Cover photograph: Spring Brook Creek at Orillia, Washington, taken by David K. Mullis.
U.S. GEOLOGICAL SURVEY

Water-Resources Investigations Report 00–4252

Guidelines and Standard Procedures for Continuous 

Water-Quality Monitors: Site Selection, Field 

Operation, Calibration, Record Computation, 

and Reporting

By Richard J. Wagner, Harold C. Mattraw, George F. Ritz, and Brett A. Smith

Reston, Virginia

2000
U.S. DEPARTMENT OF THE INTERIOR

BRUCE BABBITT, Secretary

U.S. GEOLOGICAL SURVEY

Charles G. Groat, Director

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

from:

U.S. Geological Survey

Branch of Information Services

Box 25286, Federal Center

Denver, CO 80225

The use of firm, trade, and brand names in this report is for identification purposes 

only and does not constitute endorsement by the U.S. Geological Survey.

Chief, Office of Water Quality

U.S. Geological Survey

412 National Center

Reston, VA 20192
Contents III

CONTENTS

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

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

Purpose and scope ...................................................................................................................................................... 1

Acknowledgments....................................................................................................................................................... 2

Water-quality monitoring site operation ............................................................................................................................... 2

Monitor selection ....................................................................................................................................................... 2

Types of monitor configuration .................................................................................................................................. 2

Types of sensors ............................................................................................................................................... 5

Temperature ............................................................................................................................................ 5

Specific conductance .............................................................................................................................. 6

Dissolved oxygen ................................................................................................................................... 6

pH ........................................................................................................................................................... 6

Turbidity ................................................................................................................................................. 7

Instrument acceptance criteria .......................................................................................................................... 7

Site selection .............................................................................................................................................................. 7

Placement of sensors in the cross section .................................................................................................................. 9

Field meter calibration ............................................................................................................................................... 10

Temperature ...................................................................................................................................................... 10

Specific conductance ........................................................................................................................................ 10

Dissolved oxygen ............................................................................................................................................. 11

pH ..................................................................................................................................................................... 11

Turbidity ........................................................................................................................................................... 11

Monitor operation ....................................................................................................................................................... 11

Maintenance ..................................................................................................................................................... 12

Sensor inspection ............................................................................................................................................. 12

Monitor calibration criteria .............................................................................................................................. 13

Field cleaning of sensors .................................................................................................................................. 13

Field calibration of sensors .............................................................................................................................. 14

Temperature sensors ............................................................................................................................... 14

Specific conductance sensors ................................................................................................................. 14

Dissolved oxygen sensors ...................................................................................................................... 15

pH sensors .............................................................................................................................................. 16

Turbidity sensors .................................................................................................................................... 16

Cross-section measurements ............................................................................................................................ 17

Troubleshooting procedures ............................................................................................................................. 17

Field notes and instrument logs ........................................................................................................................ 17

Record computations ............................................................................................................................................................ 18

Data-processing procedures ....................................................................................................................................... 18

Initial data evaluation ....................................................................................................................................... 18

Application of corrections and shifts ............................................................................................................... 19

Fouling ................................................................................................................................................... 20

Drift ........................................................................................................................................................ 21

Evaluation and application of cross-section corrections .................................................................................. 22

Final data evaluation ........................................................................................................................................ 22

Maximum allowable limits for reporting continuous data ..................................................................... 22

Publication criteria ................................................................................................................................. 23

Preparation of the review package ............................................................................................................................. 24

Record checking ............................................................................................................................................... 24

Station description ............................................................................................................................................ 24

Station analysis ................................................................................................................................................. 24
IV Contents

Contents of the review package ........................................................................................................................ 25

Documentation .................................................................................................................................................. 25

Level of review required ................................................................................................................................... 25

Publication ............................................................................................................................................................................ 25

Data reports ................................................................................................................................................................. 25

Data qualification statements ...................................................................................................................................... 26

Archiving of records ............................................................................................................................................................. 26

Summary ............................................................................................................................................................................... 26

Selected references ............................................................................................................................................................... 26

Appendixes ........................................................................................................................................................................... 28

1. Example for calculation of average pH ...................................................................................................................... 29

2. Station description: (A) contents of a station description, and (B) example of a station 

description for the Columbia River at Beaver Army Terminal near Quincy, Oregon ............................................... 30

3. Station analysis: (A) contents of a station analysis, and (B) example of a station analysis

for temperature on the Columbia River at Beaver Army Terminal near Quincy, Oregon ......................................... 34

4. U.S. Geological Survey water-quality monitor field-inspection form (duplex) ........................................................ 37

5. Effects of temperature on pH standards ..................................................................................................................... 39

6. Troubleshooting problems with water-quality monitors ............................................................................................ 40

7. Example of an ADAPS primary data table ................................................................................................................ 42

8. Graphic representation of variable shift corrections................................................................................................... 44

9. Example of a manuscript station description ............................................................................................................. 45

10. Example of an annual field measurement summary form .......................................................................................... 46

11. Example of a variable shift correction table ............................................................................................................... 47

12. Example of a datum shift correction table ................................................................................................................. 48

13. Example of an ADAPS daily-values table ................................................................................................................. 49

14. Example of a discharge hydrograph .......................................................................................................................... 52

15. Example of a review graph for an individual water-quality property ......................................................................... 53

Figures

1. Flow-through water-quality monitoring station ......................................................................................................... 3

2. In-situ water-quality monitoring station .................................................................................................................... 4

3. Self-contained water-quality monitoring sensor and recording system ..................................................................... 5

4. Specific conductance at Duwamish River at Tukwila, Washington, September 5–10, 1998 .................................... 19

5. Generalized graph of corrections to continuous temperature record ......................................................................... 21

Tables

1. Principal advantages and disadvantages of flow-through monitoring systems ......................................................... 4

2. Principal advantages and disadvantages of in-situ monitoring systems .................................................................... 4

3. Principal advantages and disadvantages of the self-contained monitoring system ................................................... 5

4. Factors for consideration in the placement and installation of continuous 

water-quality monitoring systems ............................................................................................................................. 8

5. Hydraulic conditions of the ideal gage site ................................................................................................................ 9

6. Calibration criteria for continuous water-quality monitors ........................................................................................ 13

7. Criteria for water-quality data shifts .......................................................................................................................... 20

8. Maximum allowable limits for continuous water-quality monitoring sensors .......................................................... 23

9. Rating continuous water-quality records ................................................................................................................... 23
Abstract 1

Guidelines and Standard Procedures for Continuous 

Water-Quality Monitors: Site Selection, Field 

Operation, Calibration, Record Computation, 

and Reporting

By Richard J. Wagner, Harold C. Mattraw, George F. Ritz, and Brett A. Smith

ABSTRACT

The U.S. Geological Survey uses 

continuous water-quality monitors to assess 

variations in the quality of the Nation’s surface 

water. A common system configuration for data 

collection is the four-parameter water-quality 

monitoring system, which collects temperature, 

specific conductance, dissolved oxygen, and pH 

data, although systems can be configured to 

measure other properties such as turbidity or 

chlorophyll. The sensors that are used to measure 

these water properties require careful field 

observation, cleaning, and calibration procedures, 

as well as thorough procedures for the 

computation and publication of final records. 

