reliability of determinations, indicate any uncertainties or deviations from common 

practice, and report information that could affect the analyses, 

interpretation, or use of the data. For less-structured field 

activities, such as indirect discharge measurements or gagedatum checks, available forms provide only recording space; 

and special effort is required to assure that notes are appropriate, complete, and accurate. 

Level notes need to include a sketch that shows the 

location of reference marks, reference points, outside gage, 

and gage house. Level notes also should contain a clear and 

detailed description of the location of reference marks and 

points. All information is recorded as collected and never 

from memory. 

Levels are run by use of field and documentation methods 

described in Kenney (2010). Level procedures followed by 

GaWSC personnel pertaining to circuit closure, instrument 

reset, and repeated use of turning points are also described in 

Kenney (2010). Level instruments are kept in proper adjustment by appropriate care and handling of equipment. Frequent 

peg tests are performed and documented, and any corrections 

made are noted on the peg-test form using the procedures 

documented in Kenney (2010). A log of peg tests for each 

instrument is kept in each field office, and a copy of the latest 

peg test is kept with the instrument. 

Field personnel and the SWUC are responsible for ensuring that level field notes are checked. Field personnel involved 

in running levels enter the information in the level-summary 

form; this information is checked during station analysis 

procedures for the year. Field personnel and the SWUC are 

responsible for ensuring that levels are run correctly and that 

all level field notes are complete. The SWUC is responsible 

for ensuring that levels are run at the appropriate frequency.

Site Documentation

Thorough documentation of qualitative and quantitative information describing each gaging station is required. 

This documentation, in the forms of station descriptions and 

photographs, provides a permanent record of site characteristics, structures, equipment, instrumentation, altitudes, location, 

and changes in conditions at each site. Information pertaining 

to where these forms of documentation are maintained is 

discussed in the section of this report entitled “Office Setting.”
Collection of Stage and Streamflow Data 7

Station Descriptions

A station description is prepared for each gaging station 

and becomes part of the permanent record for each station. 

One station description is used to detail all data-collection 

activities at that location. It is GaWSC policy that the station 

description is complete by the time the first year’s record is 

computed and analyzed. The field person, SWUC, or Data 

Chief is responsible for ensuring that station descriptions are 

prepared correctly and in a timely manner. The SWUC is 

responsible for ensuring that station descriptions are updated 

as needed and reviewed each year during the annual station 

analysis report process.

Station descriptions are written to include specific types of 

information in a consistent format (Kennedy, 1983, p. 2). Types 

of information included in the station description are location, 

access routes, drainage area, establishment history, cooperator 

identification, reason for cooperation, descriptions of equipment and gaging-station structure, descriptions of control, 

statements on measurement cross sections, information on 

stage extremes, gage datum, elevations of reference marks, and 

a photocopy of an area map. Additional information includes 

information about observers, flow regulation or diversion, 

and anything that will assist in data collection under various 

conditions and ranges of flow. A digital copy of the most 

recent station description for each site is kept in the Site Information Management System (SIMS) on the GaWSC server. 

Photographs

Gaging stations and control sections are documented in 

photographs made by field personnel. Additional photographs 

in the field are taken to document gage-house construction; 

damage to gaging station structures or equipment resulting 

from storms, floods, droughts, or vandalism; significant 

changes in control conditions; or to supplement written 

descriptions. Field personnel carry digital cameras in their 

vehicles as part of their regular field equipment to photograph 

the items mentioned and to document inundated areas, highwater marks, or any other items that may assist the GaWSC 

in data-collection activities.

Historical photographs are filed in the historic-site files. 

Photographs taken with a digital camera are kept on the 

GaWSC server. A site folder for each station is stored in the 

Archive Station Photos folder. Only photographs that are 

important to the gage record are filed.

Direct Measurements

Direct measurements of discharge are made using WRDapproved methods. The GaWSC uses both hydroacoustic and 

conventional current meter methods. 

The hydroacoustic methods used by the GaWSC include 

acoustic Doppler current profilers (ADCPs). The ADCPs 

are used to make discharge measurements at sites that are 

appropriate for the use of ADCPs. The ADCP methods used 

are in accordance with USGS standard procedures and are 

documented by Mueller and Wagner (2009) and in OSW Technical Memorandums 2009.05. Personnel in the GaWSC who 

collect and review ADCP data for discharge measurements 

must have completed the USGS training class “Measurement 

of Streamflow using ADCPs.” The GaWSC has implemented 

a separate QA Plan for hydroacoustics, which includes the use 

of ADCPs for measuring discharge. Appendix C of this report 

contains the GaWSC QA Plan for hydroacoustics.

The GaWSC also uses acoustic Doppler velocimeters 

(ADVs) to make discharge measurements at sites that are 

appropriate for the use of ADVs, and ADV measurements 

are made in accordance with OSW Technical Memorandum 

2004.04 and 2007.01. The use of ADVs also is included in 

the GaWSC hydroacoustics QA Plan, which is contained in 

Appendix C. Personnel using ADCPs and ADVs must read and 

become familiar with the GaWSC hydroacoustics QA Plan.

The GaWSC still uses conventional current meters at 

sites that are not appropriate for the use of hydroacoustic 

methods and to verify discharge measurements made using 

hydroacoustic methods. A conventional current-meter 

measurement is the summation of the subsection areas of the 

stream cross section and their respective average velocities, 

and procedures for making current-meter measurements are 

described in Carter and Davidian (1968, p. 7), Buchanan and 

Somers (1969, p. 1) and Rantz and others (1982, p. 80, 139). 

When personnel make measurements of stream discharge, 

attempts are made to minimize errors. Sauer and Meyer 

(1992) identified sources of errors, including random errors 

such as depth errors associated with soft, uneven, or mobile 

streambeds, or uncertainties in mean velocity associated 

with vertical-velocity distribution errors and pulsation errors. 

Errors also include systematic errors, or bias, associated with 

improperly calibrated equipment or the improper use of such 

equipment. In order to minimize systematic errors, field trips 

are rotated to different personnel every 3 years. 

To ensure and document the accurate performance of 

meters used to make streamflow discharge measurements, the 

GaWSC uses care and maintenance procedures and spin-test 

documentation as recommended in OSW Technical Memorandums 89.07 and 99.06. Individual responsibilities are well 

documented by the memorandum and all persons who make 

current meter streamflow measurements are expected to follow 

the procedures as outlined. The prescribed spin-test logs are 

maintained in the GaWSC field offices.

• Depth criteria for meter selection. GaWSC hydrographers select the type of current meter to be used for 

each discharge measurement on the basis of criteria 

provided by the OSW Technical Memorandum 85.14. 

Meters are used with caution when a measurement 

must be made in conditions outside of the ranges of 

the method provided by OSW. Any deviation from 

the criteria is noted, and the measurement accuracy is 

downgraded accordingly.
8 Surface-Water Quality-Assurance Plan for the U.S. Geological Survey Georgia Water Science Center, 2010

Field personnel should carry a pygmy current meter 

and a Price AA current meter for wading and(or) 

bridge measurements, and these meters are to be maintained and spin tested according to policies described 

in the “Acceptable Equipment” section of this QA 

Plan. For a conventional current meter, the following 

criteria should be followed. A Price AA current meter 

may be used to make direct streamflow measurements 

when depths average 1.5 feet and greater. When depths 

are less than 2.5 feet, a single velocity measurement is 

made at 0.6-foot total depth. When depths are greater 

than 2.5 feet, velocity measurements are made at 0.2- 

and 0.8-foot total depth. 

If bottom velocities are equal to or greater than the top 

velocity, a standard profile does not exist. In the case 

of a nonstandard profile, velocity measurements must 

be made at all three depths—0.2, 0.6, and 0.8 foot. 

When average depths are less than 1.5 feet, the pygmy 

current meter is used. The GaWSC field personnel 

make meter selections for specific measurement conditions based on guidance provided in OSW Technical 

Memorandum 85.14, Buchanan and Somers (1969), 

and Rantz and others (1982). 

In shallow-depth and low-velocity situations, an ADV 

or standard Price AA current meter can be used where 

velocities are too slow to be recorded by the pygmy. 

These situations are to be avoided by looking for cross 

sections where higher velocity occurs. It is recognized, 

however, that at some sites during low-flow periods, 

sections suitable for the pygmy meter cannot be found. 

A measurement made by using a Price AA meter in 

these slow-velocity conditions must be downgraded 

accordingly.

• Number of measurement subsections. The spacing of 

observation verticals in the measurement section can 

affect the accuracy of the measurement (Rantz and 

others, 1982, p. 179). GaWSC criteria require observations of depth and velocity be made at a minimum of 

25–30 verticals, which are normally necessary so that 

no more than 5 percent of the total flow is measured in 

any one vertical. Even under the worst conditions, discharge computed for each vertical should not exceed 

10 percent of the total discharge, and ideally should not 

exceed more than 5 percent (Rantz and others, 1982, p. 

140). Exceptions to this policy are allowed in circumstances where accuracy would be sacrificed if this 

number of verticals were used, such as for measurements during rapidly changing stage (Rantz and others, 

1982, p. 174). Fewer verticals sometimes are used 

for very narrow streams. Measurement of discharge 

is essentially a sampling process, and the accuracy of 

sampling results typically decreases markedly when 

the number of verticals is less than 25. 

• Other direct methods of measuring discharge. It is 

GaWSC policy that WRD and OSW techniques and 

guidelines are followed when discharge measurements 

are made with any selected method. 

• Computation of mean gage height. The GaWSC personnel use the procedures for the computation of mean 

gage height during a discharge measurement presented 

in Rantz and others (1982, p. 170). Mean gage height 

is one of the coordinates used in describing the stage–

discharge relation at a streamflow-gaging site. 

• Check measurements. A second discharge measurement is often made for the purpose of checking an 

initial discharge measurement. If the measurement 

exceeds normal tolerance, a check measurement is 

made, computed, and also checked against the rating 

curve. Normal tolerance is generally within 8 percent. 

However, many streams in Georgia have loose sand 

channel controls and are subject to considerable shifting. Normal tolerance for these streams is within 10 

percent. For extreme flood events, normal tolerance is 

increased to 15 percent. Measurements that are exempt 

from the check-measurement policy are measurements 

made on highly regulated streams where the previous 

measurement conditions no longer exist, are changing 

rapidly, or are expected to change immediately due 

to regulation patterns. Also exempt from the checkmeasurement policy are measurements made where 

changes in the control or obvious changes in the channel are observed. When a discharge measurement is 

made above or below the rating, a check measurement 

is made to verify the rating extension.

When check measurements are made, the potential 

for systematic errors is minimized by using methods 

described in Rantz and others (1982, p. 346). These 

methods include using a different cross-section location for wading measurements, using a different meter, 

using verticals offset from the locations of the original 

verticals used for a bridge measurement, using spintested meters, and using other similar procedures. If the 

initial measurement is made using an ADCP or ADV, 

then the check measurement is made using a conventional current meter when possible.

• Corrections for storage. Corrections for storage applied 

to measured discharges for the purpose of defining 

stage–discharge relations are those discussed in Rantz 

and others (1982, p. 177) and in OSW Technical 

Memorandum 92.09. 

• Questions. Questions concerning the appropriate 

procedures for making stage and discharge measurements should be directed to the GaWSC Data Chief, 

SWUC, and(or) SWS.
Collection of Stage and Streamflow Data 9

Field Notes

Thorough documentation of field observations and 

data-collection activities performed by field personnel are a 

necessary component of surface-water data collection and 

analysis. To ensure that clear, thorough, and systematic notations are made during field observations, field personnel are 

to use Surface-Water Measurement and Inspection (SWAMI) 

electronic forms to record discharge measurements. 

It is GaWSC policy that all discharge measurements 

are to be calculated in their entirety before field personnel 

leave the field site, with the only exception being emergency 

evacuation for reasons of safety. Information required on the 

measurement note sheet includes, at minimum, initials and last 

names of all field-party members; station name; station number; date; times of gage readings and other pertinent observations; gage readings; extreme indicator-clip readings; all items 

describing the type, location, and quality of the measurement; 

control conditions; spin-test comments; cross-section width 

and area; mean velocity; mean gage height; total discharge; 

site identification; and all observed depth and velocity data.

Notations associated with miscellaneous surface-water 

data-collection activities are to be documented on SWAMI 

electronic forms. All miscellaneous notes are required to 

include, at minimum, initials and last names of field-party 

members, station name, station number, date, time of observations, purpose of the site visit, and any descriptive comments 

that field personnel consider applicable and appropriate. 

A review of field notes is required annually when station 

records are computed for each station by both the record 

worker and checker. Deficiencies in the content, accuracy, 

clarity, or thoroughness of field notes are identified and orally 

communicated by the reviewer to the individual who collected 

the field data or to the SWUC. Deficiencies are remedied by 

the SWUC providing specific instructions to the individual(s) 

who failed to record field notations that meet USGS and 

GaWSC standards. 

Acceptable Equipment

Equipment used by the GaWSC to measure surface-water 

discharge meets WRD standards through use and testing. An 

array of standard equipment for measuring discharge includes 

current meters, timers, wading rods, bridge cranes, tag lines, 

and others (Smoot and Novak, 1968; Rantz and others, 1982, 

p. 82). Although an official list of standard equipment is not 

available, Carter and Davidian (1968), Buchanan and Somers 

(1969), and Edwards and Glysson (1988) discuss the equipment typically used by the USGS.

The meters most commonly used by GaWSC personnel for measuring surface-water discharge are the Price AA 

current meter, pygmy current meter, ADCP, and ADV. Methods followed by GaWSC personnel for inspecting, repairing, 

and cleaning these meters are described in Smoot and Novak 

(1968, p. 9), Buchanan and Somers (1969, p. 7), and Rantz 

and others (1982, p. 93). The GaWSC has implemented a 

separate and specific hydroacoustics QA Plan, included as 

Appendix C in the GaWSC surface-water QA Plan. The 

hydroacoustic QA Plan describes the use of ADCPs, ADVs, 

and index acoustic velocity meters.

Field personnel who use the equipment are ultimately 

responsible for the condition and accuracy of the current 

meters (OSW Technical Memorandums 89.07 and 99.06). 

A timed spin test made a few minutes before a measurement 

does not ensure that the meter will not become damaged 

or fouled during the measurement. Field personnel must 

assess apparent changes in velocity or visually inspect the 

meter periodically during the measurement to ensure that 

the meter continues to remain in proper operating condition. 

The GaWSC follows the care and maintenance procedures of 

vertical-axis current meters as described in OSW Technical 

Memorandum 99.06. After a day of use in the field, the pivot 

and contact-chamber cap are removed to clean and lightly 

oil the upper and lower bearing surfaces. Bearing surfaces, 

especially the pivot point, are examined for wear and damage. After cleaning, meter cups are spun to ensure that the 

rotation motion does not have a “wobble” and that cups do 

not come to an abrupt stop. General condition of the meter is 

examined to ensure that cups, tail fins, or other parts are not 

bent or damaged. Any needed repairs are made and significant 

problems are documented in the spin log book. After each field 

trip, meters that were used during the trip are put through a 

timed spin test to document each meter’s condition, and then 

disassembled, inspected, cleaned, and repaired to prepare each 

meter for the next use.

• Spin tests. It is GaWSC policy that timed spin tests are 

required in the office prior to each field trip or at least 

once a quarter. Spin-test results are documented in a 

log that is maintained for each instrument, and all spin 

tests for all current meters are listed in chronological 

order. The log is located in each field office. This log 

is part of the archived data of WRD (OSW Technical Memorandum 89.07). Repairs are made to meters 

when deficiencies are identified during the spin test or 

inspection. The SWUC is required to review this log 

annually. If deficiencies are observed during the review 

of the log, the field person is informed through oral or 

written communication, and the problem is corrected 

immediately. The SWUC performs an overall review 

of the log during annual program review, and field 

personnel promptly correct any deficiencies.

In addition to office-timed spin tests, field personnel are required to perform a field-timed spin test and 

inspect the meter before and after each measurement to 

ensure that the meter is in good condition and that cups 

spin freely and do not come to an abrupt stop. The time 

of the spin test is noted in the appropriate location on 

the electronic (SWAMI) measurement form. Descriptive notations also are made in the appropriate location 

on the SWAMI form concerning meter condition, such 

as “OK” or “free” or other such comments. To ensure 
10 Surface-Water Quality-Assurance Plan for the U.S. Geological Survey Georgia Water Science Center, 2010

that field personnel carry out their responsibilities in 

maintaining the equipment they use, the SWUC or 

SWS inspects the equipment during annual review, and 

field personnel promptly correct any deficiencies.

Alternative Equipment

New or unusual conditions and the development of 

new technology may, at times, involve the collection of 

surface-water data with alternative equipment that has not 

been fully accepted by the USGS. To demonstrate the quality 

of surface-water data collected with alternative equipment, 

thorough documentation of procedures and observations must 

be maintained. 

Indirect Measurements

In many situations, especially during flooding, it is 

impossible or impractical to measure peak discharges by using 

a current meter. Personnel may not receive sufficient warning 

to get to the site to make a direct measurement, or physical 

access to the site during the event may not be feasible. In these 

cases, discharge can be determined by using indirect measurements. The GaWSC Flood Coordinator, assisted by other 

qualified personnel of the Hydrologic Monitoring and Analysis 

Section, oversees indirect measurements of discharge. The 

Flood Coordinator is responsible for seeing that indirect 

measurement computations are made according to appropriate 

TWRI procedures or to recommend alternative procedures 

when established methods are not possible because of unusual 

physical conditions. The GaWSC SWS reviews all indirect 

measurements; and the Regional SWS reviews those made by 

methods that substantially depart from established procedures. 

A peak discharge determined by indirect methods is, 

in many situations, the best available means of defining the 

upper portion of the stage–discharge relation at a site. Because 

extrapolation of a stage–discharge relation, or rating, beyond 

twice the measured discharge at a gaging station is undesirable 

and may be unreliable, discharge measurements made by 

indirect methods during periods of high flows are important 

forms of data (Rantz and others, 1982, p. 334). 

The GaWSC follows data-collection and computation 

procedures presented in Benson and Dalrymple (1967), which 

includes policies and procedures related to site selection, field 

survey, identification of high-water marks, selection of roughness coefficients, computations, and the written summary. The 

GaWSC also follows procedures for measurement of peak 

discharge by indirect methods presented in Rantz and others 

(1982, p. 273). 

