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Supersedes Water-Resources Investigations Report 00-4252

Guidelines and Standard Procedures for Continuous Water-Quality Monitors: Station Operation, Record Computation, and Data Reporting

By Richard J. Wagner, Robert W. Boulger, Jr., Carolyn J. Oblinger, and Brett A. Smith


This report provides basic guidelines and procedures for use by U.S. Geological Survey (USGS) personnel in site and water-quality monitor selection, field procedures, calibration of continuous water-quality monitors, record computation and review, and data reporting. Two techniques for servicing continuous monitors are discussed in this report: (1) a method for servicing monitors in a well-mixed, stable, or slowly changing aquatic environment; and (2) a method for servicing monitors in a dynamic, rapidly changing aquatic environment as is commonly found in estuaries. A discussion of alternative methods for servicing monitors also is included. These basic guidelines are minimal requirements that may need to be modified to meet local environmental conditions. Knowledge of the operation of the monitoring equipment and first-hand knowledge of the watershed form the core of the data evaluation process. Record-computation procedures presented in this report provide a uniform set of minimum requirements for computing records. Examples of the application of scientific judgment in the evaluation of data records are discussed and are, by necessity, site specific. Other specific examples also are included to demonstrate the range of environmental conditions that affect the evaluation process.

Version 1.0

Posted April 2006

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Table of Contents



Purpose and Scope


Water-Quality Monitoring Station Operation

Site Selection

Monitor Selection

Monitor Configurations and Sensors

Types of Sensors


Specific Conductance


Dissolved Oxygen

Percentage of Dissolved Oxygen Saturation



Instrument Acceptance Criteria

Placement of Sensors in the Aquatic Environment

Stream Cross-Section Surveys

Lake or Estuary Vertical Profiles

Use and Calibration of Field Meters


Specific Conductance

Dissolved Oxygen



Monitor Operation and Maintenance

Standard Protocol


Sensor Inspection and Calibration Check

Steady-State Conditions

Rapidly Changing Conditions

Alternative Methods for Servicing a Monitor

Monitor Calibration Criteria

Field Cleaning of Sensors

Field Calibration of Sensors

Temperature Sensors

Specific Conductance Sensors

Dissolved Oxygen Sensors

pH Sensors

Turbidity Sensors

Troubleshooting Procedures

Requirements for Field Notes and Instrument Logs

Record Computation

Data-Processing Procedures

Initial Data Evaluation

Application of Data Corrections

Corrections for Fouling

Corrections for Calibration Drift

Other Corrections

Evaluation of Cross-Section Data Corrections

Computation of Salinity

Computation of Percentage of Dissolved Oxygen Saturation

Final Data Evaluation

Maximum Allowable Limits for Reporting Continuous Data

Publication Criteria

Preparation of the Review Package

Record Checking

Station Description

Station Analysis


Level of Review Required

Contents of the Review Package

Data Reporting

Data Reports

Data-Qualification Statements

Reporting Parameter Codes and Units

Archiving of Records




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