Data from sensors can be used in 

conjunction with collected samples and chemical 

analyses to estimate chemical loads. This report 

provides guidelines for site-selection 

considerations, sensor test methods, field 

procedures, error correction, data computation, 

and review and publication processes. These 

procedures have evolved over the past three 

decades, and the process continues to evolve with 

newer technologies. 

INTRODUCTION

Water quality changes over time, necessitating 

repeated measurements to characterize variations in 

quality adequately. When the time interval between 

repeated measurements is sufficiently small, the 

resulting record of water quality can be considered 

continuous. A device that automatically measures 

water quality in this way is called a continuous waterquality monitor. These monitors have sensors and 

recording systems to measure physical and chemical 

water-quality properties at discrete time intervals at 

point locations. Operation of a water-quality 

monitoring station provides a nearly continuous record 

of water quality that can be processed and published or 

distributed directly by telemetry or on the World Wide 

Web. The water-quality record provides a nearly 

complete record of changes in water quality as well as 

a basis for computation of constituent loads at a station. 

Data from the sensors also can be used as surrogates for 

the measurement of other constituents by using 

regression analyses to provide estimates of 

instantaneous chemical loads. Emerging sensor 

technology is broadening the variety of measurable 

chemical constituents and is reducing limits of 

detection. As it has become possible to make near realtime water-quality monitoring data available on the 

World Wide Web, continual progress is being made to 

improve applications and refine quality-control 

procedures.

Purpose and Scope

This report provides basic guidelines and 

procedures for U.S. Geological Survey (USGS) site 

selection and operation of continuous water-quality 

monitors, field data evaluation, and subsequent record 
2 Guidelines and Standard Procedures for Continuous Water-Quality Monitors

computations. The basic guidelines are minimal 

requirements that may need to be modified to meet 

local environmental conditions. This report provides 

examples of the application of scientific judgment in 

the evaluation of data records. Field training with the 

monitoring equipment and first-hand knowledge of the 

watershed form the core of the data-evaluation process. 

Record-computation procedures provide a uniform set 

of minimum requirements for computing records. 

Adoption of these water-quality record procedures will 

ensure that published data are properly documented.

Representative illustrations of the application of 

scientific judgment are, by necessity, site specific. 

Other specific examples are used to demonstrate the 

range of environmental conditions that affect the 

evaluation process. The final evaluation to determine 

portions of the record that are published requires 

careful review and verification of the data, but much is 

left to the professional judgment and observations of 

the hydrographer operating the station. A set of 

considerations that represent a sound basis for the 

operation of a water-quality station, data evaluation, 

and publication criteria is presented in this report.

Acknowledgments

The authors wish to acknowledge the support, 

technical contributions, and advice of USGS 

colleagues in the preparation of this document. Gary L. 

Pederson and the Southeastern Region provided 

technical support for production of this report. Walton 

H. Low, G. Douglas Glysson, and Janice R. Ward 

reviewed and provided important critiques of several 

versions of this report. Special thanks to Trudy J. 

Bennett and Andrew C. Ziegler for contributions to 

sections of the report that address turbidity and to Ann 

Vanderpool for input on the use of draft guidelines in 

the field. Kirk P. Smith provided the provisional field 

form used in this report, and Douglas O. Cushman 

assembled the Columbia River review forms.

Internal (unpublished) continuous water-quality 

monitoring procedures documented by the Colorado, 

Maine, Michigan, North Carolina, Ohio, Oregon, 

Texas, and Washington Districts significantly 

contributed to the development of these guidelines as 

well as previously published guidelines. Special thanks 

go to Brett A. Smith who co-authored an earlier version 

of this report and provided valuable insights to the 

record computation process. The encouragement of 

Brett, Rebecca Deckard, and Gary Pederson is 

gratefully acknowledged.

WATER-QUALITY MONITORING SITE 

OPERATION

Physical and chemical measurements in streams 

can be made at discrete intervals to provide a nearly 

continuous record of stream water quality. Major 

factors in the operation of a continuous water-quality 

site include selection of sensors and types of monitors, 

the type of monitor configuration, site selection, 

location of the sensors in the stream cross section, the 

use and calibration of field meters, and the actual 

operation of the continuous water-quality monitors. 

Sensor and site selection are guided by the purpose of 

monitoring and the data objectives. The main objective 

in the placement of the sensors is the selection of a 

stable, secure location that is representative of the 

stream.

Monitor Selection

The selection of a water-quality monitor 

involves four major interrelated elements—(1) the 

purpose of the data collection, (2) the type of 

installation, (3) the type of sensor deployed at the 

installation, and (4) the specific sensors needed to 

satisfy the accuracy and precision requirements of the 

data-quality objectives. 

The most widely used water-quality sensors in 

monitoring installations are temperature, specific 

conductance, dissolved oxygen (DO), pH, and 

turbidity. Sensors also are available to measure 

oxidation-reduction potential, water level, depth, 

salinity, ammonia, nitrate, chloride, and chlorophyll; 

but the focus of this report is on temperature, specific 

conductance, DO, pH, and turbidity. The sensors 

needed to measure these properties are available as 

single instruments or in various combinations. For 

clarity in this report, a sensor is referred to as a 

particular lone sensor or a sensor that is detachable 

from a combination. A group of sensors configured 

together commonly is referred to as a sonde, which 

typically has a single recording unit or electronic data 

logger to record the output from the multiple sensors.

Types of Monitor Configuration

In general, three types of configurations are used 

for water-quality monitors. The flow-through 

monitoring system generally has a pump that delivers 

water to the sensor(s) mounted in a shelter; the second 

configuration is one in which the sensors are placed in 
Types of Monitor Configuration 3

situ (immersing a field measurement sensor directly 

into the water); and the third configuration is a selfcontained sensor and recording system that requires no 

external power and is placed in situ. Each configuration has advantages and disadvantages in relation to 

site location and data-quality objectives.

The flow-through monitoring system has a pump 

to convey water from the stream to a tank inside a 

shelter that contains the monitoring sensor or sonde 

(fig. 1). Typical pumps require 120-volt alternating 

current (AC) and deliver about 10 gallons of water per 

minute. If access to power is not a problem, then other 

site considerations become important (table 1); the 

advantages and disadvantages of the flow-through 

monitoring system must be compared to the data 

objectives.