In addition to the general procedures presented in 

Benson and Dalrymple (1967), the GaWSC follows guidelines presented in other reports describing specific types 

of indirect measurements suited to particular types of flow 

conditions. The slope-area method is described in Barnes 

(1967) and Dalrymple and Benson (1967). The USGS applies 

the Manning equation in the application of the slope-area 

method (Barnes, 1967). Procedures for selecting the roughness 

coefficient are described in Barnes (1967) and in Arcement 

and Schneider (1989). The computer-based tool, slope-area 

computation (SAC) program, as described in Fulford (1994), 

is available to assist in computations of peak discharge with 

the slope-area method, which is discussed in OSW Technical 

Memorandum 97.01. Procedures for the determination of peak 

discharge through culverts, based on a classification system 

that delineates six types of flow, are described in Bodhaine 

(1982). The computer-based tool, culvert-analysis program 

(CAP), as described in Fulford (1995), is available to assist in 

computations of peak discharge at culverts and is discussed 

in OSW Technical Memorandums 96.04 and 97.01. At sites 

where open-channel width contractions occur, such as flow 

through a bridge structure, peak discharge can be measured by 

using methods described in Matthai (1967) and the WaterSurface Profile Computation (WSPRO) model (Shearman, 

1990). Debris-flow conditions, which are most common in 

small mountainous basins, are discussed in OSW Technical 

Memorandum 92.11. 

Determinations of water-surface profiles along a stream 

channel in association with selected discharges are made 

when studies involve delineations of floodplains or when 

extensions are made to stage–discharge relations at streamflow 

sites. GaWSC personnel are required to follow the procedures 

associated with step-backwater methods described in Davidian 

(1984). The computer-based tool, WSPRO, used for assisting in 

the computations of water-surface profiles with step-backwater 

methods is discussed in OSW Technical Memorandum 87.05. 

General guidelines followed by the GaWSC when making 

indirect measurements include those discussed in OSW Technical Memorandum 92.10 and in Shearman (1990). Violation of 

more than one of the general guidelines does not necessarily 

invalidate an indirect measurement (OSW Technical Memorandum 92.10). The decision to invalidate an indirect measurement 

is based on the application, knowledge, and experience of the 

SWS in reviewing or in computing the measurement. 

The SWS is responsible for ensuring that indirect 

measurements are performed correctly. The SWS or Regional 

SWS is required to review GaWSC procedures and documentation for each indirect measurement before finalizing the 

discharges in any publication or peak-flow files. If deficiencies 

are found during the review, the SWS communicates proposed 

solutions to the person who computed the measurement, and 

that person is responsible for ensuring that corrective actions 

are taken to correct the deficiencies. Specialists outside the 

GaWSC review measurements that are questionable and 

difficult to assess, and the SWS is responsible for ensuring that 

deficiencies identified by the outside party are corrected.

The SWS is responsible for determining when and 

where indirect measurements are made. For the GaWSC, it 

is a general rule that indirect measurements are made at sites 

where the peak flow is estimated to be at least 1.5 times the 

discharge of the greatest measured flow, or when it is essential 

that a peak discharge be determined. Because selection of a 
Collection of Stage and Streamflow Data 11

suitable reach of channel is an extremely important element in 

making an indirect measurement, at some gaging stations the 

stream reach for indirect measurements at specified ranges of 

stage has been preselected, and this information is included in 

the station description. 

Trained personnel are responsible for identifying and 

flagging high-water marks. Because the quality and clarity of 

high-water marks are best soon after a flood, personnel traveling in the field are required to have flagging equipment, such 

as nails and plastic markers, spray paint, paint sticks, survey 

flagging, survey stakes, and other items as needed available in 

the field vehicles. After each indirect measurement is computed, the SWS checks the graphs, field notes and data, plotted 

profiles, maps, calculations or computer output, and written 

analysis associated with the measurement. The information is 

organized into a folder labeled with all pertinent data and filed 

in the station or historical indirect-measurement files.

Peak-Flow Files

The GaWSC is responsible for maintaining the accuracy 

of the peak-flow data files, including computer database files 

(OSW Technical Memorandums 92.10 and 2009.01). The 

SWS is responsible for ensuring that appropriate indirectmeasurement results are entered into the peak-flow files. 

The SWS and the Data Chief are responsible for ensuring 

that peak-flow files are correct. For further discussion on the 

update and review of the peak-flow files, refer to the “Database Management” section of this report.

Crest-Stage Gages

Crest-stage gages are used as tools throughout the WRD 

for determining peak stages at otherwise ungaged sites, 

confirming peak stages at selected sites where recording gages 

are located, confirming peak stages where pressure transducers 

and radar sensors are used, and determining peak stages along 

selected stream reaches or other locations, such as upstream 

and downstream from bridges and culverts. The OSW requires 

QA procedures comparable to those used at continuous-record 

stations for the operation of CSGs and for the computation of 

annual peaks at CSGs (OSW Technical Memorandum 88.07). 

Because of this, the GaWSC has a CSG coordinator to ensure 

continuity of CSG data activities statewide.

The operation of CSGs is part of the GaWSC’s surfacewater program. Procedures followed by the GaWSC in the 

operation of CSGs are presented in Rantz and others (1982, 

p. 9, 77, 78). One or more gages are maintained at each 

selected site where peak water-surface elevations are required. 

Upstream and downstream gages are maintained at culverts or 

other structures where water-surface elevations are required to 

compute flow through the structure and to establish the resulting 

type of flow. CSGs are required at all sites with bubbler systems 

in order to confirm peaks recorded by the bubbler systems.

Except at sites where CSGs are used only to confirm or 

determine peak stages, stage–discharge relations are developed in association with the gage based on direct or indirect 

high-water measurements. Direct or indirect measurements are 

made as site conditions warrant to verify or adjust the rating. 

Levels are run to the gage using the procedures documented in 

Kenney (2010). When extremely high peaks occur, an outside 

high-water mark to confirm the gage reading is obtained when 

possible, described in the field notes, and flagged by a durable 

marker so that the elevation of the high-water mark can be 

determined the next time levels are run. 

Field observations are written on CSG forms or miscellaneous field sheets. All field notes are required to include, at 

minimum, initials and last names of field personnel, the station 

name and number, date, time of observation, current stage, 

CSG reading, and outside high-water mark, if obtained.

The CSG coordinator, SWUC, Data Chief, and SWS are 

responsible for ensuring that correct data-collection procedures 

are used by personnel. Review of data-collection procedures 

and data processing is carried out by each responsible field 

person and the SWUC at least once a year as part of the station 

analysis. When a deficiency in data-collection activities is 

identified, the problem is remedied by proposed solutions communicated by the SWUC to the responsible field person, and 

that person is responsible for ensuring that corrective actions 

are taken to correct the deficiencies. A corrected CSG analysis 

form is kept in the station folder and reviewed by the SWUC 

prior to publication in the annual Water Data Report (WDR). 

Policies and procedures for the computation of peak discharges at CSGs and associated documentation are presented 

in the section entitled, “Processing and Analysis of Stage and 

Streamflow Data.”

Artificial Controls

Artificial controls, including broad-crested weirs, 

thin-plate weirs, and flumes, are built in stream channels for 

the purpose of simplifying the procedure of obtaining accurate 

records of discharge (Rantz and others, 1982, p. 12). Such 

structures serve to stabilize and constrict the channel at a section, reducing the variability of the stage–discharge relation. 

Artificial controls are used at a few gaging stations 

maintained by the GaWSC. In situations where artificial 

controls are installed as permanent structures, it is GaWSC 

policy that stage–discharge relations are determined by making current-meter measurements throughout the range of stage 

at the site if such measurements are practicable and possible. 

If direct methods cannot be used, theoretical methods are used 

and verified by some type of direct measurement, if possible. 

Portable weir plates and flumes are not used currently by 

GaWSC personnel. These portable devices, if used, would be 

applied in accordance with the methods described in Buchanan 

and Somers (1969, p. 57) and Rantz and others (1982, p. 263). 
12 Surface-Water Quality-Assurance Plan for the U.S. Geological Survey Georgia Water Science Center, 2010

The Data Chief and SWS are responsible for ensuring 

the correct design and installation of artificial controls for the 

GaWSC. When installing an artificial control, the GaWSC 

personnel must take into account the criteria for selecting the 

various types of controls, principles governing their design, 

and attributes considered to be desirable in such structures 

(Carter and Davidian, 1968, p. 3; Rantz and others, 1982, 

p. 15, 348; Kilpatrick and Schneider, 1983, p. 2, 44). 

When field inspections of artificial controls are performed, specific information pertaining to control conditions 

is noted on the SWAMI forms to assist in the analysis of the 

surface-water data. These notes include comments concerning 

scour or fill of the streambed immediately upstream from the 

control, leakage, or other pertinent information that could 

affect the accuracy of the artificial control structure. When 

field personnel encounter problems pertaining to artificial 

controls, the SWUC, Data Chief, or SWS should be contacted 

to assist in solving a non-routine problem. 

Flood Conditions

Flood conditions present problems that otherwise do not 

occur on a regular basis. Such problems can include difficulties in gaining access to a gaging station or measuring site 

because roads and bridges are flooded, closed, or destroyed. 

Debris in the streamflow can damage equipment and present 

dangers to personnel during data collection. Rapidly changing 

stage or conditions that necessitate making measurements at 

locations some distance away from the gage can create problems in associating the gage height to a measured discharge.

The GaWSC maintains a Flood Plan to ensure that highpriority surface-water data associated with flooding conditions 

are collected correctly and in a timely manner. The Flood Plan 

describes responsibilities before, during, and after a flood, 

information-reporting procedures, and field-activity priorities. 

The Flood Plan serves as a central reference for emergency 

communications, telephone numbers for key GaWSC personnel, and codes for accessing gaging stations equipped with 

telemetry. 

The Flood Coordinator is responsible for ensuring that 

the Flood Plan includes all appropriate current information. 

Currently, the Data Chief is the designated GaWSC Flood 

Coordinator. The Data Chief and SWS review the Flood Plan 

every 3 years or after a major flooding event. A copy of the 

Flood Plan is provided to all personnel in the Hydrologic 

Monitoring and Analysis Section, as wells as other individuals 

in the GaWSC who assist in surface-water activities. Individuals who receive a copy of the plan keep separate copies in their 

office and in their assigned field vehicle. The Data Chief is 

responsible for ensuring that individuals who receive a copy of 

the plan are fully versed on the content of the Flood Plan. 

During a flood, the Flood Coordinator oversees related 

activities for the GaWSC. A primary responsibility for 

personnel who are not already in the field during flood conditions is to arrive at the office with the intent of going into the 

field for an extended period of time. The Flood Coordinator 

makes field assignments. A primary responsibility for personnel who are already in the field during flood conditions is to 

proceed to make a measurement at the previously selected 

streamflow site and then call the Flood Coordinator to report 

related flood information. Personnel who arrive at a gaging 

station to find that a flood has already peaked are responsible 

for calling the Flood Coordinator to report information about 

flood stage and making a discharge measurement before 

proceeding to find and document high-water marks. GaWSC 

personnel apply methods discussed in Rantz and others (1982, 

p. 60) for determining peak stage at gaging stations.

GaWSC personnel follow policies and procedures 

stated in a number of publications and memorandums when 

collecting surface-water data during floods. Techniques for 

current-meter measurements of flood flow are presented 

in Rantz and others (1982, p. 159–170). Procedures for 

identifying high-water marks for indirect discharge measurements are presented in Benson and Dalrymple (1967, p. 11). 

Adjustments applied to make measured flow hydraulically 

comparable with recorded gage height when discharge 

measurements are made a distance from the gaging station 

are presented in OSW Technical Memorandum 92.09 and 

in Buchanan and Somers (1969, p. 54). All questions about 

particular policies or procedures related to flood activities 

should be directed to the Flood Coordinator and SWUC, and 

personnel who recognize their need for further training in any 

aspect of flood-data collection should consult with the Data 

Chief and SWUC.

The Data Chief and SWS are responsible for reviewing 

GaWSC activities related to floods. This review includes 

ensuring that guidelines and priorities spelled out in the Flood 

Plan are followed and that the guidelines appropriately address 

GaWSC requirements for obtaining flood data in a safe and 

thorough manner. When deficiencies are identified, the Data 

Chief and SWS will remedy them. 

Low-Flow Conditions

Streamflow conditions in Georgia during periods of low 

flow are typically quite different from streamflow conditions 

during periods of medium and high flow. Low-flow discharge 

measurements are made to define or confirm the lower 

portions of stage–discharge relations for gaging stations, as 

part of seepage runs to identify channel gains or losses, and to 

help in the interpretation of other associated data. Additionally, low-flow measurements are made to define the relation 

between low-flow characteristics in a basin and those of a 

nearby basin for which more data are available (OSW Technical Memorandum 85.17). 
Collection of Stage and Streamflow Data 13

In many situations, low flows are associated with 

factors that reduce the accuracy of discharge measurements. 

These factors include algae growth, which impedes the free 

movement of current-meter buckets, and larger percentages 

of the flow moving in unmeasured zones, such as between 

vegetation, at channel edges, and through narrow spaces 

between cobbles. When natural conditions are considered by 

the field personnel to be undependable, the cross section is 

physically improved for measurement by removal of debris 

or large cobbles, construction of dikes to reduce the amount 

of nonflowing water, or other such efforts (Buchanan and 

Somers, 1969, p. 39). If possible, however, channel modification should not be made where it could affect the recorded 

stage at the gage. After modification of the cross section, flow 

should be allowed to stabilize before the discharge measurement is initiated. 

Gage-height of zero flow (GZF) is the gage-height reading at the gaging station when the discharge past the gaged 

location is zero. It is GaWSC policy that GZF measurements 

are made by field personnel during periods of low flow at all 

gages where the low-flow control is recognizable in order 

to make the GZF determinations. A channel control is an 

example of where a GZF measurement generally is not made. 

During extreme drought conditions, stage may fall below 

the recording range of the stage equipment and (or) below 

the stage–discharge relation. The SWUC is responsible for 

ensuring that GaWSC personnel modify equipment in use or 

install new equipment to measure the extremely low stage. 

Also, the SWUC is responsible for ensuring that discharge 

measurements are made at gaging stations where the stage is 

below the stage–discharge relation.

The Data Chief and SWS are responsible for ensuring 

that GaWSC personnel use appropriate equipment and procedures during periods of low flow. Determination by the Data 

Chief, SWUC, or SWS that appropriate procedures are being 

used for data-collection activities during low-flow conditions 

is accomplished by reviewing the low-flow measurements and 

other field activities. The Data Chief and SWUC are responsible answering questions from GaWSC personnel pertaining 

to data collection during periods of low flow.

Cold-Weather Conditions

Surface-water activities occasionally include making 

streamflow-discharge measurements during cold weather 

conditions. Cold temperatures, wind, snow, and ice can create 

difficulties in collecting data. These factors also can create 

dangers for field personnel. The highest priority in collecting 

streamflow data during any season is employee safety. 

At gaging stations where the stream is subject to freezing during winter months, discharge measurements under 

ice cover and during periods of partial ice cover are useful 

for analysis and determination of flow throughout the winter 

period. GaWSC personnel are required to follow the procedures for discharge measurements under ice cover presented 

in Buchanan and Somers (1969, p. 42). This same publication 

includes procedures for discharge measurements made by 

wading or discharge measurements from cableways and 

bridges when debris and ice are in the streamflow. GaWSC 

personnel also follow procedures to collect winter streamflow 

data as presented in Rantz and others (1982, p. 124). Additionally, guidelines on equipment used for measuring flow under 

ice are provided in OSW Technical Memorandum 84.05. 

Presently, OSW views the preferred metering equipment 

for making discharge measurements in slush-free conditions 

under ice cover to be a Price AA current meter modified with a 

Water Survey of Canada winter-style yoke and a conventional 

metal-cup rotor. For conditions where ice slush is present, the 

OSW views the preferred metering equipment to be the Water 

Survey of Canada winter-style yoke with a polymer rotor 

(OSW Technical Memorandum 88.18). Although polymer 

rotors are not allowed (OSW Technical Memorandum 90.01) 

during all other conditions, the superior ability of the polymer 

rotor to shed ice slush and retard freezing in ice-covered 

streams is considered to be more important than the turbulentflow-related inaccuracies associated with the metal rotor 

(OSW Technical Memorandum 92.04). The OSW also views 

the regular AA meters with conventional metal-cup rotors to 

be acceptable for use in slush-free conditions if cutting the 

required larger holes through the ice is feasible (OSW Technical Memorandum 92.04). 

The Data Chief or SWS is responsible for ensuring the 

correct use of equipment and procedures for surface-water 

data-collection activities during winter conditions. This is 

accomplished by ensuring that appropriate equipment and 

procedures are used and by reviewing all field notes immediately following winter field trips, or reviewing field notes 

when station records are reviewed annually.

Storm-Surge Sensor Network

The USGS developed a mobile storm-surge sensor 

network to capture information about the timing, extent, 

and magnitude of storm tides. This mobile network consists 

of 40–70 water-level and barometric-pressure monitoring 

devices that are deployed in the days and hours just prior to 

hurricane landfall. The GaWSC Atlanta office serves as one 

of the USGS’s storm-surge centers, all of which coordinate 

the deployment and recovery of storm-surge sensors and the 

processing and dissemination of the surge data. The Data 

Chief is responsible for coordinating the efforts of the stormsurge center in Atlanta. 
14 Surface-Water Quality-Assurance Plan for the U.S. Geological Survey Georgia Water Science Center, 2010

Processing and Analyzing Stage and 

Streamflow Data

The computation of streamflow records involves 

analyzing field observations and field measurements, determining stage–discharge relations, adjusting and applying 

those relations, and systematically documenting the methods 

and decisions applied. Streamflow records are computed and 

published for each gaging station annually (Rantz and others, 

1982, p. 544). 

This section of the QA Plan includes descriptions of 

procedures and policies pertaining to the processing and 

analysis of data associated with the computation of streamflow 

records. Procedures followed by the GaWSC coincide with those 

described in Rantz and others (1982) and in Kennedy (1983). 

Real-Time Streamflow Data

A necessary and critical element in maintaining accurate 

streamflow records on a real-time basis is the need for rating 

analysis and shift application as soon as practicable after a 

discharge measurement has been made. It is GaWSC’s policy 

that rating analyses and shift applications be performed using 

the following procedures for data to be disseminated on the 

GaWSC’s public Web site http://ga.water.usgs.gov/. 

Real-time data presented on the GaWSC Web site are 

considered to be provisional and subject to revision. Web-site 

users are warned of the inherent limitations of provisional 

data by prominent clickable headings that link to a page that 

explains, in detail, the meaning of the term “provisional data.” 

It is a goal of the GaWSC to process, check, and finalize all 

surface-water records by April 1 of the following water year. 

Additionally, records for the Georgia surface-water network 

(including the provisional application of shifts, gage-height 

corrections, and datum corrections) are up-to-date within 

2 weeks of the most recent field measurement. Recent field 

measurements may indicate the need to correct gage-height 

data or shift the stage–discharge relation, which could lead to 

changes in the provisional data displayed on the Web.

During times of flooding, the use of real-time data is an 

integral part of improving and maintaining stage–discharge 

relations for use in computing streamflow records. The 

GaWSC Flood Plan specifies procedures and responsibilities 

during floods. The Data Chief serves as the Flood Coordinator. It is the responsibility of the Flood Coordinator to 

declare a flood emergency based on the criteria spelled out 

in the Flood Plan. The plan includes a list of high priority 

stations and medium priority stations for which high-water 

measurements are needed to define the upper portion of 

station ratings. The list specifies the gage height above which 

measurements are needed for each site. The real-time data 

on the Web and projected crest estimates provided by the 

National Weather Service are used to help determine to which 

stations and the appropriate time to deploy field personnel. 