Figure 1. Flow-through water-quality monitoring station. (PHOTOGRAPH: RAMAPO

RIVER AT POMPTON LAKES, NEW JERSEY, BY MICHAEL J. DELUCA)
4 Guidelines and Standard Procedures for Continuous Water-Quality Monitors

The sensors in the in-situ monitoring system are 

placed at the measuring point in the stream cross section 

(fig. 2). Cables run from the sensors to the recording 

equipment that is housed in a shelter. The primary 

advantage of this configuration is that no power is 

needed to pump water (table 2). Direct current, 12-volt 

batteries easily meet the power requirements of the 

sensors and recording equipment. In-situ water-quality 

monitoring systems can be installed at remote locations 

where AC power is not available, but the advantages 

and disadvantages of the in-situ monitoring system also 

must be considered.

Table 2. Principal advantages and disadvantages of in-situ 

monitoring systems.

Advantages Disadvantages

No power is needed to 

pump water.

Sensors are susceptible to vandalism.

Remote locations are 

possible.

The water flow cannot be treated to 

reduce fouling.

Smaller shelters can be 

used.

In shallow bank installations, the 

proper location of sensors in the 

cross section is difficult.

Pumping maintenance is 

not required.

Servicing sensors during flooding 

can be difficult.

Freeze protection is 

provided to the sensors.

Sensors are susceptible to debris or 

high flow.

Electrical hazards are 

reduced.

Shifting channels may cause 

movement of the equipment.

Table 1. Principal advantages and disadvantages of flowthrough monitoring systems

Advantages Disadvantages

Unit can be coupled with 

chlorinators to reduce 

membrane fouling.

120-volt AC power source is needed.

Expensive sensor systems 

can be secured in 

vandal-proof shelters.

Higher installation costs are incurred.

Calibration can be performed in the shelter. Pumps tend to clog in streams with 

algal fouling or high sediment 

loads.

Electrical shock protection is 

required.

Pumps may be damaged by corrosive 

waters.

Pump maintenance is required.

Pumping may cause changes in water 

quality.

Figure 2. In-situ water-quality monitoring station. 

(PHOTOGRAPH: SPRING BROOK CREEK AT ORILLIA, WASHINGTON, BY

DAVID K. MULLIS)
Types of Monitor Configuration 5

The third water-quality monitoring system is a 

combined sensor and recording sonde that is self 

contained, requires no external power, and reduces 

exposure to vandalism. Power is supplied by conventional batteries located in a sealed compartment, and 

sensor data are stored within the sonde on nonvolatile, 

flash-memory, recording devices (fig. 3). The advantages and disadvantages of the self-contained sensor 

and recording system must be considered (table 3).

Types of Sensors

Sensors are available for continuous 

measurement of many physical properties and chemical 

constituents, but five of the most commonly used 

sensors are for the measurement of temperature, 

specific conductance, DO, pH, and turbidity.

Temperature

Temperature has an important influence on the 

density of water, the solubility of constituents in water, 

pH, specific conductance, the rate of chemical 

reactions, and biological activity in water (Radtke, 

Kurklin, and Wilde, 1998). The preferred watertemperature scale for most scientific work is the Celsius 

scale. Continuous water-quality sensors usually 

measure temperature with a thermistor, which is a 

semiconductor with resistance that changes with 

temperature. Thermistors are reliable, accurate, and 

durable sensors that require little maintenance and are 

relatively inexpensive. Modern thermistors can easily 

measure temperature to plus or minus (+) 0.1 degree 

Table 3. Principal advantages and disadvantages of the 

self-contained monitoring system.

Advantages Disadvantages

Location options are 

flexible.

Data are available only during site 

visits.

The monitor is protected 

from vandalism.

Equipment status checks are 

required.

Electrical hazards are 

nonexistent.

Servicing sensors and recovering 

data can be difficult.

Sensors are susceptible to debris or 

high flow.

Shifting channels may cause 

movement of the equipment.

Status of the equipment can be 

checked only while servicing.

If batteries die, data are lost.

Figure 3. Self-contained water-quality monitoring sensor and 

recording system. (PHOTOGRAPH: DELAWARE AND RARITAN CANAL

FEEDER AT RAVEN ROCK, NEW JERSEY, BY BONNIE GRAY)
6 Guidelines and Standard Procedures for Continuous Water-Quality Monitors

Celsius (°C), but the user must verify the accuracy 

claimed by the manufacturer for the range of 

application. Typically, temperatures are reported to the 

nearest 0.5 °C because the thermistor is located at one 

point, which may not be representative of the entire 

body of water being measured. 

Specific Conductance

Specific conductance is a measure of the 

capacity of water to conduct an electrical current and is 

a function of the types and quantities of dissolved 

substances in water (Radtke, Davis, and Wilde, 1998). 

As concentrations of dissolved ions increase, specific 

conductance of the water increases. Specific 

conductance measurements are a good indication of 

total dissolved solids and total ion concentrations, but 

there is no universal linear relation between total 

dissolved solids and specific conductance. A 

continuous record of specific conductance can be used 

in conjunction with chemical analyses and continuous 

discharge records to estimate constituent loads (Clifton 

and Gilliom, 1989; Hill and Gilliom, 1993; Christensen 

and others, 2000). The USGS measures specific 

conductance at or compensated to 25 °C and reports 

specific conductance in microsiemens per centimeter at 

25 °C (μS/cm at 25 °C). 

Specific conductance sensors are one of two 

types—contact sensors with electrodes and sensors 

without electrodes. Continuous water-quality sensors 

generally have electrodes that require the user to 

choose a cell constant for the expected range of 

specific conductance. Multiparameter monitoring 

systems usually contain automatic temperature 

compensation circuits; thus, specific conductance 

usually is compensated to 25 °C, but this should be 

verified by checking the manufacturer’s instruction 

manual. All modern monitoring systems are designed 

for medium-strength specific conductance waters 

(100 to 2,000 μS/cm at 25 °C) or higher. In general, 

specific conductance electrodes are reliable, accurate, 

and durable but are susceptible to fouling from aquatic 

organisms and sediment. 

Dissolved Oxygen

The DO concentration in surface water is related 

primarily to atmospheric reaeration and photosynthetic 

activity of aquatic plants (Radtke, White, and others, 

1998). The range of observed DO in surface waters 

typically is from 2 to 10 milligrams per liter (mg/L) at 

20 °C. The value for 100-percent saturation of DO 

decreases with increased temperature and increases 

with increased atmospheric pressure. Occasions of 

excess oxygen (supersaturation) often are related to 

extreme photosynthetic production of oxygen by 

aquatic plants as a result of nutrient (nitrogen and 

phosphorus) enrichment, sunlight, and low-flow 

conditions. Occasions of saturated oxygen commonly 

are related to cascading flow conditions, both natural 

and artificial. DO may be depleted by inorganic 

oxidation reactions or by biological and chemical 

processes that consume dissolved, suspended, or 

precipitated organic matter (Hem, 1989). DO is a 

significant factor in chemical reactions in water and the 

survival of aquatic organisms.

The most commonly used technique for 

measuring DO concentrations with continuous waterquality sensors is the amperometric method, which 

measures DO with a temperature-compensated polarographic membrane-type sensor. While polarographic 

membrane-type sensors generally provide accurate 

results, they commonly are sensitive to temperature 

and water velocity and are prone to fouling. Because 

the permeability of the membrane and solubility of 

oxygen in water change as functions of temperature, it 

is critical that the DO sensors be temperature 

compensated. 

The measuring process consumes DO; therefore, 

water flow past the sensor is critical. If water velocity 

at the point of measurement is less than 1 foot per 

second (ft/s), an automatic or manual stirring 

mechanism or a different measurement technique is 

required. DO sensors are prone to inaccuracies from 

algal fouling, sedimentation, low velocity, and very 

high velocities. A complete discussion of DO 

calibration, measurement, and limitations can be found 

in Radtke, White, and others (1998). 

pH

The pH of an aqueous solution is controlled by 

interrelated chemical reactions that produce or 

consume hydrogen ions (Hem, 1989). The pH of a 

solution is a measure of the effective hydrogen-ion 

concentration (activity; Radtke, Busenberg, and others, 

1998). More specifically, pH is a measure that 

represents the negative base-10 logarithm of hydrogenion activity of a solution, in moles per liter. Solutions 

having a pH below 7 are described as acidic; solutions 

with a pH greater than 7 are described as basic or 
Site Selection 7

alkaline. Dissolved gases, such as carbon dioxide, 

hydrogen sulfide, and ammonia, appreciably affect pH. 

Degasification (for example, loss of carbon dioxide) or 

precipitation of a solid phase (for example, calcium 

carbonate) and other chemical, physical, and biological 

reactions may cause the pH of a water sample to change 

appreciably soon after sample collection (Radtke, 

Busenberg, and others, 1998).

The electrometric pH measurement method, 

using a hydrogen-ion electrode, commonly is used for 

continuous water-quality pH sensors. Sensors used in 

submersible monitors typically are combination 

electrodes in which a proton (H+)-selective glass-bulb 

reservoir is filled with an approximate pH-7 buffer. A 

silver wire coated with silver chloride is immersed in 

the internal reference electrode buffer reservoir. 

Protons on both sides of the glass pH electrode (media 

and buffer reservoir) selectively interact with the glass, 

setting up an external potential gradient across the 

outer glass membrane. Because the hydrogen-ion 

concentration in the internal buffer solution is constant, 

this external potential difference across the outer glass 

membrane, which is determined relative to the internal 

silver/silver-chloride reference electrode, is 

proportional to the pH of the medium. A correctly 

calibrated pH sensor can accurately measure pH to 

+ 0.2 pH unit; however, the sensor can be scratched, 

broken, or fouled easily. Detailed instructions for the 

calibration and measurement of pH are described by 

Radtke, Busenberg, and others (1998) or by the 

instrument manufacturer.

Turbidity

 Turbidity sensors operate differently from those 

for temperature, specific conductance, DO, and pH, 

which convert electrical potentials into the measurement of the constituent of interest. A turbidity sensor 

operates by directing a light beam from a light-emitting 

diode into the water sample and measuring the light 

that scatters off the suspended particles present in the 

water. The nephelometric measurement method is used 

in most commercially available sensors with a sensor 

range of 0–1,000 nephelometric turbidity units (NTU) 

and an accuracy of + 5 percent or 2 NTU, whichever is 

greater. However, some sensors can report values 

reliably up to about 1,500 NTU.

Turbidity readings are affected by suspendedsediment particle size, entrained air bubbles, floating 

debris, and other particles in the water that may collect 

on or near the optic sensor during data collection. The 

effect of temperature on turbidity sensors is minimal, 

and the software for modern sensors provides 

temperature compensation. Calibration and 

measurement of turbidity by using a submersible 

sensor are discussed by Wilde and Gibs (1998), but 

manufacturer’s instructions and recommendations 

must be followed. Sensors that are maintained and 

calibrated routinely will be relatively error free and will 

provide valid data at all times.

Instrument Acceptance Criteria

Independent testing to ensure accuracy and 

reliability is an important part of any quality-assurance 

program for hydrologic field instrumentation. As stated 

in the Water-Resources Division (WRD) Hydrologic 

Field Instrumentation and Equipment Policy and 

Guidelines (U.S. Geological Survey WRD 

Memorandum 95-35, 1995), any USGS District, 

program, or project that procures an instrument is 

responsible for ensuring that adequate testing is carried 

out and that the documented results fully characterize 

the performance and capabilities of the instrument. One 

of the primary responsibilities of the USGS Hydrologic 

Instrumentation Facility (HIF) is the testing, 

evaluation, and documentation of instrument 

performance. Districts are encouraged to purchase 

instruments through the HIF when possible or perform 

the necessary steps of independent testing to ensure 

accuracy and reliability as stated by the instrument 

manufacturer. District personnel are encouraged to 

work with the HIF to evaluate new instrumentation and 

actively participate in the web-based instrument 

quality-assurance data base managed by the HIF by 

entering, reviewing, and overseeing District data in the 

data base and by taking corrective actions when 

necessary.

Site Selection

The location of a water-quality monitoring site is 

directly related to the purpose of monitoring and the 

data-quality objectives. Stream characteristics, 

location of the site, and other data-quality objectives 

determine whether a data sonde will be placed in situ or 

whether a flow-through receptacle with a pumping 

sampler will be a better choice. More site-specific 

considerations in monitor placement include sitedesign considerations, monitor installation, physical 

constraints, and service requirements (table 4).
8 Guidelines and Standard Procedures for Continuous Water-Quality Monitors

Balancing the numerous site considerations for 

placement of a continuous water-quality monitoring 

system is difficult. The optimum site consideration for 

achieving the data-quality objectives is placing the 

pump intake, sensor package, or sonde in a location that 

best represents the section of the water body being 

measured. Lateral mixing in large rivers, however, 

often is not complete for tens of miles downstream from 

a tributary or outfall. A location near the streambank 

may be more representative of local runoff or affected 

by point-source discharges upstream, whereas a 

location in center channel may be more representative 

of areas farther upstream in the drainage basin. 