It is the responsibility of the Flood Coordinator to direct the 

deployment of field personnel for the purpose of obtaining 

field measurements and for the repair of failed equipment. It 

is the responsibility of the field personnel to call in and report 

measurement data to the Flood Coordinator and to provide 

other pertinent field information. Flood measurements are used 

to update station ratings, shifts, and other aspects of real-time 

discharge computations. Every attempt is made to update this 

information the same day that the measurement information is 

called into the office.

Web-Site Presentation 

Georgia real-time data can be accessed by computers 

from servers located and maintained in the GaWSC 

Atlanta office. The National Water Information System 

Web (NWISWeb) software is used to conform the data to 

national USGS standards. Links to real-time streamflow 

data are displayed prominently on the GaWSC Web site 

http://ga.water.usgs.gov/. By clicking on the phrase “Map of 

current streamflow conditions,” the user can access a map of 

Georgia showing color-coded dots that identify the locations 

of gaging stations equipped with telemetry that provide the 

current streamflow conditions at each site. The user also can 

access a list of Georgia real-time gaging stations grouped by 

river basins by clicking on “Streamflow” at this Web site. 

The GaWSC Web site also contains a direct link to a national 

map that contains color-coded dots that indicate the locations 

of gaging stations across the Country that provide current 

streamflow conditions. The GaWSC Webmaster approves and 

executes any modifications to the GaWSC Web site, whether 

it is the addition or deletion of Web links, the posting of 

USGS publications, or the addition of new Web pages. The 

Webmaster also is responsible for ensuring that the GaWSC 

Web site conforms with all USGS Web and publication 

policies. The GaWSC Director ultimately is responsible for 

approval of all content posted on the GaWSC Web site.

Handling Errors

Two general types of errors are associated with streamflow data that are delivered in real-time and disseminated 

on the Web. The first type of error is the persistent-type 

problem that usually is associated with equipment failure, 

whether in data collection, satellite transmission, or computer 

systems, but this type of problem also could be related to 

weather, such as ice effects. Because of the nature of these 

problems, they generally occur on a continuing basis and 

affect more than a single recording interval. The second type 

of error is the intermittent-type problem that usually results 

in a data-transmission error that shows up either as a zero 

or an unreasonably large value. It is GaWSC policy that 

intermittent-type errors, such as the transmittal of extremely 

large gage-height data, be identified as soon as is reasonably 

possible and the erroneous data either deleted or corrected 
Processing and Analyzing Stage and Streamflow Data 15

as soon as is reasonably possible. For example, if the SWUC 

identifies a data-transmission error during a daily visual check 

of the real-time data, that individual takes immediate actions 

to delete or correct the value and update the real-time Web 

site to display the corrected data. In regard to persistent-type 

problems, it is GaWSC policy not to estimate corrected 

discharges on an ongoing basis during periods of backwater 

caused by the effects of ice. Web users, however, are warned 

about the provisional nature of discharges during winter 

periods. When real-time data on the Web are clearly in error 

for a particular station, possibly because of malfunctioning 

equipment, vandalism at the site, major control damage caused 

by beaver-dam construction, or other similar problems, the 

Data Chief is responsible for deciding when to remove data for 

that particular site from the Web. After repairs have been made 

at the site and the data are determined to be accurate, the Data 

Chief is responsible for deciding when to resume posting the 

real-time data on the Web.

Data-Qualification Statements

The USGS policy regarding the posting of streamflow 

data on the Web is summarized in WRD Technical Memorandum 95.19, which states that streamflow data made available 

on the Web should be considered provisional until the 

formal review process has been completed. To ensure that 

the public who access data from the Web are aware of this, 

data-qualification statements are included at key locations on 

all real-time data Web pages stating Provisional Data Subject 

to Revision. It is GaWSC policy that all GaWSC Web pages 

that contain real-time data, or data that have not been formally 

approved as final, contain a prominent clickable heading that 

links to the following explanations:

Recent data provided by the USGS in Georgia—

including stream discharge, water levels, precipitation, and 

components from water-quality monitors—are preliminary 

and have not received final approval.

Most data relayed in real-time by satellite or other 

telemetry have received little or no review. Inaccuracies in 

the data may be present because of instrument malfunctions 

or physical changes at the measurement site. Subsequent 

review may result in significant revisions to the data.

Data users are cautioned to consider carefully the 

provisional nature of the information before using it for 

decisions that concern personal or public safety or the 

conduct of business that involves substantial monetary or 

operational consequences.

Information concerning the accuracy and appropriate 

uses of these data or concerning other hydrologic data may 

be obtained from the state manager whose name is shown 

on the single station data summary pages, or from the 

USGS SWS in Georgia care of the Webmaster e–mail alias 

Georgia NWISWeb Maintainer.

Measurement and Field Notes

Gage-height and discharge information, control conditions, and other field observations in the electronic SWAMI 

files form the basis for records computation for each gaging 

station. Measurements and field notes containing original data 

are required to be stored indefinitely (Hubbard, 1992). All 

SWAMI files are archived. The archival structure for SWAMI 

files are documented in Appendix B.

Measurements and other field notes that are currently 

being computed for the water year are filed in the primary 

station folder or in the current water year measurement file 

drawer in the office. Measurements and notes for previous 

water years are filed in the office historical files. 

It is GaWSC policy that all measurements are checked. 

For conventional measurements, this includes a check of 

computations and procedures, such as stationing, number of 

sections, use of appropriate equipment, correct gage height, 

and proper transcription of numbers. For measurements computed by using an automated discharge-measurement calculator, only the procedural check is made. The procedural check 

may be done by any Hydrologic Monitoring and Analysis 

Section member other than the field person who made the 

measurement. Measurement information is entered and stored 

in the USGS NWIS database. A printout of the measurement 

list (Kennedy, 1983, p. 12), grouped by year, is included in the 

office technical file in the station-records filing cabinet. 

The person who processes the records for each station 

is responsible for ensuring that the measurement notes are 

correct, the information stored in the computer files agrees 

with the measurement notes, and an updated printout of the 

measurement list is contained in the technical folder.

Continuous Record

Surface-water gage-height data are collected as continuous record (generally at 15-minute intervals) and transmitted 

electronically by satellite or stored in electronic data recorders 

at the site. Streamflow records are computed by converting 

gage-height record to discharge record through the application 

of stage–discharge relations. Ensuring the accuracy of gageheight record is, therefore, a necessary component of ensuring 

the accuracy of computed discharges.

Gage-height record is assembled as completely as 

possible for the period of analysis. Periods of inaccurate 

gage-height data are identified and corrected (see the section 

“Datum corrections, gage-height corrections, and shifts”) or 

deleted as appropriate and as determined by the Data Chief, 

SWUC, or SWS. Items included in the assembly of gageheight record and the procedures for processing the data are 

discussed in Rantz and others (1982, p. 560, 587) and Kennedy (1983, p. 6). 

Immediately following a data-collection field trip, all 

surface-water data loaded onto a computer in the field are 

transferred into ADAPS by using Device Conversion and 

Delivery System (DECODES). Data that are transmitted by 
16 Surface-Water Quality-Assurance Plan for the U.S. Geological Survey Georgia Water Science Center, 2010

satellite are automatically entered into the ADAPS database 

using DECODES. Raw data are maintained unaltered for 

future reference in a file on the data-entry personal computer 

(PC) and on backup tapes as part of a backup system created 

by the GaWSC system administrator. Stage data from the 

primary recorder known to be erroneous can be overwritten 

by correct data obtained from a backup recorder if a backup 

recorder is maintained at the site. 

The person inserting backup record into the primary 

data-descriptor (DD) record is responsible for ensuring that 

correct data are inserted. Any such modification of data should 

be quality controlled, using graphical methods, and noted in 

the station analysis. Stage data stored in the computer files are 

used for computing surface-water records and are compared 

closely with field observations, including observer readings. 

Observer readings are maintained in the designated file drawer 

and are grouped by station. All stage data are to be reviewed 

by the person entering the data, using database graphics 

routines, immediately after entering the data into ADAPS. Any 

problems with the gages should be reported to the SWUC and 

corrected without delay.

Records and Computation

Computation of streamflow data for each station normally 

is computed each year by the field person who is responsible 

for the data-collection activities at the site. Other field personnel check all records for each station by using a records 

computation checklist. Similar procedures are used in each 

field office, and each field office is responsible for setting up 

the necessary office files for storing collected data.

Records-Management System

The status of progress on records computation for each 

gaging station in the State is monitored by using the Records 

Management System (RMS). RMS is a database with an 

internal Web interface that facilitates the documentation and 

tracking of records computation on a sub-water-year basis. It 

stores the comments exchanged among the record processor, 

checker, and reviewer during the record-computation process 

for the period.

Procedures for Processing and Checking Records

Procedures for ensuring the thoroughness, consistency, 

and accuracy of streamflow records are described in this 

section of the QA Plan. Goals, procedures, and policies 

presented in this section are grouped in association with 

the separate components that are included in the recordscomputation process.

Gage Height

The accuracy of surface-water discharge records depends 

on the accuracy of the discharge measurement, accuracy of the 

rating definition, and completeness and accuracy of the gageheight record (OSW Technical Memorandum 93.07). Computation of streamflow records includes ensuring the accuracy 

of gage-height record by comparisons of gage-height readings 

made by use of independent reference gages, comparison of 

inside and outside gages, examination of high-water marks, 

comparisons of the redundant recordings of peaks and troughs 

by use of maximum and minimum indicators, examination of 

data obtained at CSGs, and confirmation or updating of gage 

datum by levels.

Records computation includes examination of the 

gage-height record to determine if the record accurately 

represents the water level of the body of water being monitored. Additionally, it includes identifying periods of time 

during which inaccuracies have occurred and determining 

the cause of the inaccuracies. When possible and appropriate, 

inaccurate gage-height data are corrected. When corrections 

are not possible, erroneous gage-height data are documented 

in writing (station analysis) and removed from the set of data 

being used for streamflow records computation. All missing 

gage-height periods are documented. Specifically, the period 

and the reason for the missing record should be listed in the 

station analysis. It is GaWSC policy to not estimate missing 

gage-height data.

In general, data that accurately reflect stream level should 

be kept. Examples may include backwater from leaves, ice, 

or beaver dams. Stage record that does not reflect stream 

level, such as a float that is stuck, plugged intakes, or a buried 

orifice, should be removed. Periods of mildly lagging intakes 

may be retained in the unit-value record. Also, periods of 

gage-height data when zero flow occurred but the gage pool 

was not dry are retained in the unit-value record.

The person processing the record is responsible for 

clearly identifying periods of erroneous gage-height record 

and deleting erroneous gage-height record from the computer 

file. When data from the primary recorder are replaced by 

data from a backup recorder, the affected periods are to be 

thoroughly documented in the station analysis.

Levels

Errors in gage-height data caused by vertical changes in 

the gage or gage-supporting structure can be measured by running levels. Gages can be reset or gage readings can be adjusted 

by applying corrections based on levels (Kenney, 2010). 

Procedures for computing records and completing level 

information for each gaging station include ensuring that level 

notes are completed for each set of levels, checking level 

notes, ensuring that all shots are balanced correctly, ensuring 

that the level information is listed in the historical levels summary, and ensuring that information was applied appropriately 
Processing and Analyzing Stage and Streamflow Data 17

as datum corrections, or other. The individual computing the 

record is required to check field notes for indications that the 

gages were reset correctly by field personnel. The individual 

computing the records makes appropriate adjustments to the 

gage-height record by applying datum corrections. 

Rating

The development of the stage–discharge relation, also 

called the rating, is one of the principal tasks in computing 

discharge record. The rating is usually the relation between 

gage height and discharge (simple rating). Ratings for some 

special sites involve additional factors, such as rate of change 

in stage, fall in slope reach, or index velocity (complex 

ratings; Kennedy, 1983, p. 14). 

GaWSC personnel follow procedures for the development, modification, and application of ratings that are 

described in Kennedy (1984). GaWSC personnel also follow 

guidelines pertaining to rating and records computation that 

are presented in Rantz and others (1982, chap. 10–14, p. 549) 

and Kennedy (1983, p. 14). 

For each gaging station, the most recent digital rating 

table can be obtained from a printout from the electronic file 

stored in ADAPS, the standard USGS software. In addition, a 

paper copy of the current digital rating is kept in the technical 

folder maintained in the office filing cabinet with the station 

files. A graphical plot of the most recent rating can be obtained 

by generating the graph by using the plotter with standard 

USGS software. When new rating plots are generated to be 

used as the work plots, the previous work plots are discarded. 

Graphical master ratings of all previous numbered ratings are 

retained in the backfile.

The SWUC and other experienced GaWSC personnel 

check and review each rating as part of the annual station 

analysis to ensure accuracy in the development, documentation, and application of each rating. Standard procedures, 

as described in Buchanan and Somers (1969) and Kennedy 

(1984) that pertain to rating development and applications 

are followed in data computations. All measurements are 

plotted on the current rating plot as standard procedure for 

data analysis. When personnel have questions pertaining to 

ratings, the Data Chief, SWUC, or SWS is responsible for 

providing answers. It is GaWSC policy that new ratings are 

checked before copies of the ratings are sent outside the office. 

Significant changes on the upper end of the rating must be 

approved by the Data Chief, SWUC, or SWS. 

Rating Numbering System

Ratings are stored with sequential identification numbers, 

and any modification to rating-input points, including a 

change-of-scale offset, results in a new whole-number rating 

(such as from 12.0 to 13.0). If a rating is extended to a new 

gage height either above or below the current rating, then it 

should be sequenced by a tenth of a whole number (such as 

from 12.0 to 12.1).

The goal of policies and procedures pertaining to ratings 

is to promote efficiency and accuracy in the development and 

documentation of ratings. The person processing the station 

records is responsible for ensuring that all measurements 

for the current year and all high-water measurements for the 

station are plotted on the current work plot of the rating. 

In general, changes in the stage–discharge relation that 

tend to be temporary changes are addressed through the use of 

variable-stage shifts. It is, however, left to the discretion of the 

person working the station records to determine if changes in 

the relation are addressed with shifts or if conditions warrant 

the introduction of a new rating.

In general, changes in the stage–discharge relation that 

are deemed to be relatively stable warrant the introduction of 

new ratings, and well-defined trends also warrant new ratings. 

It is the responsibility of the person processing the records to 

fully develop the new rating; enter all input values and offsets 

into the computer, using standard USGS software; and plot the 

new rating along with the measurement data. 

The person checking the station records is responsible 

for ensuring that the rating-input points and offsets agree with 

available measurement data. The checker has the latitude to 

disagree with the scope and shape of the new rating and with 

the original decision to introduce a new rating. The checker 

also can choose to develop a new rating for the station, if 

appropriate. The checker, however, is responsible for discussing disagreements with the original records processor. The 

two must come to a consensus on the appropriate rating to be 

used. If a consensus is not reached, they are responsible for 

presenting the matter to the Data Chief, SWUC, or SWS for a 

final determination.

Datum and Gage-Height Corrections and Shifts

A correction applied to gage-height readings to compensate for the effect of settlement or uplift of the gage is usually 

measured by levels and is called a datum correction (Kennedy, 

1983, p. 9). Datum corrections are applied to gage-height 

record in terms of magnitude (in feet) and when the datum 

change occurred. In the absence of evidence indicating 

exactly when the change occurred, the change is assumed to 

have occurred gradually from the time the previous levels 

were run, and the correction is prorated with time (Rantz and 

others, 1982, p. 545). Datum corrections are applied when the 

magnitude of the vertical change is greater than 0.015 foot. 

A correction applied to gage-height readings to compensate 

for differences between the recording gage and the base (reference) gage is called a gage-height correction (Rantz and others, 

1982, p. 563). These corrections are applied in the same manner 

as datum corrections by use of the same computer software. 

Gage-height corrections are applied so the recorded data agree 

with reference gage data. These corrections are applied when 

the difference between the recording gage and the reference 

gage is equal to or greater than 0.02 foot.
18 Surface-Water Quality-Assurance Plan for the U.S. Geological Survey Georgia Water Science Center, 2010

A correction applied to the stage-discharge relation, or 

rating, to compensate for variations in the rating is called 

a shift. Shifts reflect the fact that stage–discharge relations 

are not permanent but vary with time, either gradually or 

abruptly, because of changes in the physical features that 

form the control at the gaging station (Rantz and others, 1982, 

p. 344). Shifts can be applied to vary in magnitude with time 

and (or) with stage (Kennedy, 1983, p. 35). Most shifts are 

applied as variable-stage adjustments in GaWSC database 

applications software. Generally shifts are applied if discharge 

measurements plot more than their rated accuracy from the 

rating. Certain factors, however, can affect when and how the 

application is determined, such as stream conditions under 

which the measurement was made. Judgment and experience 

of field personnel are used in shift applications. The SWUC or 

SWS check and review the rating development, application, 

and documentation. Review of each shift application by the 

SWUC or SWS ensures that stage shifts perform as expected. 

The person who processes the station records documents 

the shifts by describing shift magnitude and time of application in the station analysis and by including the shift-analysis 

printout and shift bar-diagram plot with the station analysis. 

Station records also should contain a description of why the 

shift was needed. The shift-diagram points should be plotted on 

a copy of the work rating so that the hydraulic logic of the shift 

curve can be seen. The checker is responsible for ensuring that 

the logic and procedures used in developing and applying the 

shifts are correct and the shifts are documented fully.

Datum corrections, gage-height corrections, and shifts for 

each station are entered in the standard NWIS database and 

are stored as finalized data upon completion of the GaWSC’s 

records-processing work. The person who processes the station record ensures that recorded gage heights and computed 

discharges represent a logical and smooth transition between 

water years. The checker also ensures the quality of the transition between water years. Datum corrections, gage-height 

corrections, and shifts are documented in the station analysis, 

and associated graphs and computer printouts are attached 

to the station analysis as part of the permanent record. This 

documentation is maintained indefinitely for future reference.

Hydrographs

A discharge hydrograph is a plot of daily mean discharge 

in relation to time. The date is aligned with the horizontal axis, 

and the discharge is aligned with the logarithmic vertical axis. 

In the process of computing station records, this hydrograph is 

a useful tool in identifying periods of erroneous information, 

such as incorrect shifts or datum corrections. Additionally, 

hydrographs are helpful when estimating discharges for 

periods of undefined stage–discharge relation, such as during 

backwater or ice conditions, and in estimating discharges for 

periods of missing record. 

Information placed on the hydrograph for each gaging 

station includes, at minimum, the station name and number, 

water year, date the hydrograph was plotted, drainage area, 

plot of daily mean discharge data, plots of measurements, 

indications of datum corrections and shifts, names of the 

gaging stations used for comparison with the hydrograph, 

periods of missing record, estimated discharges for days of 

missing record, periods of ice effect, estimates of discharge 

during periods of ice effect, and the maximum instantaneous 

discharge for the water year. All hydrographs are plotted on a 

standard form with standard log cycles so that the dimensions 

of the graphs are uniform for all gaging stations. 