Turbulent streamflow may aid in mixing, but turbulence 

can create problems for some monitored parameters 

such as DO or turbidity. For a medium to small stream 

with alternating pools and riffles, the best flow and 

mixing occurs in the riffle portion of the stream; 

however, flooding may change the locations of shoals 

upstream from the monitoring site, and the 

measurement point may no longer represent the overall 

water-quality characteristics of the water body.

Sufficient cross-section measurements must be 

made at the site to determine if a prospective site is 

sufficiently well mixed and to ensure that the site will 

not be subject to significant difference in a cross 

section. If significant horizontal or vertical variability is 

determined, consideration must be given to choosing 

another site or using a different approach to meet the 

data-quality objectives (see Placement of Sensors in the 

Cross Section).

Large streams and rivers may be monitored best 

from the downstream side of bridge abutments, 

assuming that safety hazards and other difficulties can 

be reduced or overcome. The measurement point in the 

vertical dimension for larger flow systems also needs to 

be appropriate for the primary purpose of the 

monitoring installation. The vertical measurement point 

can be chosen for low-, medium-, or high-flow 

conditions. 

Selection of a water-quality monitoring site is 

determined by the data-quality objectives, and the best 

location for a site is often one that is best for measuring 

surface-water discharge. Although hydraulic factors in 

site location must be considered, it is more important to 

consider factors that affect the water-quality data. It is 

important to select a site that is representative of the 

stream, and the cross-section characteristics of specific 

conductance, turbidity, or pH may be helpful in 

selecting the best sites. Assessment of a site may be 

dependent on fouling potential, high-tension power 

lines, or radio towers that may interfere with data 

collection or telemetry. The same hydraulic factors that 

are used in selecting a specific site for gaging discharge 

in a channel also can be used in selecting a waterquality monitoring location. Both purposes seek a 

representative site that approaches uniform conditions 

across the entire width of the stream. Rantz and others 

(1982) identified nine hydraulic conditions of the ideal 

gage site, and these also must be considered in site 

selection for water-quality sites (table 5).

The location of water-quality monitoring 

sensors in cold regions requires additional considerations in order to obtain data during periods of ice 

formation. White (1999) discusses environmental 

factors in the site selection of an automated waterquality station in British Columbia, Canada, but also 

generalizes morphological stream factors and the 

importance of selecting a site that has a minimal 

chance of damage or destruction from natural forces 

and a minimal source of bubbles. White also 

Table 4. Factors for consideration in the placement and 

installation of continuous water-quality monitoring systems

Site-design considerations

Representative of cross-sectional variability 

Constraints of channel configuration

Range of streamflow (from low flow to flood)

Velocity of streamflow

Turbulence

Avoidance of high-water debris damage

Range of values for water-quality physical properties

Protection from vandalism

Safety hazards

Monitor installation

Permits for installation

Type of installation

Difficulty and cost of installation

Ability to install monitor in representative location

Logistics (service requirements)

Accessibility of site

Frequency of service interval to meet data-quality objectives

Rate of fouling

Proximity to cross-section measuring location

Event related (for example, flooding event)

Proximity to electrical power or telephone service

Need for real-time reporting
Placement of Sensors in the Cross Section 9

emphasizes that a site should (1) meet minimum 

stream-depth requirements for instruments, (2) be safe 

and accessible under all conditions, and (3) be located 

to avoid the danger of vandalism. 

Placement of Sensors in the Cross 

Section

The location of a water-quality monitoring site is 

dependent on the purpose of monitoring and the dataquality objectives. In some cases, such as the location 

of a monitoring site in a lake, bay, or estuary, the 

data-quality objectives may require only point 

measurements; whereas, data-quality objectives for the 

measurement of load or flux in a large river generally 

require placement of a water-quality monitoring site at 

the most representative measurement point in the cross 

section of the stream. 

Determinations of cross-sectional variability are 

required before a monitoring site is installed to 

properly locate the most representative measurement 

point in the stream cross section and to determine if a 

cross-section correction is necessary. A minimum of 

two cross-section measurements per year is required to 

verify that no significant changes have occurred in the 

distribution of constituents across the stream. 

Documentation of vertical mixing is required at least 

annually at a minimum of two depths for all crosssection measurements. For monitoring sites that are 

operated more than 1 year, a minimum of six crosssection measurements representing different flow 

conditions is required to determine if discharge or 

seasonal changes are affecting significantly the 

distribution of constituent values in the cross section. 

By choosing a monitoring site with well-mixed 

streamflow, cross-section corrections may not be 

needed. 

Standard USGS procedure is to use either 

discharge- or area-weighted methods for selecting 

locations of the most representative measurement 

points in a cross section to ensure that chemical loads 

can be calculated correctly (Wilde and Radtke, 1998). 

The measurement point in a cross section is established 

by using either method to obtain data by using 

calibrated field instruments. Generally, a minimum of 

five increments across a large stream or river is 

sufficient to provide a discharge-weighted mean and 

establish the horizontal cross-sectional variability of 

the measured physical property. Alternatively, an areaweighted value can be determined by measuring the 

centroid of equal-width increments with calibrated 

field instruments. Generally, a minimum of 10 and a 

maximum of 20 measurement points across a large 

stream or river is sufficient to establish the horizontal 

cross-sectional variability of a physical property. 

Computations of mean physical property values for a 

large number of cells will produce a cross-section 

correction for any measurement location with good 

flow; however, as the number of cells exceed 40 or 

more, the computational precision exceeds the 

measuring precision. Examples of both area- and 

discharge-weighted field measurements are 

demonstrated by Wilde and Radtke (1998).

Table 5. Hydraulic conditions of the ideal gage site (after Rantz and others, 1982)

1. The general course of the stream is straight for about 300 feet upstream and downstream from the gage site.

2. The total flow is confined to one channel at all stages, and no flow bypasses the site as subsurface flow.

3. The streambed is not subject to scour and fill and is free of aquatic growth.

4. Banks are permanent, high enough to contain floods, and free of brush.

5. Unchanging natural controls are present in the form of a bedrock outcrop or other stable riffle for low flow and a 

channel constriction for high flow, or a falls or cascade that is unsubmerged at all stages.

6. A pool is present upstream from the control at extremely low stages to ensure a recording stage at extremely low 

flow, and to avoid high velocities at the streamward end of gaging-station intakes during periods of high flow.

7. The gaging station is far enough upstream from a confluence with another stream or from tidal effect to avoid any 

variable influence from the other stream or tide on the stage at the gage site.

8. A satisfactory reach for measuring discharge at all stages is available within reasonable proximity of the gage site. 

(It is not necessary that low and high flows be measured at the same stream cross section.)