The person who processes the gaging-station record 

is responsible for completing the hydrograph. The checker 

ensures that the hydrograph is complete and correct. Plots 

typically are printed on the GaWSC’s large-format plotter. 

Hydrograph comparisons assist GaWSC personnel in 

identifying potential problems that may have been overlooked 

in the normal computation procedures (Rantz and others, 

1982). The hydrograph is used in downstream analysis of 

gaging stations in the same or adjacent basin as a tool for 

ensuring the quality of computed discharge record. Hydrographs are filed in the station folder during the computation 

process and are stored in the historical station file when computations for the water year are completed. The Data Chief, 

the SWUC, or the SWS provides guidance when questions are 

raised concerning hydrographs. 

Station Analysis

A complete analysis of the data collected, procedures 

used in processing the data, and the logic used in the computations is documented for each year of record for each gaging 

station, which provides a basis for review and serves as a 

reference if questions arise about the records at some future 

date (Rantz and others, 1982, p. 580). In essence, the station 

analysis tells the “story” of the gage for the year. The use 

of digital photographs is strongly encouraged to help tell 

the “story.” Topics discussed in detail in the station analysis 

include, but are not limited to, equipment, hydrologic conditions, gage-height record (including when and why record is 

missing), datum corrections, rating, discharge, special computations, hydrographic comparison, and remarks concerning the 

quality of records. The person who processes the record writes 

the station analysis. 

The person writing the station analysis must use SIMS 

to construct the analysis. Completed hard copies of the station 

analysis for previous years are grouped in a separate folder 

in the station backfile. Also, an electronic copy of the station 

analysis generated in SIMS is stored on the GaWSC server. 

Included with the hard copy of the station analysis are all 

graphs of variable stage-shift diagrams, a printout of the shift 

analysis, a printout of the year-end summary, and printouts of 

the datum and shift applications. 

The person who processes the station record is responsible for ensuring that the computation is comprehensive and 

complete and that all aspects of the process are documented 

fully in the station analysis and associated material. Likewise, 

the checker is responsible for ensuring that all aspects of the 
Processing and Analyzing Stage and Streamflow Data 19

records-computation process for the station were carried out 

correctly and completely and that the documentation is clear, 

complete, and accurate. 

In the event that the checker disagrees with any of the 

methods or interpretations used, it is the checker’s responsibility to discuss any potential changes with the person who 

processed the station records. It is the responsibility of the 

person who processes the record to make any recommended 

changes proposed by the checker. If a consensus cannot be 

reached between the two parties, it is their responsibility to 

present the issue to the Data Chief or SWUC who will make 

the final determination. 

Winter Records

The GaWSC rarely has ice-affected streamflow data. 

However, on the few occasions when ice forms in stream 

channels or on section controls and causes backwater, the 

stage–discharge relation is affected; the effect varies with the 

quantity and nature of the ice, as well as with the discharge 

(Rantz and others, 1982, p. 360). During some conditions, the 

recorded gage-height data may be accurate, although the actual 

stage-discharge relation may be undeterminable and unstable. 

An example of this condition would be when surface ice forms 

on the stream, but the stilling well remains unfrozen and the 

water level in the stilling well represents the backwater caused 

by the ice in the channel. During other conditions, the recorded 

gage-height data are inaccurate, resulting in periods of missing 

gage-height record. An example of the latter would be when a 

stilling well or the intakes to the stilling well are frozen.

The individual computing the station record is responsible for identifying ice-affected periods and estimating the 

daily discharges during the ice-affected period. The same 

procedures are followed as described in the previous section 

under gage-height corrections and shifts. 

Furnished Record

The GaWSC periodically receives surface-water data collected under the supervision of other agencies, organizations, 

or institutions. When received, these data are published in the 

WDR and may be used in comparison of computed streamflow 

data for specific stations. 

If the GaWSC receives furnished data from other organizations, agencies, or institutions, the data are checked and 

compared with other station data, if possible. The Data Chief, 

SWUC, or SWS is responsible for checking data and assuring 

that data are in conformance with WRD standards. If errors 

in the data are suspected, the furnishing agency is contacted 

to determine if an error was made. The Data Chief, SWUC, 

or SWS is responsible for contacting the furnishing agency. 

Published data from another agency are not normally retained 

as permanent record in the GaWSC database.

Daily-Values Table

With few exceptions, a daily discharge value is determined for each gaging station operated by the WRD and 

stored for each day. The daily-values table generated in NWIS 

represents the discharge values that are stored for each day of 

the water year. 

Daily mean discharge is one of the major products of 

the records-computation process. The person who processes 

the record is responsible for determining that calculated 

daily mean discharges accurately represent actual streamflow 

conditions. That person is responsible for ensuring that the 

daily-values table, which includes the daily values stored 

electronically, contains the correct data. In addition, it is that 

individual’s responsibility to ensure that the correct values 

stored in the daily-values table also are contained in the hydrograph, working primary computations, and the publicationready manuscript. In turn, the checker confirms the accuracy 

of this information. A hard copy of the daily-values table is 

included in the station primary folder. The finalized daily 

values are stored in the NWIS database for future retrieval 

and analysis. The person who processes the record updates the 

progress of the record upon completion of the station record. 

The checker then updates the record progress accordingly 

when the checking process has been completed.

Manuscript and Annual Report

When records computation for the water year has been 

completed, and the data collected and analyzed by GaWSC 

personnel have been determined to be correct and finalized, the 

surface-water data for that water year are published with other 

data in the GaWSC’s WDR. The WDR is part of the series 

entitled “U.S. Geological Survey Water-Data Reports,” which 

can be accessed at http://wdr.water.usgs.gov/. Information 

presented in the WDR includes daily discharge values for the 

year, extremes for the year and period of record, and various 

statistics. Additionally, manuscript station descriptions are 

presented in the WDR. Information contained in the manuscript 

includes physical descriptions of the gage and basin, history of 

the gaging station and data, and statements of cooperation.

In preparing the WDR for publication, the GaWSC follows 

the relevant guidelines presented in Novak (1985) and OSW 

Technical Memorandum 92.07 (summary statistics memo). 

Someone other than the person who computed the record and 

wrote the station analysis checks each station. The SWUC or 

SWS does the final review of the data and publication. The 

Data Chief or SWS checks the proof copy of the report. 

Manuscripts for publication in the WDR are produced 

in SIMS. Tables and graphs of daily values and streamflow 

statistics presented in the report are compiled with the station 

manuscript file using automated computer scripts. Each compiled station file is reviewed. The final compiled file for each 

station is then submitted to the server at USGS Headquarters 

for publication. 
20 Surface-Water Quality-Assurance Plan for the U.S. Geological Survey Georgia Water Science Center, 2010

Instantaneous Data Archive

Instantaneous (unit-value) discharge data are an additional product of the records-computation process. In recent 

years, and particularly since the USGS began making realtime instantaneous data available on NWISWeb in 1994, more 

attention has been given to historical instantaneous discharge 

data, and USGS offices have received increasing requests for 

these data. The Instantaneous Data Archive (IDA), accessible 

at http://ida.water.usgs.gov/, was developed by the USGS 

to provide a means for the public to retrieve instantaneous 

discharge data from the Web. Following completion of the 

WDR each year, the SWS loads the unit-value discharge data 

for the water year into IDA. 

Review of Records

After streamflow records for each gaging station have 

been computed and checked, senior personnel who are chosen 

by the Data Chief review records for all of the GaWSC’s 

gaging stations. The SWS reviews 10 percent of the gaging 

stations, which include complex or nontraditional sites. The 

goals of the review are to ensure that proper methods were 

applied throughout the process of collecting surface-water data 

and computing the record, and to identify areas where further 

training is needed.

If deficiencies are identified during the record review, the 

individuals responsible for compiling the station analysis data 

are notified in writing or verbally. The individuals are responsible for correcting identified deficiencies and re-documenting 

the station data, as necessary. If questions arise concerning the 

validity of the identified deficiencies, the Data Chief or SWS 

resolves the questions.

The Data Chief is responsible for ensuring that any 

deficiencies identified in the review are corrected and that 

actions are taken to prevent recurrence of the deficiencies. 

The Data Chief also is responsible for ensuring that positive 

aspects of the review are communicated to GaWSC personnel 

to recognize good work and reinforce the continued use of 

correct methods and procedures.

Crest-Stage Gages

Records for CSGs are computed with goals and procedures similar to those for other gaging stations. Field notes are 

examined for correctness and accuracy. Peak stages recorded 

by CSGs are cross referenced with other available information; dates of the peaks are determined by analyzing available 

precipitation data and peak data from recording gages within 

the same basin or from nearby basins. 

A discussion on the policies and procedures used in the 

field for collecting data at CSGs is included early in this report 

in the section, “Collection of Stage and Streamflow Data.” 

The discussion in this section describes the analysis and office 

documentation of crest-stage data. This section does not pertain to data collected at CSGs installed solely for the purpose 

of confirming peak stages at sites where pressure transducers 

or radar sensors are used. 

At sites where CSGs are used to compute peak 

discharges, an initial stage–discharge relation, or rating, 

is developed for the site by direct or indirect high-water 

measurements. The rating is verified or adjusted on the basis 

of subsequent direct measurements that are made at least 

every 3 years. Also, a direct measurement is made whenever 

water is on the pipe during a site visit.

For each gaging station, a list of all measurements is 

maintained and each measurement is assigned a chronological 

number. For each station, a graphical plot and table of the 

current rating along with each recent and notably high stagedischarge measurement are contained in each station folder 

and made readily available to those who check and review 

the station record. These data are all stored in the GaWSC 

database. Current station descriptions and a summary of levels 

are maintained in the station folders and in electronic files. 

A brief station analysis is written each year describing the 

computation of the annual peak; identifying the rating number, 

type of rating, and type of flow condition; and describing how 

the dates of the peaks were determined. 

The CSG coordinator, Data Chief, SWUC, or SWS is 

responsible for ensuring the correct computation of annual 

peaks at CSGs. Senior personnel, who are chosen by the Data 

Chief, review CSG computations. When incorrect actions 

or procedures are identified during the review, the reviewer 

informs the person who maintains the site that corrective 

action is needed.

The CSG coordinator is responsible for updating the 

peak-flow file promptly after peak data have been finalized. 

A current listing of annual peaks is maintained in the station 

folder and (or) electronically for review purposes (OSW 

Technical Memorandum 88.07).
Office Setting 21

Office Setting

Maintaining surface-water data and related information 

in a systematic and organized manner increases the efficiency 

and effectiveness of data analysis and dissemination. Good 

organization of files reduces the likelihood of misplaced information; misplaced data and field notes can lead to analyses 

based on inadequate information, with a possible decrease in 

the quality of analytical results. 

This section of the QA Plan includes descriptions of how 

station folders, reference maps, levels documentation, and 

other information related to surface-water data are organized 

and maintained. Additionally, this section provides an overview of how work activities are designed to be carried out 

within the office setting.

Work Plan

The SWUC and chief of each field office, with assistance 

and approval from the Data Chief, assign and schedule routine 

field activities. Trips are run at a frequency that reflects the 

need to define or verify station ratings but are conducted at a 

minimum frequency of every 8 weeks. The workload is based 

on experience and the knowledge of field personnel but is distributed as equally as possible. Beyond normal data-collection 

activities, it is very important that plans be formulated to cover 

extreme hydrologic events. The GaWSC Flood Plan provides 

basic guidance for data-collection activities during flooding 

events. 

The Data Chief, assisted by the SWS, supervises the 

Flood Plan implementation. Low-flow events, by their very 

nature, have lengthy response times and appropriate personnel have ample time to plan field activities tailored to the 

anticipated significance of the event. The exception is a special 

low-flow synoptic run, which requires careful planning and 

logistics. The chief for each field office, with assistance from 

the Data Chief or SWS, almost exclusively directs low-flow 

field activities for relatively minor events. The Data Chief, 

with support from Section personnel, directs low-flow field 

activities for highly significant events.

File Folders for Surface-Water Stations

This section describes the location and content of hardcopy files associated with surface-water data. Information 

pertaining to files maintained electronically can be found in 

the “Database Management” section of this report.

For each gaging station, a separate set of file folders 

is maintained for current and historical data. Current files 

are organized by station number in downstream order, and 

historical files are organized by station number in downstream 

order. Current files are filed in the data section filing area of 

the GaWSC, and historical files are kept in the record section 

filing area of each field office. The set of current files for 

each gaging station contains primary-computation printouts, 

graphed data of stage and discharge, recent measurements, 

current rating, shift and gage-height application sheets, and 

other pertinent data. The set of historical file folders contains 

all previous water data and analyses data for the period of 

record and station description. Extraneous items are removed 

from the current files after the Data Chief determines that 

records are to be finalized for the year. Historical file folders 

from the past 3 years for sites assigned to field offices are filed 

in downstream-order number in those offices and are annually 

transferred to the GaWSC historical files. 

Field-Trip Folders

The GaWSC maintains separate folders for each gaging 

station by field trip or project. The primary purpose of these 

folders is to compile maps, station descriptions, station lists, 

and other pertinent information to allow field personnel to run 

the trips effectively at a moment’s notice and with minimum 

time spent on last-minute preparations. Field personnel are 

responsible for maintaining current information in each gaging 

station folder. 

Level Notes

Recent or current level notes are included in current 

gaging station office folders. When new levels are run, the 

old level notes are moved to the historical measurement 

and field-note files. Level summaries are filed in the current 

station office folder. A copy of the most recent level notes is 

included in the station field folder. All level notes are checked 

for accuracy and proper leveling procedures. Individual field 

personnel, as determined by the SWUC or Data Chief, remedy 

any deficiencies.

Station Descriptions

Surface-water station descriptions are maintained for 

each gaging station in the current and historical office folders. 

Electronic files of station descriptions are maintained in SIMS 

on the GaWSC server by station and water year. Field personnel are responsible for updating and maintaining the station 

descriptions for their assigned areas. The SWUC or Data Chief 

is responsible for ensuring that folders or files are updated. 

Discontinued Stations

File folders for discontinued stations are maintained in 

the historical files by downstream-order number. These station 

folders contain station descriptions, station analyses, ratings, 

daily discharge data, and other pertinent information for each 

water year. 
22 Surface-Water Quality-Assurance Plan for the U.S. Geological Survey Georgia Water Science Center, 2010

Map Files

The GaWSC maintains separate map files for official 

use, which include drainage areas and general topographic 

maps of the State. All maps are organized in alphabetical 

order. Topographic maps are available in scales of 1:24,000, 

and 1:100,000; county maps are available at various scales. 

All maps must remain in the office since these are original 

informational (official) maps used in our operations. Other 

topographic maps are available for general or field use. These 

maps are filed separately from the official maps. The Data 

Chief is responsible for updating information regarding the 

official office maps.

Archiving

All WRD personnel are required to safeguard all 

original field records containing geologic and hydrogeologic 

measurements and observations. Selected materials that are 

not maintained in field offices are placed in archival storage. 

Detailed information on what records have been moved to 

archival centers should be retained in the GaWSC (WRD 

Technical Memorandum 77.83). The types of original data that 

should be archived include, but are not limited to, recorder 

charts and tapes, original and edited data, observer’s notes and 

readings, station descriptions, analyses, and other supporting 

information (WRD Technical Memorandum 92.59; Hubbard, 

1992, p. 12). Electronic data are archived following the policies and guidance in OSW Technical Memorandum 2005.08. 

Appendix B contains the electronic archiving structure used 

by the GaWSC.

Surface-water information is sent to the National 

Archives and Records Administration’s regional Federal 

Record Center (FRC) from the GaWSC as needed and in 

accordance with USGS Records Disposition Schedules, which 

can be accessed at http://www.usgs.gov/usgs-manual/schedule/

index.html. The Data Chief is responsible for deciding what 

information is sent to the FRC, ensuring that the information is 

properly packaged and logged, and verifying that the information has been received by the FRC. The Data Chief maintains 

records in the surface-water section of exactly what has been 

archived. Questions concerning archiving procedures should 

be directed to the Data Chief. Personnel who receive requests 

for information that require accessing archived records should 

contact the Data Chief for assistance.

Revision of Records

When the WDR was published in printed form, revisions 

to discharge records were formalized and documented by 

publishing a revision in the WDR. According to Novak (1985, 

p. 103), these revisions were limited to 

“...only those published records of discharge that 

are substantially in error—and only when the 

revisions are reliable. Revisions may result from 

additional data, re-examination and reinterpretation 

of data, or from the discovery of errors in computation. If revisions are published, an analysis should 

be prepared explaining the basis for making the revisions and the reasons why other periods perhaps do 

not need revision. This analysis should be completed 

and filed for reference.” 

The basic principles guiding revisions described by 

Novak (1985) are still sound and are applied by the GaWSC 

when using electronic databases and publishing formats. 

The GaWSC also uses additional guidance provided in OSW 

Technical Memorandum 2006.05 when revisions of discharge, 

stage, and elevation data are made. 

Communication of New Methods and 

Current Procedures

Personnel who receive training or learn new methods 

or procedures are required to share the information with all 

persons directly involved in tasks that can make use of the 

information. Sometimes the Data Chief, SWUC, or SWS will 

conduct informal training to exchange information to help 

improve the collection and analysis of streamflow data. Any 

new procedure is passed along to each person, either in writing 

or verbally or both. Copies of all memorandums from WRD 

and OSW are given to each employee, and the Data Chief, 

SWUC, and SWS communicate major points to personnel. 

Sometimes memorandums are posted as continuous reminders 

to section personnel. The Data Chief, SWUC, and SWS are 

available to answer questions and discuss procedures. 
Processing and Analyzing Precipitation Data 23

Collection of Precipitation Data

This section of the QA Plan includes descriptions of 

procedures and policies pertaining to the collection of precipitation data. Many of the procedures followed by the GaWSC 

coincide with those described in OSW Technical Memorandum 2006.01.

Rain-Gage Installation and Maintenance

Proper installation and maintenance of rain gages are 

critical activities for ensuring quality in precipitation data 

collection and analysis. The exposure of a rain gage is very 

important for obtaining accurate measurements. Rain gages 

should not be installed at sites that are exposed to excessive 

winds. Rain gages should not be located close to trees, 

buildings, or other structures. A 45-degree cone of clearance 

above the top of the rain gage generally is to be maintained. 

Rain gages should be installed as close to the ground as 

possible without being subject to splash or vandalism. Rain 

gages should also be attached to a sturdy structure that does 

not shake. Rarely will an ideal site be available, and judgment 

must be exercised in choosing an adequate site. 

The Data Chief, SWUC, and (or) SWS are responsible 

for selecting sites for rain gages. The process of site selection 

includes analyzing the terrain by using topographic maps and 

field reconnaissance and evaluating types of installation. The 

GaWSC currently uses Design Analysis H-340 self-calibrating 

tipping-bucket rain gages to collect precipitation data. The 

cumulative (running total) values from the rain gage are 

logged into the DCP every 15 minutes. 

A program of careful inspection, maintenance, and calibration of rain gages promotes the collection of reliable and 

accurate data. Allowing the rain gage to fall into disrepair can 

result in unreliable data. It is GaWSC policy that field personnel perform a thorough inspection of the rain gage during each 

site visit. The inspection includes inspecting 45-degree cone 

clearance; noting the condition of cup, screen, and funnel; 

cleaning the cup, screen, and funnel; and re-leveling the rain 

gage if necessary. In addition, manual test tips are performed 

to ensure the rain gage is working properly. When performing test tips, the rain gage cover is removed, and the bucket 

mechanism is gently tipped 10 times at a rate of about one tip 

every 3 seconds. This is repeated two additional times with 

a time period of about 15 seconds between each set of tips. 

The number of tips from the data logger or field computer is 

recorded in the field notes. If the number of recorded tips is 

not equal to 30, the test is rerun. If the rain gage fails a second 

time, the rain gage is replaced. The rain gage cover should be 

replaced carefully so that erroneous tipping of the bucket does 

not occur. The test tips must then be deleted from the data 

logger or Web site (if transmitted during inspection).

Each rain gage is calibrated at least twice a year using a 

constant head bottle with a nozzle that simulates an intensity 

of 2 inches per hour. The calibration bottle is filled with a 

known volume of water, which corresponds to a specific 

number of inches of rain or number of bucket tips. The 

permissible error range in the number of tips in subsequent 

calibration tests for a particular site must be no more than 

5 percent. If the calibration is found outside the allowable 

range of 5 percent, the instrument is re-leveled and a second 

calibration is performed. If the second rain gage calibration 

test is not within 5 percent, the rain gage is replaced. A rain 

gage that has been removed is then sent back to the manufacturer for re-calibration. Before a calibration test is done, the 

current accumulated precipitation is noted. Once the calibration test is finished, the rain gage is reset to the accumulated 

value observed before the calibration test. The results of the 

calibration test are documented on a tipping-bucket precipitation-sensor test calibration form and filed in the station folder.

Rain-Gaging Station Descriptions

A station description is prepared for each rain-gaging 

station and becomes part of the permanent record for each 

station. It is GaWSC policy that the station description is 

complete by the time the first year’s record is computed and 

analyzed. The station descriptions are compiled in SIMS. The 

field person, Data Chief, or SWUC is responsible for ensuring 

that station descriptions are prepared correctly and in a timely 

manner. The SWUC is responsible for ensuring that station 

descriptions are updated. Station descriptions are reviewed 

each year during the annual station-analysis report process 

and are updated as needed. A digital copy of the most recent 

station description for each site is kept on the GaWSC server 

by year and station.

Processing and Analyzing 

Precipitation Data 

This section of the QA Plan includes descriptions of 

procedures and policies pertaining to processing and analyzing 

data associated with the computation of precipitation data. 

Many of the procedures followed by the GaWSC conform with 

those described in OSW Technical Memorandum 2006.01.

Processing of Real-Time Precipitation Data

It is GaWSC policy that real-time precipitation data 

presented on the GaWSC Web site is considered to be provisional and subject to revision. Web site users are cautioned 

about the inherent limitations of provisional data by providing 

prominent clickable headings that link to a detailed explanation of the meaning of the term provisional data. It is a goal 

of the GaWSC to process, check, and finalize all precipitation 

records by April 1 of the following water year.
24 Surface-Water Quality-Assurance Plan for the U.S. Geological Survey Georgia Water Science Center, 2010

Web-Site Presentation 

Georgia real-time data can be accessed by computers 

from servers located and maintained in the GaWSC Atlanta 

office. The NWISWeb software is used to conform to 

national USGS standards. Links to real-time precipitation 

data are displayed prominently on the GaWSC Web site 

http://ga.water.usgs.gov/. By clicking on the word “Precipitation,” the user can access a list of Georgia real-time 

rain-gaging stations grouped by county. All data from realtime rain gages on the public Web site will be published. 

Any modifications to the GaWSC Web site, whether it is 

the addition or deletion of Web links, the posting of USGS 

publications, or the addition of new Web pages, are approved 

and executed by the GaWSC Webmaster. The Webmaster is 

responsible for ensuring that all GaWSC Web pages conform 

to all USGS Web and publication policies. The GaWSC Director ultimately is responsible for approval of all content posted 

on the GaWSC Web site.

Review of Real-Time Precipitation Data

Real-time precipitation data disseminated on the public 

Web site must be reviewed frequently to ensure data quality 

and to prevent distribution of erroneous information. The 

GaWSC uses both automated and manual review procedures 

to meet this objective. 

The GaWSC has implemented automated procedures 

that include the setting of minimum and maximum threshold 

values and rate-of-change threshold values. If these thresholds 

are exceeded, the automated system initiates warnings of 

potential errors that are displayed on the Georgia real-time 

precipitation Web site. 

In addition to automated procedures, WRD Technical 

Memorandum 99.34 requires frequent and ongoing screening 

and review of data posted on the Web. The GaWSC also 

requires that all Web pages containing real-time precipitation 

data be reviewed regularly for accuracy and (or) missing data. 

The SWUC and field person responsible for the gage scan 

the real-time precipitation data visually each work day. The 

primary goal of the visual check is to identify stations that 

failed to transmit the real-time data and to identify real-time 

data that appear to be erroneous in some way, including a 

clogged rain-gage funnel. When problems with a rain gage 

are identified, the Data Chief or SWUC notifies the person 

responsible for maintaining the gaging station. 

Handling Errors

Two general types of errors are associated with precipitation data delivered in real-time and disseminated on the Web. 

The first type of error is the persistent-type problem that usually 

is associated with equipment failure, whether in data collection or transmission. Because of the nature of these problems 

they generally occur on a continuing basis and affect more 

than a single recording interval. The second type of error is 

the intermittent-type problems that usually results in a datatransmission error that shows up either as a zero or an unreasonably large value. It is the GaWSC policy that intermittent-type 

errors, such as the transmittal of extremely large precipitation 

data, be identified as soon as is reasonably possible and the 

erroneous data either deleted or corrected as soon as is reasonably possible. For example, when the SWUC identifies a data 

transmission error during the daily visual check of the real-time 

data, actions are taken immediately by that individual to delete 

or correct the value and update the real-time Web site to reflect 

the corrected data. When real-time precipitation data shown 

on the Web for a particular station are clearly in error, possibly 

because of malfunctioning equipment, vandalism at the site, 

or other similar problems, the Data Chief is responsible for 

deciding when to remove data from the Web. After repairs have 

been made to the rain gage and the data are determined to be 

accurate, the Data Chief is responsible for deciding when to 

resume posting of the real-time data on the Web.

Continuous Record

Cumulative (running total) precipitation data are collected 

as continuous record (at 15-minute intervals) and transmitted 

electronically by satellite. Precipitation record is assembled for 

the period of analysis in as complete a manner as possible. The 

SWUC or record processor determines and deletes, as appropriate, periods of inaccurate precipitation data. 

Immediately following a data-collection field trip, all 

precipitation data that were loaded onto a computer in the field 

are transferred into ADAPS by using DECODES. Data that 

are transmitted by satellite are automatically entered into the 

ADAPS database using DECODES. Raw data are maintained 

unaltered for future reference in a file on the data-entry PC 

and on backup tapes as part of a backup system created by the 

GaWSC system administrator. Erroneous precipitation data 

from the primary recorder can be overwritten with correct 

data obtained from a backup recorder if a backup recorder is 

maintained at the site. 

The person inserting backup record into the primary 

DD record is responsible for ensuring that correct data are 

inserted. Any such modification of data should be quality 

controlled, using graphical methods. All precipitation data are 

to be reviewed by the person entering the data, using database 

graphics routines, immediately after entering the data into 

ADAPS. Any problems with the gages should be reported to 

the SWUC and corrected without delay.

Records and Computation

The field person who is responsible for the datacollection activities at a gaging station normally computes 

precipitation data for that station. Other field personnel check 

records for each station and track their progress in the RMS. 

Similar procedures are incorporated at each field office. Each 

field office is responsible for setting up the necessary office 

files for storing collected data.
Processing and Analyzing Precipitation Data 25

Procedures for Processing and Checking Records

Procedures for ensuring the thoroughness, consistency, and 

accuracy of precipitation records are described in this section 

of the QA Plan. The goals, procedures, and policies presented 

in this section are grouped in association with the separate 

components that are part of the records-computation process.

Data Corrections

The GaWSC does not apply data corrections to precipitation data. If a calibration test indicates that a rain gage is in 

error by more than 10 percent, the precipitation data recorded 

by that rain gage are removed from the record. 

Estimating Missing Record

The GaWSC does not estimate missing precipitation 

record. If the rain gage is affected by a plugged funnel or 

by snow or ice effects, the data for the affected period are 

deleted and classified as missing. If precipitation data are 

missing for part of a day, the daily sum value for that day can 

be accurately computed as long as values are recorded at the 

00:00:00 time stamp for consecutive days and the rain gage 

accumulator is not reset during this period. In addition, if 

values are missing for consecutive 00:00:00 times, the daily 

sum value for that day can be accurately computed as long as 

no precipitation occurred during the period of missing data. 

Station Analysis

A complete analysis of the data collected, procedures 

used in processing the data, and the logic used in the computations is documented for each year of record for each gaging 

station, which provides a basis for review and serves as a 

reference if questions arise about the records at some future 

date (Rantz and others, 1982, p. 580). Topics discussed in 

detail in the station analysis include, but are not limited to, 

location, equipment, precipitation record (including when 

and why record is missing), computations and calibrations, 

recommendations, and remarks concerning the quality of 

the records. The person who processes the record writes the 

station analysis, which usually is incorporated with station 

analysis for stage and discharge.

The station analysis is constructed by using SIMS. Completed and checked analyses for previous years are grouped in 

a separate folder in the station backfile. The hard copy of the 

analysis, signed and dated by the original record processor and 

the checker, is considered to be a permanent document for the 

station file. Electronic files of the station analysis are stored on 

the GaWSC server by station and water year.

The person who processes the station record is responsible for ensuring that the computation is comprehensive and 

complete and that all aspects of the process are documented 

fully in the station analysis and associated material. Likewise, 

the checker is responsible for ensuring that all aspects of the 

records-computation process for the station were carried out 

correctly and completely and that the documentation is clear, 

complete, and accurate. 

In the event that the checker disagrees with any of the 

methods or interpretations used, it is the checker’s responsibility to discuss any potential changes with the person who 

processed the station records. It is the responsibility of the 

person who processes the record to make the recommended 

changes. If a consensus cannot be reached between the two 

parties, it is their responsibility to present the issue to the Data 

Chief or SWUC who will make the final determination. 

Daily Sum Values Table

Daily sum values are the published product of the 

precipitation records-computation process. The person 

processing the record is responsible for ensuring that the daily 

sum values table, which includes the values stored in the 

daily-values computer file, contains correct data. In turn, the 

checker confirms the accuracy of this information. A hard copy 

of the daily sum values table is included in the station primary 

folder. The finalized daily sum values are stored in the NWIS 

database for future retrieval and analysis. 

Manuscript and Annual Report

When records computation for the water year has been 

completed and the data collected and analyzed by GaWSC 

personnel have been determined to be correct and finalized, 

the precipitation data for that water year are published with 

other data in the GaWSC’s WDR. Information contained in 

the manuscript includes physical descriptions of the gage and 

basin, history of the gaging station and data, and statements 

of cooperation.

Review of Records

After the precipitation records for each station have been 

computed and checked, senior personnel, who are chosen by 

the Data Chief, review records for all of the GaWSC’s raingaging stations. The goal of the review is to ensure that proper 

methods were applied throughout the process of collecting 

precipitation data and computing the record. Comparison 

with nearby rain gages is a critical step in the review of 

precipitation records. If deficiencies are identified during the 

record review, the individual responsible for compiling the 

station-analysis data is notified in writing or verbally. The 

individual is responsible for correcting identified deficiencies 

and re-documenting the station data as necessary. If questions 

arise concerning the validity of the identified deficiencies, the 

Data Chief or SWS resolves the questions.

The Data Chief is responsible for ensuring that any 

deficiencies identified in the review are corrected and that 

actions are taken to prevent recurrence of the deficiencies. 

The Data Chief also is responsible for ensuring that positive 

aspects of the review are communicated to GaWSC personnel 

to recognize good work and reinforce the continued use of 

correct methods and procedures.
26 Surface-Water Quality-Assurance Plan for the U.S. Geological Survey Georgia Water Science Center, 2010

Collection of Sediment Data

Surface-water activities in the GaWSC include the collection, analysis, and publication of sediment data. The GaWSC 

operates in adherence to OSW policies related to sediment data. 

Responsibility for the sediment discipline was transferred 

from the Office of Water Quality (OWQ) to the OSW in 1985 

(OSW Technical Memorandum 92.08). The sediment policies 

and procedures followed by the GaWSC are described in 

selected WRD publications and in memorandums issued by 

OSW, OWQ, and WRD. Techniques adopted by the USGS 

and followed by the GaWSC are presented in Knott and others 

(1992). The GaWSC also follows procedures described in 

three USGS TWRI publications:

1. TWRI book 3, chap. 1: “Fluvial sediment concepts,” 

by Guy (1970); 

2. TWRI book 3, chap. 2: “Field methods for measurement 

of fluvial sediment,” by Guy and Norman (1970); and 

3. TWRI book 3, chap. 3: “Computation of fluvial-sediment 

discharge,” by Porterfield (1972).

 Although no subsequent TWRI chapters have been 

written to officially supersede these three reports, the methods 

presented in Edwards and Glysson (1988) essentially replace 

those presented in TWRI book 3, chap. 2 (WRD Technical 

Memorandum 71.73; OSW Technical Memorandums 88.17, 

93.01). Additional guidance on sediment sampling methods 

also is provided by Nolan and others (2005).

A summary of memorandums issued since 1971 

related to sediment and sediment transport is provided in 

OSW Technical Memorandum 92.08. A summary of documentation that describes instrumentation and field methods 

for collecting sediment data is provided in OSW Technical 

Memorandum 93.01.

Sampling Procedures

Suspended-sediment data are collected by GaWSC 

personnel by using sampling methods that include the 

single vertical method, the equal-discharge increment (EDI) 

method, the equal-width increment (EWI) method, and the 

point-sample method. For installation and use of automatic 

pumping-type samplers, the GaWSC personnel follow the 

criteria described in Edwards and Glysson (1988, p. 26-34). 

Field methods for sediment sampling are documented in 

OSW Technical Memorandum 93.01. Water samples obtained 

for the analysis of sediment concentration and particle size are 

not composited (OWQ Technical Memorandum 76.17; OSW 

Technical Memorandum 93.01). The cone splitter is used for 

samples that are split (OWQ Technical Memorandum 80.17). 

If the total suspended solids (TSS) analytical method is used 

to determine suspended-sediment concentration (SSC) in a 

stream, it is GaWSC policy to develop a relation between SSC 

and TSS by using the guidelines in OSW Technical Memorandum 2001.03 to compute SSC. 

Guidelines for the collection and publication of bedload 

data are provided in OSW Technical Memorandum 90.08. This 

memorandum supersedes policy and guidelines previously 

provided in OWQ Technical Memorandums 76.04, 77.07, 

79.17, and 80.07, as well as in WRD Technical Memorandum 77.60. Among the policies stated in OSW Technical 

Memorandum 90.08, which are followed by the GaWSC, is 

one stating that three cross-sectional methods are used for 

bedload sampling—the single equal-width increment (SEWI) 

method, the multiple equal-width increment (MEWI) method, 

and the unequal-width increment (UWI) method. Additionally, it is stated in OSW Technical Memorandum 90.08 that 

field personnel are responsible for selecting the procedure 

that is optimal for the local condition. Bedload samples are 

analyzed individually in some situations and as a composite 

in other situations. Until sampling variability for a particular 

site is understood by those analyzing the data, all samples are 

required to be analyzed individually. 

Project personnel involved in sediment-related hydrologic 

investigations are responsible for scheduling sedimentcollection activities at specific sites. The SWS is responsible 

for ensuring that GaWSC personnel use correct procedures to 

collect sediment data. The SWS establishes whether or not correct procedures are being used by conducting periodic reviews 

of sediment field trips, sample processing, and records computation. Qualified staff remedy deficiencies through in-house 

training. Questions concerning sediment-sampling techniques 

should be directed to the SWS or other qualified personnel who 

have proper training in sediment-related disciplines.

Field Notes

It is GaWSC policy that personnel must fill out note sheets 

each time a site is visited for the purpose of sediment sampling 

and complete the note sheet in its entirety before leaving the 

site. Original observations written on the note sheets are not 

to be erased; data are corrected by crossing out the original 

observations and writing the correct information near the original 

value. The goal of placing information on the field note sheet is to 

describe the equipment and methods used during the site visit as 

well as to describe relevant conditions or changes (OSW Technical 

Memorandum 91.15). For each site visit, information included 

on the note sheet includes, at minimum, the site identification, 

field personnel name(s), date, time, sampling equipment, and 

method, as covered in OSW Technical Memorandum 91.15. 

Upon completion of each field trip, field notes are placed 

in office files for future reference. Data section personnel, 

other than those who collected the sediment samples, check 

the field notes.
Collection of Sediment Data 27

Equipment Use, Care, and Maintenance

Field personnel who use sediment-sampling equipment 

are responsible for the care and maintenance of the equipment. 

Major parts replacement and repair of damaged equipment are 

accomplished through contracts with the Federal Interagency 

Sedimentation Program (FISP) in Vicksburg, Mississippi. 

Minor repairs are made in-house by qualified personnel. The 

SWS and project personnel are responsible for ensuring that 

appropriate equipment is used at all sampling sites. Sampling 

equipment is selected based on the constituents being investigated, the type of analyses that are to be performed, and the 

site conditions, including velocity and maximum depth of the 

water. The GaWSC follows equipment-design criteria and 

guidelines referenced in OSW Technical Memorandum 93.01. 

Sample Handling and Storage

The quality of sediment data provided by a sediment 

laboratory is affected by the quality of the samples received 

from the field (Knott and others, 1993, p. 2). The GaWSC 

personnel are required to prepare sample labels, analysis 

instructions, and sample documentation according to guidelines presented in Knott and others (1993). 

Sediment-sample containers and sediment samples are 

stored in the GaWSC on-site warehouse. Samples are shipped 

to the appropriate laboratory for sediment analysis. Because 

sediment-sample containers are glass, they are securely 

taped and packed for shipment in foam-filled plastic crates 

to minimize the risk of breakage. 