9. The site is readily accessible for ease of installation and operation of the gaging station.

10. The site is not susceptible to manmade disturbances, nearby tributaries, or point-source discharges.
10 Guidelines and Standard Procedures for Continuous Water-Quality Monitors

The number of vertical measurements needed for 

deeper flow regimes is dependent on the degree of 

vertical mixing. If physical or chemical stratification is 

observed, the number of vertical measurements may 

need to be increased from mid-depth to two measurements (0.2 and 0.8 depth) or more. The vertical 

stratification may be sharply defined, which requires 

the measurements across the transition zone to be more 

closely spaced to represent the position and degree of 

stratification adequately. 

The most efficient means of obtaining physical 

property multiparameter measurements is with a 

multisensor monitor that can measure more than one 

physical property at each measurement point. For 

locations with higher stream velocities, point sampling 

with a heavy sampler may be necessary. Measurements 

of discrete samples from the cross section should be 

made quickly before measurable changes occur in 

some physical properties. Discrete samples should not 

be composited for measurement of cross-section 

corrections. 

In the case of pH, a median value is used for 

determining the measuring-point correction. 

Alternatively, pH values can be converted to hydrogenion concentrations (antilogarithms of negative pH) for 

computational purposes (see Appendix 1). Computed 

mean pH values tend to be more acidic than median 

values; for large flow systems with 40 or more pH 

measurements, the median and the properly computed 

mean pH values should be very close. 

Specific information about a field site (station) is 

summarized in a station description (see Appendix 2). 

The station description, which contains specific 

information about a field site location, history, and 

operation, should be placed in an appropriate field 

folder and carried into the field. Cross-section 

measurements and extreme values must be updated 

annually in the station analysis (see Appendix 3) as part 

of the data-evaluation process. For many stations with 

critical data-quality objectives, service intervals may 

be a week or less. The service interval must be included 

in the station description as well as in the report 

manuscript station description, as described by Novak 

(1985). 

Field Meter Calibration

Measurements that compare field meter physical 

property values with the continuous monitor readings 

should be made before, during, and after servicing the 

monitor to document any environmental changes 

during the service interval. Measurements are made at 

the monitoring site by using calibrated field 

instruments as close to the sensor as possible and 

within 5-minute intervals. Before site visits, all support 

field meters should be checked for operation and 

accuracy. Minimum calibration frequency is detailed 

by Wilde and Radtke (1998) for each type of meter, and 

all calibrations are recorded in the corresponding 

instrument log books. All information related to preand post-trip, National Field Quality Assurance, and 

other periodic calibrations is recorded in the instrument 

log books. 

Temperature

The proper calibration and documentation for 

thermometers and thermistor thermometers are 

detailed by Radtke, Kurklin, and Wilde (1998). The 

USGS procedures specify that thermometers be 

calibrated or checked against a National Institute of 

Standards and Technology (NIST)-certified 

thermometer, and thermistors should be accurate 

within + 0.2 °C. For both thermistors and liquid-inglass thermometers, an annual 5-point calibration over 

the temperature range of 0–40 °C is required. The 

annual 5-point check requires laboratory equipment. In 

addition, 2-point calibration checks over the maximum 

and minimum expected annual temperature range 

should be made three or more times per year for 

thermistors and two or more times per year for liquidin-glass thermometers. Calibrated thermometers and 

thermistors must be marked with the date of 

calibration.

Specific Conductance

The proper calibration and documentation for 

specific conductance meters are detailed by Radtke, 

Davis, and Wilde (1998). Standards bracketing the 

expected full range of anticipated values are used to 

calibrate the specific conductance meter to the 

appropriate units for particular field conditions. 

Calibration is performed at the field site with standards 

that have been allowed to equilibrate to the temperature 

of the water being monitored. The accuracy of the 

meter should be within 5 percent for specific 

conductance values less than or equal to 100 μS/cm, or 

within 3 percent for specific conductance values more 

than 100 μS/cm. Specific conductance standards are 
Monitor Operation 11

available from the USGS Ocala Quality Water Service 

Unit (QWSU). Standards must be discarded after use.

Dissolved Oxygen

The proper calibration and documentation for 

DO meters are detailed by Radtke, White, and others 

(1998). DO sensors measure the partial pressure of DO 

by the flow of oxygen through a porous membrane and 

oxygen consumption at a cathode. The calibrated 

accuracy of DO meters should be within the lesser of 

5 percent or + 0.3 mg/L. The accuracy of a DO meter 

at 0.0 mg/L is verified by measuring the DO of a 

sodium sulfite solution, as described by Radtke, White, 

and others (1998). Calibration of a DO meter at 100-

percent oxygen saturation is made by adjusting the 

meter reading for air saturated with water vapor to a 

value obtained from a solubility table generated from 

the equations of Weiss (1970) and listed in Radtke, 

White, and others (1998). The 100-percent saturation 

value is based on the water temperature and the 

uncorrected barometric pressure. A reliable pocket 

altimeter can be used to measure uncorrected (true) 

atmospheric pressure to the nearest 1 millimeter (mm) 

of mercury. An additional correction for salinity, based 

on temperature and specific conductance, should be 

calculated for waters that have specific conductance 

values greater than 2,000 μS/cm. Calibration and 

operation procedures differ among instrument types 

and makes, and manufacturer’s instructions must be 

followed closely. All calibration information must be 

recorded in the instrument log book.

pH

A detailed 10-step description of the calibration 

of pH meters and that covers a wide range of available 

equipment is described by Radtke, Busenberg, and 

others (1998). Calibration and adjustments for 

multiparameter sensor systems are found in the 

manufacturer’s service manuals. Accuracy of field pH 

meters should be at least + 0.1 pH unit. Two standard 

buffers bracketing the expected range of environmental 

values are used to calibrate a pH electrode, and a third 

is used as a check for linearity. The pH-7 buffer is used 

to establish the null point, and a pH-4 or pH-10 buffer 

is used to establish the slope of the calibration line at 

the temperature of the solution. The slope of a pH 

electrode is temperature sensitive, but modern sensors 

can adjust the pH slope to the observed temperatures 

through manual or automatic temperature 

compensation. It is important, however, that the 

temperatures of the buffers be as close as possible to 

the samples being measured. Immersing the pH buffer 

bottles in the surface water for about 15 minutes allows 

the stream or river temperature and the buffer 

temperature to equilibrate. Standard buffers of pH 4, 7, 

and 10 are readily available from the QWSU. All 

calibration information is to be recorded in the instrument log and on the field notes. Proper calibration of 

pH sensors for low specific conductance waters, less 

than 100 μS/cm, is described by Busenberg and 

Plummer (1987) and by Radtke, Busenberg, and others 

(1998).

Turbidity

The proper calibration and documentation for 

turbidity meters are described by Wilde and Gibs 

(1998). Calibration of a turbidity instrument by using 

Formazin or another primary standard usually is done 

in the laboratory, with instrument checks being 

performed in the field. Most sensor manufacturers 

recommend either Formazin or other approved primary 

standards, such as styrene divinylbenzene (SDVB) 

polymer standards, for calibrating turbidity sensors. 