High-Flow Conditions

High-flow conditions at most streams, unless the streams 

are subject to the effects of backwater, are associated with 

high-energy conditions. The sediment flux and particle sizes 

associated with high flows are important factors in sediment 

studies conducted by the GaWSC. To ensure that field personnel are aware of their responsibilities in obtaining sediment 

samples at appropriate sites during high-flow conditions, the 

project and section chiefs involved in sediment studies provide 

a list of sediment-sampling sites and sampling requirements to 

appropriate field personnel. These individuals are responsible for 

ensuring that sediment samples are obtained during opportunities provided by high-flow events and for ensuring that proper 

sampling equipment and methods are used during high-flow 

conditions The SWS and qualified project personnel are responsible for answering questions from GaWSC personnel concerning high-flow sampling equipment or sampling procedures. 

Cold-Weather Conditions

Sediment-sampling activities in the GaWSC occasionally include obtaining samples during periods of subfreezing 

temperatures. During cold-weather conditions, field personnel 

should take every precaution to ensure their personal safety. 

Additionally, field personnel should attempt to ensure that 

equipment is not damaged by floating slabs of ice and that 

nozzles are not clogged with ice crystals. 

When floating slabs of ice pose a danger of damaging 

sampling equipment, such as during spring thaw, field personnel may be able to obtain only surface samples between the 

floating slabs of ice (Edwards and Glysson, 1988, p. 86). 

This procedure is noted on the field note sheet and sample 

label. When anchor ice and frazzle ice are present, it may be 

necessary to move the sampling equipment quickly through 

ice crystals to avoid clogging the nozzle. This procedure is 

also noted on the field note sheets and sample label. 

Site Documentation

A station description is prepared for each new sedimentsampling site. At sampling sites where streamflow-gaging 

activities occur, the description of sediment activities is 

included in the streamflow-gaging station description in SIMS. 

A list of elements included in each station description with 

an explanation of the items included with each element is 

presented in the attachment to OSW Technical Memorandum 

91.15. At sites where only sediment samples are collected, 

the station descriptions are structured similarly to those for 

streamflow-gaging stations and contain similar informational 

items (Kennedy, 1983, p. 2). At sampling sites where gage 

houses have been installed, station descriptions are kept in 

the gage house to provide field personnel with information 

pertinent to sediment-sampling procedures for that particular 

site. Station descriptions and the five most recent station 

analyses are included in the field folder and are maintained in 

the office files. Each description includes specific information 

explaining where the samples are to be collected and what 

method is to be used. Recent station analyses contain pertinent 

information about the sampling conditions and problems that 

may have been encountered recently.

Field personnel assigned to regularly run specific field 

trips are responsible for ensuring that field copies of station 

descriptions and recent station analyses are located at gage 

houses and kept current. The individual who processes the 

sediment-station data keeps station descriptions current by 

periodic review and updates. The section chief, or qualified 

project personnel, reviews station descriptions and analyses 

to ensure that they are current. These reviews are made at 

least once each year. When a deficiency is identified during 

the review of station descriptions or analyses, the responsible 

person corrects and documents the deficiency. 

At sampling sites with gage houses, logs of sampling 

activities are maintained. The information recorded in these 

logs includes the names of individuals who conducted the 

sampling, dates and times of sample collection, and the project 

for which the samples were collected.
28 Surface-Water Quality-Assurance Plan for the U.S. Geological Survey Georgia Water Science Center, 2010

Processing and Analysis of 

Sediment Data

Sediment and associated streamflow data are compiled to 

produce sediment records for specific sites. Data processing 

of periodic measurements consists of four steps: tabulation, 

evaluation, editing, and verification (OSW Technical Memorandum 91.15). The GaWSC follows the considerations and 

guidelines presented in Guy (1969), Porterfield (1972), and 

OSW Technical Memorandum 91.15 in carrying out these 

four steps. The GaWSC follows the guidelines and procedures 

outlined by Rasmussen and others (2009) when computing 

sediment concentrations using surrogates, such as turbidity or 

streamflow (OSW Technical Memorandum 2010.01).

The SWS and qualified project personnel are jointly 

responsible for ensuring that appropriate procedures are 

applied correctly in processing sediment data. During the 

time the sediment data are being processed for the year by 

qualified personnel, field notes and work sheets for each site 

are maintained in appropriate office files. After the record has 

been completed, field notes and work sheets are maintained in 

office archive files. 

Sediment Laboratory

The GaWSC has a sediment laboratory, which accommodates limited sediment analyses. If a more detailed sediment 

analysis is needed, the samples are shipped to the appropriate 

laboratory for analysis. 

Sediment-Station Analysis

A sediment-station analysis is written in SIMS for each 

sediment station operated by the GaWSC each water year. 

The sediment-station analysis is a summary of the sediment 

activities at the station for a given year. The analysis includes 

the hydrograph coverage of sampling, the types of samples 

collected and sampling procedures used, changes that might 

affect sediment transport or the record, and the methods and 

reasoning used to compute the record. Information included 

in the sediment-station analysis is presented in a thorough 

manner that enables the checker and reviewer to determine, 

from the analysis, the adequacy of the activities in defining the 

record and accomplishing the objectives defined for the station 

(OSW Technical Memorandum 91.15). 

Elements included in each sediment-station analysis 

are listed in OSW Technical Memorandum 91.15, including 

descriptions of the elements and examples. Station analyses 

are filed in appropriate office files by project personnel and are 

backfiled every 5 years. 

Sediment-Analysis Results

Sediment concentration, sand-silt split, and particle-size 

data are published in the WDR and also in open-file and 

interpretive project reports when appropriate.

Sediment-Data Storage

Sediment data collected for the GaWSC are stored both 

in paper files and in the NWIS Water-Quality (QWDATA) subsystem (OSW Technical Memorandum 2004.01; OSW Technical Memorandum 2010.03). Those responsible for ensuring 

that the data are processed properly and maintained include 

the SWS, project personnel, and database administrators. 

Paper and computer-file records are reviewed on an annual 

basis, and any discrepancies are resolved among these people.

Database Management

The overall process of storing surface-water data collected at continuous-record gaging stations includes electronic 

entry of the unit-value stage data by using NWIS, the standard 

USGS national database; computing corresponding discharge 

values; computing daily mean discharges based on the unit 

discharges; and storing the daily means in the NWIS database. 

In addition, the instantaneous annual peak discharges, associated peak gage heights and peak discharges above base, and 

the associated gage heights are determined for each gaging 

station and stored in the peak-flow file. 

Ultimately, the Data Chief is responsible for ensuring that

surface-water data files are updated and accurate. The Data Chief

also oversees all aspects of data entry and data management.

The field person who collects the unit-value data is 

responsible for entering the data electronically. Depending on 

the equipment used at each site, the data generally are entered 

manually, automatically by satellite, or by downloading electronically recorded data on a personal computer or data card. 

The Data Chief can delegate the task of entering the 

unit values electronically to individuals other than those 

who collect the original data. The person who computes the 

records is responsible for ensuring that the correct data are 

contained in the appropriate files for each gaging station and 

for ensuring that the correct daily mean discharges are stored 

for each station. 

A second individual independently checks to see that the 

appropriate data are contained in appropriate computer files 

for each station. The Data Chief assigns a specific individual 

to be responsible for maintaining the local computer programs 

and files and for updating the national database.
Publication of Surface-Water Data 29

The SWS is responsible for updating the peak-flow file 

and ensuring that the data are correct. After streamflow records 

for a water year have been computed and checked and the data 

have been finalized, the SWS ensures that the peak-flow file 

is updated to include the published peak discharges and gage 

heights for each gaging station for the water year. Following 

the computer-update procedure, the SWS ensures the correctness of the data by comparing all stored values for the year 

with the published values. 

Publication of Surface-Water Data

The act of Congress (Organic Act) that created the U.S. 

Geological Survey in 1879 established the Survey’s obligation 

to make public the results of its investigations and research 

and to perform, on a continuing, systematic, and scientific 

basis, the investigation of the geologic structure, mineral 

resources, and products of the national domain (U.S. Geological Survey, 1986, p. 4). Fulfilling this obligation includes the 

publication of surface-water data and interpretive information 

derived from the analyses of surface-water data.

Publication Policy

The USGS and WRD have specific policies pertaining to 

the publication of data and interpretations of data. All WRD 

personnel, including those of the GaWSC, are required to 

adhere to these policies. A brief summary of goals, procedures, 

and policies is presented in U.S. Geological Survey (1986, 

p. 4–37). 

All information obtained through investigations and 

observations by the staff of the USGS or by its contractors 

must be held confidential and not be disclosed to the public 

until the information is made available to all, impartially and 

simultaneously, by approval of the USGS Director. In some 

cases, approval for release of information to the public is 

delegated to the area regional executive (REX) or to the local 

Science Center Director. Data and interpretive information 

is released by formal publication or other means of public 

release, except to the extent that such release is mandated by 

law (U.S. Geological Survey, 1986, p. 14). With delegated 

approval, hydrologic measurements resulting from observations and laboratory analyses that have been reviewed for 

accuracy by designated WRD personnel are excluded from 

the requirements to hold unpublished information confidential 

(U.S. Geological Survey, 1986, p. 15). 

All interpretive writings in which the USGS has a 

proprietary interest—including abstracts, letters to the editor, 

and all writings that show the author’s title and USGS affiliation—must be approved by the USGS Director for release to 

the public. The objectives of the approval review are to finalcheck the technical quality of the writing and to make certain 

that it meets USGS publication standards and is consistent 

with policies of the USGS and Department of the Interior. 

Approval by the Director or the Director’s designee ensures 

that each publication or document (1) is impartial and objective, (2) has conclusions that do not compromise the USGS’s 

official position, (3) does not take an unwarranted advocacy 

position, and (4) does not criticize or compete with other 

governmental agencies or the private sector (U.S. Geological 

Survey, 2006a). 

Types of Publications

Various types of USGS publications are available in 

which surface-water data and data analyses are presented. 

Publications in the USGS series include Professional Papers, 

Scientific Investigations Reports, Scientific Investigations 

Maps, Data Series, Techniques and Methods (replaces 

the TWRIs), Circulars, Fact Sheets, General Information 

Products, Open-File Reports, and Administrative Reports 

(U.S. Geological Survey, 2003, app. A). Water-resources 

data, including surface-water data collected by the GaWSC, 

are published annually in the Water Resources of the United 

States—Water Data Report (also referred to as the annual data 

report, or ADR). Currently, the report is accessible online at 

http://wdr.water.usgs.gov/. Factors considered by the GaWSC 

personnel when choosing the appropriate publication series to 

use in presenting various types of information are presented in 

U.S. Geological Survey (2003).

Review Process

The USGS procedures for publication and requirements 

for manuscript review are summarized in U.S. Geological 

Survey (2009). It is GaWSC policy to adhere to the USGS 

requirements for review and approval of reports prior to 

release to the public. At least two technical reviews are 

required for each report (U.S. Geological Survey, 2006b). 

Competent and thorough editorial and technical reviews are 

the most certain ways to improve and assure the high quality 

of the final report. Principles of editorial review and responsibilities of reviewers and authors are presented in Moore and 

others (1990, p. 24–49).
30 Surface-Water Quality-Assurance Plan for the U.S. Geological Survey Georgia Water Science Center, 2010

Safety

Performing work activities in a manner that ensures the 

safety of personnel and others is of the highest priority for the 

USGS and the GaWSC. Beyond the obvious negative impacts 

that unsafe conditions have on personnel, such as accidents 

and personal injuries, unsafe conditions also can have a 

negative effect on the quality of surface-water data and data 

analysis. For example, errors are more likely to be made when 

an individual’s attention to important details is compromised 

by dangerous conditions. To help personnel be aware of and 

follow established procedures and policies that promote 

all aspects of safety, the GaWSC communicates current 

information and directives related to safety to all personnel by 

in-house training classes, memorandums, and online training 

courses. Specific policies and procedures related to safety can 

be found in the GaWSC Safety Plan. The Safety Officer is 

responsible for ensuring that each employee reads and familiarizes himself or herself with pertinent safety memorandums 

or manuals and attends required training classes. The GaWSC 

also has a Safety Committee that is composed of representatives from different sections of the GaWSC Questions or 

concerns pertaining to safety, or suggestions for improving 

safety, should be directed to either the Safety Officer or the 

Safety Committee. 

Training

Ensuring that the GaWSC personnel obtain knowledge of 

correct methods and procedures is a vital aspect of maintaining 

the quality of surface-water data and data analysis. Providing 

appropriate training to GaWSC personnel increases the quality 

of work and eliminates the source of many potential errors. 

Much of the training provided to GaWSC personnel is onthe-job training provided as a form of mentoring. On-the-job 

training for new employees is standard protocol. Designees 

of the Data Chief teach acceptable field practices. In all cases, 

instructors are experienced and knowledgeable concerning 

prescribed techniques and proper procedures. Data collected 

by inexperienced field personnel are closely examined for 

completeness, accuracy, and adherence to prescribed collection techniques by the SWUC and designated members of the 

Hydrologic Monitoring and Analysis Section. The intensity of 

the examinations remains at a high level until such time as the 

employee is deemed to possess a thorough knowledge of the 

technical concepts and demonstrates acceptable practical skills.

Other types of training pertaining to data-collection and 

analysis procedures are accomplished by in-house training by 

supervisors or specialists, regional training courses, online 

training courses, or training courses through the USGS 

National Training Center. The goal of this type and all types 

of training is to ensure that field and office activities are 

performed in accordance with specified OSW and WRD 

standard practices and policies, and that these activities are 

performed by adequately qualified, experienced, and supervised personnel. 

Requests for training and career-enhancement opportunities are discussed at least annually with individuals. The 

GaWSC Training Officer determines training needs and 

requests formal training. Each employee receives notifications 

of regional and national training courses that are available 

each year. Training courses completed by employees are 

documented in the Department of Interior’s Learning Management System (DOI Learn). 
References Cited 31

References Cited

Arcement, G.J., and Schneider, V.R., 1989, Guide for selecting 

Manning’s roughness coefficients for natural channels and 

flood plains: U.S. Geological Survey Water-Supply Paper 

2339, 38 p. 

Barnes, H.B, 1967, Roughness characteristics of natural channels: U.S. Geological Survey Water-Supply Paper 1849, 3 p. 

Benson, M.A., and Dalrymple, Tate, 1967, General field and 

office procedures for indirect discharge measurements: U.S. 

Geological Survey Techniques of Water-Resources Investigations, book 3, chap. A1, 30 p. 

Bodhaine, G.L., 1982, Measurement of peak discharge at 

culverts by indirect methods: U.S. Geological Survey Techniques of Water-Resources Investigations, book 3, chap. A3, 

60 p. 

Buchanan, T.J., and Somers, W.P., 1969, Discharge measurements at gaging stations: U.S. Geological Survey Techniques of Water-Resources Investigations, book 3, chap. A8, 

65 p. 

Buchanan, T.J., and Somers, W.P., 1968, State measurement 

at gaging stations: U.S. Geological Survey Techniques of 

Water-Resources Investigations, book 3, chap. A7, 38 p.

Carter, R.W., and Davidian, Jacob, 1968, General procedures 

for gaging streams: U.S. Geological Survey Techniques of 

Water-Resources Investigations, book 3, chap. A6, 13 p. 

Dalrymple, Tate, and Benson, M.A., 1967, Measurement of 

peak discharge by the slope-area method: U.S. Geological Survey Techniques of Water-Resources Investigations, 

book 3, chap. A2, 12 p. 

Davidian, Jacob, 1984, Computation of water-surface profiles 

in open channels: U.S. Geological Survey Techniques of 

Water-Resources Investigations, book 3, chap. A15, 48 p. 

Edwards, T.K., and Glysson, G.D., 1988, Field methods for 

measurement of fluvial sediment: U.S. Geological Survey 

Open-File Report 86–531, 118 p. 

Fulford, J. M., 1994, User’s guide to SAC, a computer program for computing discharge by slope-area method: 

U.S. Geological Survey Open-File Report 94–360, 31 p. 

Fulford, J. M., 1995, User’s guide to the culvert analysis 

program: U.S. Geological Survey Open-File Report 95–137, 

35 p. 

Guy, H.P., 1969, Laboratory theory and methods for sediment 

analysis: U.S. Geological Survey Techniques of WaterResources Investigations, book 5, chap. C1, 58 p. 

Guy, H.P., 1970, Fluvial sediment concepts: U.S. Geological Survey Techniques of Water-Resources Investigations, 

book 3, chap. C1, 55 p. 

Guy, H.P., and Norman, V.W., 1970, Field methods for 

measurement of fluvial sediment: U.S. Geological Survey 

Techniques of Water-Resources Investigations, book 3, 

chap. 2, 59 p. 

Hubbard, E.F., 1992, Policy recommendations for management and retention of hydrologic data of the U.S. Geological Survey: U.S. Geological Survey Open-File 

Report 92–56, 32 p. 

Hubbard, E.F., and Barker, A.F., 1995, Selected surface-water 

technical memorandums of the U.S. Geological Survey, 

1969 to 1995: U.S. Geological Survey Open-File Report 

95–354, 497 p.

Kennedy, E.J., 1983, Computation of continuous records of 

streamflow: U.S. Geological Survey Techniques of WaterResources Investigations, book 3, chap. A13, 53 p. 

Kennedy, E.J., 1984, Discharge ratings at gaging stations: 

U.S. Geological Survey Techniques of Water-Resources 

Investigations, book 3, chap. A10, 59 p. 

Kennedy, E.J., 1990, Levels at streamflow gaging stations: 

U.S. Geological Survey Techniques of Water-Resources 

Investigations, book 3, chap. A19, 31 p. 

Kenney, T.A., 2010, Levels at gaging stations: U.S. Geological 

Survey Techniques and Methods 3-A19, 60 p.

Kilpatrick, F.A., and Schneider, V.R., 1983, Use of flumes in 

measuring discharge: U.S. Geological Survey Techniques of 

Water-Resources Investigations, book 3, chap. A14, 46 p. 

Knott, J.M., Glysson, G.D., Malo, B.A., and Schroder, L.J., 

1993, Quality assurance plan for the collection and processing of sediment data by the U.S. Geological Survey, Water 

Resources Division: U.S. Geological Survey Open-File 

Report 92–499, 18 p. 

Knott, J.M, Sholar, C.J., and Matthes, W.J., 1992, Quality 

assurance guidelines for the analysis of sediment concentration by the U.S. Geological Survey sediment laboratories: 

U.S. Geological Survey Open-File Report 92–33, 22 p. 

Matthai, H.F., 1967, Measurement of peak discharge at width 

contractions by indirect methods: U.S. Geological Survey 

Techniques of Water-Resources Investigations, book 3, 

chap. A4, 44 p. 

Moore, J.E, Aronson, D.A., Green, J.H., and Puente, Celso, 

1990, Report planning, preparation, and review guide: U.S. 

Geological Survey Open-File Report 89–275, 81 p. 
32 Surface-Water Quality-Assurance Plan for the U.S. Geological Survey Georgia Water Science Center, 2010

Mueller, D.S., and Wagner, C.R., 2009, Measuring discharge 

with acoustic Doppler current profilers from a moving boat: 

U.S. Geological Survey Techniques and Methods 3A-22, 

72 p.

 Nolan, K.M., Gray, J.R. and Glysson, G.D., 2005, Introduction to suspended-sediment sampling: U.S Geological 

Survey Scientific Investigations Report 2005–5077.

Novak, C.E., 1985, WRD data reports preparation guide, 

Water-Resources Investigations, book 3, chap. C3, 66 p. 

Porterfield, George, 1972, Computation of fluvial-sediment 

discharge: U.S. Geological Survey Techniques of WaterResources Investigations, book 3, chap. C3, 66 p. 

Rantz, S.E., and others, 1982, Measurements and computation 

of streamflow, volumes 1 and 2: U.S. Geological Survey 

Water-Supply Paper 2175, 631 p. 

Rasmussen, P.P., Gray, J.R., Glysson, G.D., and Ziegler, A.C., 

2009, Guidelines and procedures for computing time-series 

suspended-sediment concentrations and loads from instream turbidity-sensor and streamflow data: U.S. Geological Survey Techniques and Methods book 3, chap. C4, 53p.

Sauer, V.B., and Meyer, R.W., 1992, Determination of errors 

in individual discharge measurements: U.S. Geological 

Survey Open-File Report 92–144, 21 p. 

Shearman, J.O., 1990, User’s manual for WSPRO—A computer model for water surface profile computations: U.S. 

Federal Highway Administration Report, FHWA-IP-89-027, 

187 p. 

Smoot, G.F., and Novak, C.E., 1968, Calibration and maintenance of vertical-axis type current meters: U.S. Geological Survey Techniques of Water-Resources Investigations, 

book 8, chap. B2, 15 p. 

U.S. Geological Survey, 1986, Water Resources Division 

publications guide, vol. I, Publications policy and text 

preparation, 2d ed., revised by D.W. Alt and K.T. Iseri: 

U.S. Geological Survey Open-File Report 87–0205, 429 p.

U.S. Geological Survey, 2003, U.S. Geological Survey Publications Series: U.S. Geological Survey Manual 1100.3, 

accessed in November 2009 at http://www.usgs.gov/usgsmanual/1100/1100-3appendixa.pdf.

U.S. Geological Survey, 2006a, Authority to approve information products: U.S. Geological Survey Manual, 205.18, 

accessed in November 2009 at http://www.usgs.gov/usgsmanual/200/205-18.html. 

U.S. Geological Survey, 2006b, Fundamental science practices: Peer review: U.S. Geological Survey Manual 502.3, 

accessed in November 2009 at http://www.usgs.gov/usgsmanual/500/502-3.html. 

U.S. Geological Survey, 2009, Fundamental science practices: 

Review, approval, and release of information products: U.S. 

Geological Survey Manual 502.4, accessed in November 

2009 at http://www.usgs.gov/usgs-manual/500/502-4.html. 
Appendix 1. U.S. Geological Survey Technical Memorandums Cited 33

Appendix 1. U.S. Geological Survey Technical Memorandums Cited

The following technical memorandums are available online at http://water.usgs.gov/admin/memo/.

Office of Surface Water (OSW) 

OSW Technical Memorandum 2010.03

OSW Technical Memorandum 2010.01 

OSW Technical Memorandum 2009.05 

OSW Technical Memorandum 2009.01

OSW Technical Memorandum 2008.03

OSW Technical Memorandum 2008.02

OSW Technical Memorandum 2007.01

OSW Technical Memorandum 2006.05

OSW Technical Memorandum 2006.04

OSW Technical Memorandum 2006.01

OSW Technical Memorandum 2005.08

OWS Technical Memorandum 2004.04 

OSW Technical Memorandum 2004.01 

OSW Technical Memorandum 2001.03

OSW Technical Memorandum 99.06

OSW Technical Memorandum 97.01

OSW Technical Memorandum 96.04

OSW Technical Memorandum 93.07

OSW Technical Memorandum 93.01 

OSW Technical Memorandum 92.11

OSW Technical Memorandum 92.10

OSW Technical Memorandum 92.09

OSW Technical Memorandum 92.08

OSW Technical Memorandum 92.04

OSW Technical Memorandum 91.15 

OSW Technical Memorandum 91.09

OSW Technical Memorandum 90.10

OSW Technical Memorandum 90.08 

OSW Technical Memorandum 90.01

OSW Technical Memorandum 89.07

OSW Technical Memorandum 88.18

OSW Technical Memorandum 88.17

OSW Technical Memorandum 88.07

OSW Technical Memorandum 87.05

OSW Technical Memorandum 85.17

OSW Technical Memorandum 85.14

OSW Technical Memorandum 84.05

Water Resources Discipline (WRD)

WRD Technical Memorandum 2009.02

WRD Technical Memorandum 99.34

WRD Technical Memorandum 95.19

WRD Technical Memorandum 92.59

WRD Technical Memorandum 77.83

WRD Technical Memorandum 77.60

WRD Technical Memorandum 71.73

Memorandum from the Chief, 

Branch of Operational Support, May 7, 1993

Office of Water Quality (OWQ) 

OWQ Technical Memorandum 80.17

OWQ Technical Memorandum 80.07

OWQ Technical Memorandum 79.17

OWQ Technical Memorandum 77.07

OWQ Technical Memorandum 76.17

OWQ Technical Memorandum 76.04
34 Surface-Water Quality-Assurance Plan for the U.S. Geological Survey Georgia Water Science Center, 2010

Appendix 2. Hydrologic Monitoring and Analysis Section—

Surface-Water Electronic Archiving

This addendum to the GaWSC Surface-Water Quality-Assurance Plan documents the archiving of 

electronic files related to surface-water activities of the Hydrologic Monitoring and Analysis Section. All 

electronic files will be archived, grouped by streamflow-gaging station. The archival structure is documented below.

Archive Directory Structure for Station 

Description, Station Manuscripts, Station 

Analysis, and Station Photo Files

The station descriptions, station manuscripts, station 

analysis, and station photos are stored electronically on the 

GaWSC computer network.

The directory structure for Station Description Files is:

\groups\sw\Station_Descriptions\YYYY\

Where:

YYYY is the water year.

EXAMPLE: \groups\sw\Station_Descriptions\2008\

Each of the Station Description Files has the following 

naming convention:

YYYY.sd.station#.pdf

Where:

YYYY is the water year of the station description.

station# is the unique 8-digit downstream order number

for each individual gaging station.

EXAMPLE: The station description for 02335000 

Chattahoochee River near Norcross for the 2008 water 

year will have the file name 2008.sd.02335000.pdf.

The directory structure for Station Manuscript Files is:

\groups\sw\Station_Manuscript\YYYY\

Where:

YYYY is the water year.

EXAMPLE: \groups\sw\Station_Manuscripts\2008\

Each of the Station Manuscript Files has the following 

naming convention:

YYYY.sm.station#.pdf

Where:

YYYY is the water year of the station description.

station# is the unique 8-digit downstream order number 

for each individual gaging station.

EXAMPLE: The station manuscript for 02335000 

Chattahoochee River near Norcross for the 2008 water 

year will have the file name 2008.sm.02335000.pdf.

The directory structure for Station Analysis Files is:

\groups\sw\Station_Analyses\YYYY\

Where:

YYYY is the water year.

EXAMPLE: \groups\sw\Station_Analyses\2008\

Each of the Station Analysis Files has the following 

naming convention:

YYYY.sa.station#.pdf

Where:

YYYY is the water year of the station description.

station# is the unique 8-digit downstream order number 

for each individual gaging station.

EXAMPLE: The station analysis for 02335000 

Chattahoochee River near Norcross for the 2008 water 

year will have the file name 2008.sa.02335000.pdf.
Appendix 2. Hydrologic Monitoring and Analysis Section—Surface-Water Electronic Archiving 35

The directory structure for Station Photos Files is:

\groups\sw\Station_Photos\station#\

Where:

station# is the unique 8-digit downstream order number 

for each individual gaging station.

EXAMPLE: \groups\sw\Station_Photos\02335000\

Each of the Station Photos Files has the following 

naming convention:

station#_xx.jpg

Where:

station# is the unique 8-digit downstream order number 

for each individual gaging station.

## is the photo number.

EXAMPLE: The station photo for 02335000 

Chattahoochee River near Norcross will have the 

filename 02335000_01.jpg.

Archive Directory Structure for Electronic Data 

Logger (EDL) Data Files

EDL Data Files are stored on the GaWSC computer network, 

and the directory structure for EDL Data Files is:

/groups/sw/edldata/station#/datalogger/WY2XXX/

Where:

station# is the unique 8-digit downstream order number 

for each individual gaging station.

datalogger is type of datalogger that generated the data file.

WY2XXX is the water year.

EXAMPLE: /groups/sw/edldata/02335450/H510/WY2004/

Each of the EDL Data Files have the following 

naming convention:

YYMMDD_station#_datalogger.txt

Where:

YYMMDD is the year, month, and day the edl data file 

was downloaded.

station# is the unique 8-digit downstream order number 

for each individual gaging station.

datalogger is the type of datalogger that generated the 

data file.

EXAMPLE: A edl data file that was downloaded from

the 555 at Chattahoochee River above Roswell, GA 

(02335450) on May 19, 2004, will have the filename 

040519_02335450_555.txt and will be placed in the

/groups/sw/edldata/02335450/555/WY2004/ folder on 

the GaWSC computer network.

Archive Directory Structure for ADCP Files

ADCP Measurement Files are stored on the GaWSC computer 

network, and the directory structure for ADCP Measurement 

Files is:

/groups/sw/ADCP/station#/measurement#/

Where:

station# is the unique 8-digit downstream order number 

for each individual gaging station.

measurement# is the measurement number of the 

discharge measurement.

All the files (.mmt, .pd0, LBT.pd0, SBT.pd0, ASC.txt, 

LBT_ASC.txt, SBT_ASC.txt) associated with the ADCP 

measurement will be placed in the measurement folder. 

The .mmt, .pd0, LBT.pd0, SBT.pd0, ASC.txt, 

LBT_ASC.txt, and SBT_ASC.txt have the 

following format:

station#_measurement#.mmt

station#_measurement#_transect#.pd0

station#_measurement#_transect#_LBT.pd0

station#_measurement#_transect#_SBT.pd0

station#_measurement#_transect#_ASC.txt

station#_measurement#_transect#_LBT_ASC.txt

station#_measurement#_transect#_SBT_ASC.txt

Where:

station# is the unique 8-digit downstream order number 

for each individual gaging station.

measurement# is the measurement number of the 

discharge measurement.

transect# is the transect number.

LBT is loop bed test.

SBT is stationary bed test.

ASC is ascii output.
36 Surface-Water Quality-Assurance Plan for the U.S. Geological Survey Georgia Water Science Center, 2010

The .mmt file includes the moving bed test, RGTest, 

Q measurement summary, and CompCal information. 

All files should be locked before being archived. The 

output from the LC.exe program is also stored with the 

ADCP measurement.

Each of the LC.exe Output Files have the following 

naming convention:

station#_ measurement#.lcf

Where:

station# is the unique 8-digit downstream order number 

for each individual gaging station.

measurement# is the measurement number of the 

discharge measurement.

EXAMPLE: A four transect discharge measurement, 

# 55, with one loop test made at Chattahoochee River

near Norcross, GA has the files 02335000_55.mmt,

02335000_55_000.pd0, 02335000_55_001.pd0,

02335000_55_002.pd0, 02335000_55_003.pd0, 

02335000_55_000_ASC.txt, 02335000_55_001_ASC.txt,

02335000_55_002_ASC.txt, 02335000_55_003_ASC.txt,

02335000_55_000_LBT.pd0, 02335000_55_000_LBT_

ASC.txt, and 02335000_55.lcf. All twelve files are 

placed in the /groups/sw/ADCP/02335000/55/ folder.

Archive Directory Structure for ADV Files

ADV Files are stored on the GaWSC computer network, and 

the directory structure for ADV Files is:

/groups/sw/ADV/station#/measurement#/

Where:

station# is the unique 8-digit downstream order number 

for each individual gaging station.

measurement# is the measurement number of the 

discharge measurement.

All five files (.wad,.ctl,.dat.,.dis,.sum) will be placed in the 

measurement folder.

The .wad,.ctl,.dat,.dis, and .sum files have the

following format:

station#.measurement#.wad

station#.measurement#.ctl

station#.measurement#.dat

station#.measurement#.dis

station#.measurement#.sum

Where:

station# is the unique 8-digit downstream order number 

for each individual gaging station.

measurement# is the measurement number of the 

discharge measurement.

EXAMPLE: A discharge measurement, # 65, made at 

Crooked Creek near Norcross, GA has the files 

02335350.065.wad, 02335350.065.ctl, 02335350.065.dat,

02335350.065.dis, and 02335350.065.sum. All five files 

are placed in the /groups/sw/ADV/02335350/65/ folder.

Beamcheck Files are stored on the GaWSC computer network, 

and the directory structure for Beamcheck Files is:

/groups/sw/ADV/Beamchecks/serial#/

Where:

serial# is the serial number of the ADV.

The output file from the beamcheck is saved in the 

following format:

serial#.YYMMDDHHMM.bmc

Where:

serial# is the serial number of the ADCP.

YYMMDDHHMM is the year, month, day, hour, and 

minute the beamcheck was run.

EXAMPLE: A beamcheck that was run on May 19, 2004,

 at 09:12 using the ADV with a serial number of P589 has

 the file name P589.0405190912.bmc. This file is placed 

in the /groups/sw/ADV/Beamchecks/P589/ folder.

Archive Directory Structure for Index 

Velocity Files

Index Velocity Configuration Files are stored on the GaWSC 

computer network, and the directory structure for Index 

Velocity Configuration Files is:

/groups/sw/Index_Velocity_Sites/station#/Config_file/

Where:

station# is the unique 8-digit downstream order number 

for each individual gaging station.

EXAMPLE: The configuration of the index velocity meter

 at Chattahoochee River at US 27, at Franklin, GA was 

saved to a file on May 19, 2004. The configuration file, 

040519_02338500_CONFIG.txt, is placed in the /groups/

sw/Index_Velocity_Sites/02338500/Config_file/ folder.
Appendix 2. Hydrologic Monitoring and Analysis Section—Surface-Water Electronic Archiving 37

The Configuration File for an Index Velocity is saved in the 

following format:

YYMMDD_station#_CONFIG.txt

Where:

YYMMDD is the year, month, and day the configuration

file was saved.

station# is the unique 8-digit downstream order number 

for each individual gaging station.

EXAMPLE: A configuration file that was saved on 

May 19, 2004 at Chattahoochee River at US 27, at Franklin

has the file name 040519_02338500_CONFIG.txt

Index Velocity Beam Check Files are stored on the GaWSC 

computer network, and the directory structure for Index 

Velocity Beam Check Files is:

/groups/sw/Index_Velocity_Sites/station#/Beam_Check_file/

Where:

station# is the unique 8-digit downstream order number

for each individual gaging station.

EXAMPLE: A beam check was saved to a file for the

 index velocity meter at Chattahoochee River at US 27, 

at Franklin, GA on May 19, 2004. The beam check file,

040519_02338500.bmc, is placed in the /groups/sw/Index_

Velocity_Sites/02338500/Beam_Check_file/ folder.

The Beam Check File for an Index Velocity is saved in the 

following format:

YYMMDD_station#.bmc

Where:

YYMMDD is the year, month, and day the configuration

file was saved.

station# is the unique 8-digit downstream order number 

for each individual gaging station.

EXAMPLE: A beam check file that was saved on 

May 19, 2004, at Chattahoochee River at US 27, at 

Franklin has the file name 051904_02338500.bmc.

Index Velocity Data Files are stored on the GaWSC computer

network, and the directory structure for Index Velocity Data 

Files is:

/groups/sw/Index_Velocity_Sites/station#/Data_file/

Where:

station# is the unique 8-digit downstream order number 

for each individual gaging station.

EXAMPLE: The data from the index velocity meter at 

Chattahoochee River at US 27, at Franklin, GA was

 saved to a file on May 19, 2004. The data file, 

040519_02338500.arg, is placed in the /groups/sw/

Index_Velocity_Sites/02338500/Data_file/ folder.

The Data File for an Index Velocity is saved in the

following format:

YYMMDD_station#.arg

Where:

YYMMDD is year, month, and day the configuration 

file was saved.

station# is the unique 8-digit downstream order number 

for each individual gaging station.

EXAMPLE: A data file that was saved on May 19, 2004,

 at Chattahoochee River at US 27, at Franklin has the 

file name 040519_02338500.arg.

Responsibilities

It is the responsibility of the individual who generates an 

electronic file to archive the file in a timely manner. Persons 

who generate edl, measurement, or other applicable files in 

the field should archive the files according to this addendum 

within 5 working days of returning to the office. Occasionally, 

files are created in the office prior to implementation in the 

field—such files should be archived within 5 working days 

of their creation.
38 Surface-Water Quality-Assurance Plan for the U.S. Geological Survey Georgia Water Science Center, 2010

Appendix 3. Hydroacoustic Instrumentation—Standards, Policies, 

and Procedures

• OSW Technical Memorandum 2009.02, Release of 

WinRiver II Software (version 2.04) for Computing 

Streamflow from Acoustic Doppler Current Profiler

• OSW Technical Memorandum 2009.05, Publication 

of the Techniques and Methods Report Book 3, 

Section A22, “Measuring Discharge with Acoustic 

Doppler Current Profilers from a Moving Bed 

• USGS Techniques and Methods Book 3, Section A22, 

Measuring Discharge with Acoustic Doppler Current 

Profilers from a Moving Bed

ADCP Quality-Assurance Folder

An ADCP Quality-Assurance Folder is maintained by the 

designated GaWSC Hydroacoustic Specialist. The folder is 

placed in the Hydrologic Monitoring and Analysis Section and 

contains the following:

1. A list of ADCPs and serial numbers

2. ADCP maintenance logs

3. Current firmware and software for each ADCP

4. A list of trained operators in the GaWSC

5. Quality-assurance logs

6. Archival procedures and examples

7. A processing and reviewing guide

Field Procedures

1. Prior to going into the field, the operators ensure that: the 

ADCP is in working order with the latest approved firmware; their laptop contains the latest approved software; 

they have sufficient space on the PCMCIA memory card 

or CD–R; and they have a working laser range finder for 

measuring edge distances.

2. Each day the ADCP is used, a diagnostic test is performed 

and the results are recorded. The filename of the diagnostic test is included on notes of any measurement made 

with the ADCP that day.

This addendum to the GaWSC Surface Water QualityAssurance Plan presents standards, policies, and procedures 

used by the GaWSC specifically related to hydroacoustic 

instrumentation. Many standards, policies, and procedures 

documented in the main body of the Surface-Water QualityAssurance Plan apply to the use of hydroacoustics. These 

include, for example, maintenance of gaging-station infrastructure, site documentation, and general records-working 

procedures. This addendum documents standards that are 

unique to the hydroacoustic instruments used by the GaWSC. 