Formazin-based standards can be diluted by using a 

dilution formula; however, errors may be introduced 

during the dilution process, thus reducing the accuracy 

of the standard solution. Formazin-based standards 

also are temperature dependent, and accurate readings 

may be difficult to obtain during field conditions. 

Wilde and Gibs (1998) suggest that the effect of 

thermal fluctuations can be minimized by calibrating 

the instrument at room temperature in an office 

laboratory using a Formazin-based standard and 

secondary standard. Instrument calibration can then be 

checked at the field site by using a secondary standard. 

Turbidity standards for various ranges are available 

commercially. Before placing the sensor in a standard, 

the sensor must be cleaned, rinsed three times with 

turbidity-free water, and carefully dried. Turbidity-free 

water is prepared as described by Wilde and Gibs 

(1998).

Monitor Operation

The operation of a water-quality monitoring 

station is intended to produce the greatest amount of 

correctable field record that can be verified. The 

general operational categories include maintenance of 
12 Guidelines and Standard Procedures for Continuous Water-Quality Monitors

the station and equipment; inspection and recording of 

sensor readings; cleaning, calibration, and troubleshooting of sensors and recording equipment; crosssection measurements; and accurate record keeping. 

Maintenance

Maintenance frequency generally is governed by 

the fouling rate of the sensors, and this rate varies by 

sensor type, hydrologic environment, and season. The 

performance of temperature and specific conductance 

sensors tends to be less affected by fouling, whereas the 

dissolved oxygen, pH, and turbidity sensors are more 

prone to fouling. The use of wiper or shutter 

mechanisms on modern turbidity instruments has 

decreased the fouling problem significantly. For 

stations with critical data-quality objectives, service 

intervals may be weekly or more often. Monitoring 

sites with nutrient-enriched waters and moderate to 

high temperatures may require service intervals as 

frequently as every third day. In cases of severe 

environmental fouling or remote locations, the use of 

an observer for servicing the water-quality monitor 

should be considered. In addition to fouling problems, 

physical disruptions (such as pump failure, recording 

equipment malfunction, sedimentation, electrical 

disruption, debris, ice, or vandalism) also may require 

additional site visits. The service needs of waterquality monitoring stations equipped with telemetry 

can be recognized quickly, and the use of satellite 

telemetry to verify proper equipment operation is 

recommended.

The general maintenance functions at a waterquality monitoring station include:

• Daily review of sensor function for sites 

equipped with telemetry

• Inspection of the site for signs of physical 

disruption

• Inspection of sensor(s) for fouling, corrosion, 

or damage

• Battery (or power) check

• Time check

• Routine sensor cleaning and servicing

• Calibration (if needed)

• Downloading of data

The specific maintenance requirements depend 

on the site configuration and equipment. A useful 

discussion of the maintenance requirements for the 

flow-through and USGS minimonitor installations can 

be found in Gordon and Katzenbach (1983), but nearly 

all operational requirements are fulfilled by the 

completion of a water-quality continuous monitor 

field-inspection form (Appendix 4). The 

manufacturer’s instructions must be followed for other 

types of equipment.

Sensor Inspection

The purposes of the sensor inspection are to 

provide an ending point for the interval of waterquality record since the last service visit, a beginning 

point for the next interval of water-quality record, and 

verification that the sensor is working properly. This is 

accomplished by recording the initial sensor readings, 

servicing the sensors, recording the cleaned sensor 

readings, performing a calibration check of sensors by 

using appropriate standards, and if the readings of the 

monitoring sensor are outside the range of acceptable 

differences (see next section, Monitor Calibration 

Criteria), recalibrating the sensor. A final 

environmental sensor reading is required after the 

calibration check or after recalibration. The difference 

between the initial sensor reading and the cleaned 

sensor reading is the sensor error as a result of fouling; 

the difference between the calibration-check reading 

and calibrated-sensor reading, if necessary, is a result 

of drift. All information related to the sensor inspection 

must be recorded on a field form or in a field notebook. 

The sensor readings in the field notes become the basis 

for corrections (shifts) during the record-processing 

stage; thus, a complete and thorough documentation of 

the sensor inspection is important.

The initial sensor readings (before cleaning) of 

the monitoring equipment are compared to a calibrated 

field meter before removing the monitor sonde for 

servicing. The comparison ideally is made at the 

measuring point in the stream. This initial sensor 

reading becomes the ending point of the data record 

since the last servicing, and the field meter reading 

provides a sense of the reasonableness of the monitor 

readings and an indication of potential drift and 

fouling. However, except for temperature sensors, the 

field meter readings are not used directly in record 

computation. The field meter is used as a tool to assess 

cross-sectional variability and environmental changes 

that may occur while the monitor is being serviced.

Upon removal from the water, the monitoring 

sensors are inspected for signs of chemical precipitates, 

stains, siltation, or aquatic growth. These observations 

are recorded in the field notes before cleaning, and the 
Monitor Operation 13

individual sensors must be cleaned according to the 

manufacturer’s specifications. The cleaned sonde or 

sensor is then returned to the stream and checked 

against the field meter. Both instrument readings are 

recorded in the field notes. The observed difference 

between the initial sensor reading and the cleaned 

sensor reading is a result of fouling (chemical 

precipitates, stains, siltation, or aquatic growth). 

Monitor Calibration Criteria

The concept of not calibrating sensors for small 

changes from a standardized value was defined by 

Gordon and Katzenbach (1983). This idea recognizes 

limits in recording electronic data under field 

conditions that are close to the operating accuracy of 

the equipment. Adjustments within these acceptable 

limits may not improve the overall data accuracy. With 

improvements in sensor technology, this acceptablelimit concept has been refined to calibration criteria for 

recording field sensors based on the stabilization 

criteria defined by Wilde and Radtke (1998) and also 

takes into consideration the lesser accuracy of some 

continuous water-quality sensors. A calibration check 

using known standards is performed on cleaned 

monitoring sensors; if the monitor sensors are outside 

the range of acceptable differences, the sensor must be 

recalibrated. If the calibration-check sensor readings 

for the monitor are within the calibration criteria 

(table 6), the monitoring sensors are considered 

checked and no further adjustments are required.

All sensor readings are recorded in the field 

notes, and all calibration information is recorded in the 

monitor instrument log. The calibrated monitoring 

sensor is returned to the stream and allowed to 

equilibrate to the stream temperature. The observed 

difference between the cleaned sensor calibrationcheck reading and the calibrated sensor reading (if 

necessary) is a result of drift. The calibrated sensor 

stream reading is the beginning observation of the new 

water-quality record interval. If the calibrated 

monitoring sensor fails to agree with the calibrated 

field meter within the calibration criteria, the faulty 

sensor must be repaired or replaced after verifying that 

the readings of the field meter are not in error (see 

Troubleshooting Procedures). The alternative is to 

replace the monitoring sonde or sensor with a 

calibrated backup unit and repair the malfunctioning 

monitor in the laboratory or return it to the 

manufacturer for repair.