It is expected that this addendum will be updated as the use 

of hydroacoustics increases and as new instruments, software, 

and firmware are introduced. This addendum is subdivided by 

instrument category:

1. Acoustic Doppler current profiler (ADCP or ADP)

2. Acoustic Doppler Velocimeter (ADV)

3. Index-velocity meter

Acoustic Doppler Current Profiler

Acoustic Doppler current profilers are used by the 

GaWSC to make medium- and high-water discharge measurements. All ADCP operators read and become familiar with the 

information contained in the following policy memorandums 

and reports:

• OWS Technical Memorandum 2006.04, Availability 

of the report “Application of the Loop Method for 

Correcting Acoustic Doppler Current Profiler 

Discharge Measurements Biased by Sediment Transport” by David S. Mueller and Chad R. Wagner 

(Scientific Investigations Report 2006–5079) and 

guidance on the application of the Loop Method

• USGS Scientific Investigations Report 2006–5079, 

Application of the Loop Method for Correcting 

Acoustic Doppler Current Profiler Discharge 

Measurements Biased by Sediment Transport

• OSW Technical Memorandum 2008.02, Upgrade for 

Rio Grande/Workhorse Firmware to Address Potential 

Bias in Discharges Measured Using Water Mode 12

• OSW Technical Memorandum 2008.03, Hydroacoustics

Work Group—Charter, Membership, and Activities
Appendix 3. Hydroacoustic Instrumentation—Standards, Policies, and Procedures 39

3. Prior to each measurement, a moving-bottom check is 

performed by using the loop method documented in 

Mueller and Wagner (2005). The moving-bottom check is 

recorded and archived with the rest of the measurementdata files. The LC.exe program must be used to compute 

the moving bed adjustment for the loop method test. 

The program, installation files, and installation instructions can be found at http://hydroacoustics.usgs.gov/. If 

conditions at the site do not allow for the use of the loop 

method, then multiple (at least three) stationary moving 

bed tests need to be performed throughout the measuring 

section. Each stationary moving bed test should be at least 

5 minutes if the boat is held stationary by either tether or 

anchor. However, if the ADCP cannot be held precisely, a 

moving-bottom check of 10 minutes is needed to differentiate actual boat movement from apparent upstream movement caused by a moving-bottom condition.

4. The water temperature near the ADCP needs to be 

measured with an independent field thermometer before 

every measurement to ensure that the thermistor in the 

ADCP is working properly. If the independent thermometer reading differs from the ADCP water temperature 

reading by more than 1 degree Fahrenheit, then the 

ADCP must be sent back to the manufacturer to correct 

the problem with the thermistor. 

5. The estimates used for edge distances shall always be 

measured. Distance may be measured, using a laser range 

finder, tag line, or rule.

6. When using an RD Instruments Rio Grande with 

WinRiver software, operators use the Configuration 

Wizard to set up the measurement. If any settings other 

than the Configuration Wizard settings are used, the reasons for the user settings are explained on the 

measurement note sheet.

7. The depth to the transducer below water surface shall 

always be verified before each measurement.

8. In accordance with OSW requirements, if all of the first 

four transects are not within 5 percent of the mean, at 

least four additional transects shall be made. Note: 

There are exceptions for unsteady flow.

9. After each measurement, or at least once a day, all measurement data and diagnostic tests are backed up temporarily on a removable medium such as a PCMCIA flash 

card (recommended), CD–R, or USB memory stick.

Office Post-Field Procedures

ADCP measurements are processed, archived, and 

reviewed within 5 working days after returning from the field. 

Data are archived in accordance with the Hydrologic Monitoring and Analysis Section Archiving Addendum. An example 

of data archival for ADCP measurements can be found in the 

ADCP Quality-Assurance Folder.

The ADCP operator is responsible for archiving all ADCP 

measurement and diagnostic files, processing all measurements, entering the measurement data into the database, and 

finding a trained ADCP operator to review each measurement.

The reviewer of an ADCP measurement is responsible 

for ensuring that correct methods were used to collect and 

process the measurements, measurement notes are accurate, 

measurement data have been archived correctly, and that the 

measurement notes have been filed. If any changes are made 

during the review process, the changes should be discussed 

with the original ADCP operator, the database updated, and 

measurement notes filed.

Acoustic Doppler Velocimeter

Acoustic Doppler velocimeters (ADVs), designed for 

use with a standard USGS top-setting wading rod, are used 

by the GaWSC to make wading discharge measurements. The 

make and model ADV used for this application is the SonTek®

Flowtracker. All Flowtracker operators read and become 

familiar with the information contained in the following 

policy memorandum:

• OSW Technical Memorandum 2004.04, Policy on the 

Use of the Flowtracker for Discharge Measurements

• OSW Technical Memorandum 2007.01, SonTek/YSI 

FlowTracker firmware version 3.10 and software 

version 2.11 upgrades and additional policy on the use 

of FlowTrackers for discharge measurements

• OSW Technical Memorandum 2009.04, Application 

of FlowTracker firmware and software mounting 

correction factor for potential bias

Field Measurements

1. Prior to use of the Flowtracker, the users familiarize themselves thoroughly with the instrument by reading the Flowtracker Handheld ADV Technical Documentation, including 

the Introductory Documentation, Operation Manual, and 

Principles of Operation. Users also familiarize themselves 

with the Flowtracker handheld controller, including all 

keypad operations, prior to collecting field data.
40 Surface-Water Quality-Assurance Plan for the U.S. Geological Survey Georgia Water Science Center, 2010

2. Prior to and after a field trip, the users perform a full 

diagnostic test on the ADV, called a beamcheck, using the 

manufacturer’s Flowtracker Software. The test procedures 

are described in the Flowtracker Operations Manual. The 

software displays signal-strength plots for each ADV 

receiving transducer. The Flowtracker Operations Manual 

describes the beamcheck and provides examples of good 

and problem signal-strength plots. If signal-strength plots 

indicate a possible malfunction, the Flowtracker is not 

used to collect field data. In all instances every diagnostic 

test is logged to a file, and the filename is noted on the 

measurement note sheet. All diagnostic files are archived 

electronically. In the event of an instrument malfunction, diagnostic files can be provided to the manufacturer 

for troubleshooting. If a malfunction is suspected or if 

there has been a shock to the probe (such as striking a 

hard object), a beamcheck is performed prior to further 

collection of field data.

3. Prior to each discharge measurement or velocitycollection run, the user checks the ADV, using the handheld controller Systems Functions Menu. The following 

items are checked:

• System clock. The clock displays the correct date/time.

• Recorder status. There is adequate data-storage capacity for the discharge measurement or velocity data run.

• Temperature data. The ADV probe is immersed in 

the stream and the temperature noted. At least once 

daily, the temperature recorded by the ADV is checked 

against a temperature reading from an independent 

source, such as a digital thermometer. It is very important for velocity and discharge accuracy for the ADV 

to record water temperature accurately. A 5-degree 

(Celsius) error in temperature would result in a 2-

percent error in the velocity and discharge measurement. The user ensures that the temperature has stabilized prior to start of data collection. The temperature 

is noted on the discharge measurement note sheet. If 

the independent thermometer reading differs from the 

ADV water temperature reading by more than 1 degree 

Fahrenheit, then ADV must be sent back to the manufacturer to correct the problem with the thermistor. 

• Battery data. Battery voltage is checked to ensure 

adequate capacity for the discharge measurement or 

velocity data run.

• Signal-to-noise ratios. The Flowtracker technical 

memorandum recommends that SNRs be greater than 

10. Analysis of field data indicates that SNRs can be 

as low as 4 and adequate data still can be collected. 

However, data collected with SNRs below 10 are 

scrutinized carefully, using other quality-assurance 

parameters described in the Measurement QualityAssurance section of this memorandum. If low SNRs 

appear to be causing data-quality problems, a different 

measurement section might be investigated. Backscatter can change with measurement location.

4. If the Flowtracker is being used in water other than freshwater, the salinity at the data-collection location is measured with an approved sensor, and the measured salinity 

is entered in the handheld controller Setup Parameters 

Menu. A 12 parts-per-thousand error in salinity can result 

in a 2-percent error in velocity and discharge measurement.

5. The Flowtracker is designed for mounting on a standard 

top-setting wading rod. It is recommended that an offset 

bracket available from the Flowtracker manufacturer be 

used to mount the Flowtracker probe head to the wading 

rod. Without the bracket, the Flowtracker sample volume 

is located about 4 inches from the wading rod. With the 

bracket, the sample volume is located about 2 inches from 

the wading rod, closer to the point of depth measurement. 

The bracket was designed to move the sample volume as 

close to the wading rod as possible while remaining outside the flow disturbance caused by the wading rod.

6. When mounting the Flowtracker, special care is taken to 

protect the cable from abrasion. The cable is very prone to 

environmental noise that can degrade measurement quality.

7. The Flowtracker probe head should be oriented so that the 

longitudinal axis passing through the center transmitting 

transducer is parallel to the tagline, and the receiving arm 

with the red band should be downstream. Effort is made 

to hold the wading rod level so that the sample volume 

does not strike a boundary. Pay close attention to the flow 

angle reported by the Flowtracker.

8. To avoid striking a boundary, the user should have a sense 

of where the sample volume is located. The sample volume 

should be more than 2 inches from any boundaries. If a 

boundary cannot be avoided and a point velocity measurement has to be made less than 2 inches from a boundary, 

then the point velocity measurement should be scrutinized 

carefully and quality-assurance parameters should be used 

to assess the quality of the measured velocity.

9. All policies and recommendations for making wading 

discharge measurements with Price-type current meters 

are followed when using Flowtrackers, with the exception 

of the minimum recommended velocity thresholds and the 

application of alternative means of measuring velocities in 

the vertical (Rantz, 1982, p. 132).

10. The minimum recommended velocity threshold for the 

Flowtracker is 0.1 ft/s; the instrument velocity error at 

0.1 ft/s is about 4 percent. If measured velocities are less 

than 0.1 ft/s, the measurement should not be rated better 

than “fair.”
Appendix 3. Hydroacoustic Instrumentation—Standards, Policies, and Procedures 41

11. The one-point (0.6 times depths) vertical-velocity method 

is used for depths equal to or less than 1.5 feet. For depths 

greater than 2.5 feet, the two-point (0.2 and 0.8 times 

depth) method is used. If the depths are between 1.5 and 

2.5 feet, then either the one-point or two-point method is 

used. The method to use in this range depends if velocity 

follows a standard profile. If, when using the two-point 

method, the 0.2 measured velocity is less than the 

0.8 velocity, or if the 0.8 velocity is less than half of the 

0.2 velocity, the handheld controller screen informs the 

user, and the user then has the option to measure the 

velocity at the 0.6 position (three-point method). The 

user, in this situation, should measure velocity at the 

0.6 position.

12. Special care is taken with the Flowtracker to protect the 

probe head. If the probe receiver arms are bent or the 

transducers scratched, the unit is no longer usable and 

needs to be repaired by the manufacturer. The unit always 

should be transported by securing it in the manufacturer’s 

carrying case to prevent damage. Other maintenance considerations included Operator’s Manual also are followed.

13. It is recommended that measurement files recorded on the 

handheld controller be downloaded at least once a day for 

backup purposes.

14. Standard USGS measurement notes may be used to 

document the discharge measurement.

15. If a discharge measurement made with a Flowtracker 

warrants a check measurement, then the check measurement should be made with a conventional meter, such as 

the Price AA or pygmy current meter.

Measurement Documentation

For each measurement run of discharge or velocity, a 

file with a .WAD extension is generated and stored on the 

handheld controller. The .WAD file is downloaded from the 

controller, then the Flowtracker software is used to extract 

four files from the .WAD file:

1. .CTL file — an ASCII file containing the Flowtracker 

configuration.

2. .DAT file — an ASCII file containing 1-second velocity

component and signal-to-noise ratios.

3. .SUM file — an ASCII file containing station information 

and summary statistics from each measurement.

4. .DIS file — an ASCII file containing a dischargemeasurement summary.

A paper copy of the .DIS file is printed and attached 

to the measurement note sheet for filing. All four extracted 

electronic files plus the .WAD file are archived permanently as 

specified in the Hydrologic Monitoring and Analysis Section 

Surface-Water Electronic Archiving appendix. The .WAD file 

contains important data that are not extracted with any of the 

four files and could be valuable for instrument diagnostics in 

the event of malfunctions.

Measurement Quality Assurance

The following is a list of recommendations for using 

Flowtracker parameters to help assess the quality of discharge 

measurements. These parameters are not available with Pricetype meters. Guidelines for using the parameters are:

• Velocity standard error. If the average standard error 

for the measurement exceeds 8 percent of the mean 

measurement velocity, the measurement should be 

rated no better than “fair.” If the standard error exceeds 

10 percent of the mean measurement velocity, the 

measurement should be rated no better than “poor.”

• Boundary flag. There are four possible boundary flags 

assigned to each station: “best,” “good,” “fair,” and 

“poor.” A boundary flag of “best” does not guarantee 

a lack of boundary interference (see the Flowtracker 

Technical Documentation). If the ADV sample volume 

was striking a solid boundary, a “best” flag likely still 

would be displayed, but the measured velocity could 

be biased toward zero.

• Velocity spikes. An excessive number of velocity spikes 

(more than 10 spikes per measurement) could be cause 

to downgrade the measurement.

• Flow angles. A good measurement section typically 

shows some flow-angle variations, but with angles 

less than 20 degrees.

Periodic Quality-Assurance Checks

Each Flowtracker must be checked for dischargemeasurement accuracy at least annually and also after any 

hardware or firmware changes. The check consists of making 

a discharge measurement at a site where the Flowtrackermeasured discharge can be compared with a known discharge 

derived from some other source. Appropriate sources of 

comparison discharge would be discharge obtained from a 

stable discharge rating, or discharge measured with a second 

Flowtracker or mechanical meter known to meet USGS 

calibration standards.
42 Surface-Water Quality-Assurance Plan for the U.S. Geological Survey Georgia Water Science Center, 2010

Index-Velocity Meter

The GaWSC uses acoustic Doppler velocity meters 

(ADVMs) installed at gaging stations to index mean channel 

velocities for the computation of records of discharge.

Personnel who use index-velocity instruments for the 

production of discharge records obtain training by attending 

the Office of Surface Water class “Streamflow Records 

Computation using Hydroacoustic Current Meters and IndexVelocity Methods” that is offered periodically.

Installation

1. A thorough site reconnaissance is required prior to 

installation of an index-velocity meter at an existing 

gaging station or establishment of a new index-velocitymeter station. The site reconnaissance includes channel 

surveys and the collection of velocity and temperature 

profiles. The channel bed is characterized for stability. 

The site hydraulics are analyzed carefully for factors that 

potentially could cause rating instabilities. Other considerations include protection of the instrument, power/

communications cable-length limitations, and adequate 

power supply. The data collected from the reconnaissance 

are used to ascertain the success of using an indexvelocity meter. For ADVMs, aspect ratios (range/depth) 

and bridge-pier wake-turbulence zone can be computed 

to see if the ADVM sample volume will reach a zone of 

stable velocities.

2. Gage-site-selection criteria documented in Rantz and others 

(1982, p. 5–9) remain applicable for index-velocity sites.

3. The index-velocity-meter deployment program is 

recorded and archived. If the index-velocity-meter 

deployment program can be saved, the deployment program is archived. Some index-velocity-meter programs 

cannot be saved directly. In these instances, a screen 

capture of the instrument deployment can be used to save 

the program parameters. A paper copy of the pertinent 

parameters is placed in the gage-house folder.

Field Procedures

The following procedures are followed during visits to 

stations equipped with index-velocity meters:

1. A temperature reading from an independent source, such 

as a digital thermometer, is taken near the instrument. 

The temperature is recorded in the field notes along with 

the time of the reading. If the independent thermometer 

reading differs from the ADVM water temperature 

reading by more than 1 degree Fahrenheit, then ADVM 

must be sent back to the manufacturer to correct the 

problem with the thermistor. 

2. For ADVMs, a beam-amplitude diagnostic test is run 

and logged in a file. All such files are archived according to the Hydrologic Data Section Surface-Water 

Electronic Archiving appendix. Beam-amplitude checks 

are an invaluable diagnostic and quality-assurance tool. 

The beam-amplitude checks must show that the ADVM 

sample cell is free of obstructions and is sized so that 

beam amplitudes at the end of the sample cell are a 

minimum of 5 counts above the instrument noise level. 

If these criteria are not met, the ADVM sample cell must 

be adjusted until the requirements are met. All samplecell changes must be noted on the station log and in field 

notes and the new instrument deployment saved. If the 

sample-cell size changes significantly, a new indexvelocity rating likely is needed.

3. If the gage does not have data telemetry or if all logged 

parameters are not transmitted, the datalogger data are 

downloaded for each site visit and the data are input to 

NWIS at the office.

4. At least once annually, the standard cross section is 

checked to ensure that the channel geometry has not 

changed significantly. For channels with known scour 

or fill potential or for channels with the potential for 

dredging, the standard cross section may need to be 

checked more frequently. If possible, discharge measurements can be made at the standard cross-section location. 

The advantage of this approach is that for every measurement, the standard cross section is checked.
Appendix 3. Hydroacoustic Instrumentation—Standards, Policies, and Procedures 43

5. The frequency of discharge measurements is dictated by 

stability of the stage-area and index-velocity ratings and 

by the range of measurements used to define the ratings. 

Changes in index-velocity instrumentation or changes to 

existing instrument program parameters (for example, 

ADVM sample-cell-size changes) likely necessitate the 

need for a new index-velocity rating and, hence, morefrequent measurements to establish the new rating. It may 

be possible to reduce measurement frequency once stable 

ratings have been established for a wide range of flows. 

All sites, however, must be measured at least two times 

a year.

Data Quality Assurance

All data quality parameters available are used to assess 

the quality of the velocity (and stage) record used to generate 

discharge records. For ADVMs, these parameters can include 

cell end, velocity standard deviation, velocity y-component, 

water temperature, and signal strength (average backscatter 

amplitude). Unit-value plots are valuable for examining these 

quality-assurance parameters.

Discharge Computation

The same general USGS policies and recommendations 

that apply to stage-discharge methods used to produce 

discharge records apply to index-velocity methods. Thus, 

guidelines for the production of streamflow records presented 

in the section entitled Processing and Analysis of Streamflow 

Data outlined in the GaWSC Surface-Water QualityAssurance Plan apply to index-velocity methods. Polices and 

recommendations regarding stage data, such as the editing or 

deleting of unit values, apply to velocity unit values as well. 

Likewise, guidelines for records documentation—including 

the station analysis, daily values tables, and other supporting 

materials—are applicable to index-velocity records.
Manuscript approved for publication, October 20, 2010

Edited by Rebecca J. Deckard

Layout by Caryl J. Wipperfurth

For more information concerning the research in this report, contact

USGS Georgia Water Science Center

3039 Amwiler Road

Atlanta, Georgia 30360

telephone: 770-903-9100

http://ga.water.usgs.gov
Gotvald, A.J.—Surface-Water Quality-Assurance Plan for the U.S. Geological Survey Georgia Water Science Center, 2010—Open-File Report 2010–1263