Field Cleaning of Sensors

Most commercially available temperature 

sensors can be cleaned with a detergent solution and a 

soft-bristle brush. Film on the sensor that resists 

removal usually can be removed by soaking the sensor 

in a detergent and water solution (Ficken and Scott, 

1989), but the manufacturer’s recommended cleaning 

procedures should be followed carefully for 

multiparameter sensor systems.

Radtke, Davis, and Wilde (1998) recommend 

cleaning the specific conductance sensors thoroughly 

with de-ionized water before and after making a 

measurement. Oily residue or other chemical residues 

(salts) can be removed by using a detergent solution. 

Specific conductance sensors can soak in detergent 

solution for many hours without damage. Oil or 

other residues can be removed by dipping the sensor 

in a solvent or diluted hydrochloric acid solution 

(5 percent), but the manufacturer’s recommendations 

should be checked before using acid solution or 

solvents on sensors. The sensor should never be in 

contact with acid solution for more than a few minutes. 

Carbon and stainless steel sensors can be cleaned with 

a soft brush, but platinum-coated sensors should never 

be cleaned with a brush.

Routine cleaning of DO sensors includes the use 

of a soft-bristle brush to remove silt from the outside of 

the sensor, wiping the membrane with a damp towel, 

and then rinsing with de-ionized water. The sensor 

usually is covered with a permeable membrane and 

filled with a potassium chloride solution. The 

membrane is easily fouled and will need to be replaced 

at least every 30 days, or as needed. When the 

membrane is replaced, the potassium chloride solution 

Table 6. Calibration criteria for continuous water-quality 

monitors

[+, plus or minus value shown; oC, degree Celsius; μS/cm, microsiemens 

per centimeter at 25 oC; mg/L, milligram per liter; pH unit, standard pH 

unit; NTU, nephelometric turbidity unit]

Measured physical 

property

Calibration criteria for measurements

(variability should be within 

the value shown)

Temperature + 0.2 oC

Specific conductance The greater of + 5 μS/cm or + 3 percent 

of the measured value

Dissolved oxygen + 0.3 mg/L 

pH + 0.2 pH unit

Turbidity The greater of + 2 NTU or + 5 percent 

of the measured value
14 Guidelines and Standard Procedures for Continuous Water-Quality Monitors

should be rinsed out of the sensor with de-ionized 

water, followed by several rinses with potassium 

chloride solution before the sensor is refilled. The 

membrane must be replaced with care so that the 

surface of the membrane is not damaged or 

contaminated with grease and no bubbles are trapped 

beneath the membrane. The surface of the membrane 

should be smooth, and the membrane should be 

secured tightly with the retaining ring. The sensor 

should be stored in water overnight to relax the 

membrane before installation and calibration. This 

procedure normally requires either replacing the DO 

sensor or revisiting the site for calibration at a later 

date.

Inspection of the DO sensor must be noted in 

detail on the field sheet. The gold cathode of the DO 

sensor can be fouled with silver over an extended 

period of time, and a special abrasive tool usually is 

required to recondition the sensor. A fouled anode, 

usually indicated by the white silver electrode turning 

grey or black, can prevent successful calibration. As 

with the cathode, the sensor usually can be 

reconditioned as directed by the manufacturer. 

Following reconditioning, the sensor cup must be 

refilled with potassium chloride solution and a new 

membrane installed.

The pH electrode must be kept clean and the 

liquid junction (if applicable) free flowing in order to 

produce accurate pH values (Radtke, Busenberg, and 

others, 1998). The body of the electrode should be 

thoroughly rinsed with de-ionized water before and 

after use. In general, this is the only routine cleaning 

needed for pH electrodes; however, for specific cases 

of fouling or contamination, the manufacturer’s 

cleaning instructions must be followed. All cleaning 

and maintenance on the pH sensor are recorded in the 

instrument log book.

Optical sensors are extremely sensitive to 

fouling; thus, frequent maintenance trips may be 

necessary to prevent fouling of the turbidity sensor in 

an aquatic environment high in sediment build up, 

algae accumulation, larvae growth, or other biological 

or chemical debris. Mechanical cleaning devices or 

shutters that remove or prevent this build up are 

available for modern sensors. If the turbidity sensor is 

not equipped with a mechanical cleaning device that 

removes solids accumulation or a shutter that prevents 

build up on the lens before readings are recorded, 

reliable data collection will be more difficult.

Field Calibration of Sensors

A water-quality monitoring sensor or sonde 

should be calibrated in the laboratory before 

installation at a field location. Calibration in the 

laboratory or the field is done only by using standards 

of known quality. Field calibration is performed if the 

cleaned sensor readings obtained during the calibration 

check differ by more than the calibration criteria 

(table 6). Spare monitoring sondes or sensors are used 

to replace water-quality monitors that fail calibration 

after troubleshooting steps have been applied (see 

Troubleshooting Procedures). All calibration 

equipment must be kept clean, stored in protective 

cases during transportation, and protected from 

extreme temperatures.

Temperature Sensors

Modern water-quality temperature sensors are 

quite sturdy and accurate, and the manufacturers 

commonly make no provisions for field calibration of 

the temperature sensor. Monitoring temperature 

sensors generally are not calibrated, but comparisons of 

temperature readings are made by using Districtcertified thermometers or thermistors as described by 

Radtke, Kurklin, and Wilde (1998). Temperature 

accuracy is especially important because of the effect 

of temperature on the performance of other sensors. 

Before the field trip, the “District Certification” labels 

on thermometers or thermistors must be checked for 

the last date of certification and whether the 

instruments are appropriate for use in extreme field 

conditions.

The water-quality monitoring temperature 

sensor and the calibrated field thermistor are placed 

adjacent to one another, preferably in flowing water. If 

a liquid-in-glass thermometer is used, it must be the 

total-immersion type. Sufficient time for temperature 

equilibration must elapse before a reading is made. The 

two temperature sensors must be read and the 

temperatures recorded within 2 minutes. If the 

monitoring temperature sensor fails to agree within 

+0.2 °C, troubleshooting steps must be taken; if 

calibration fails, the sensor should be replaced. The 

faulty sensor or sonde should be returned to the 

manufacturer for proper calibration or repair.

Specific Conductance Sensors

If sensor inspection and cleaning processes fail 

to bring a specific conductance sensor within the 
Monitor Operation 15

calibration criteria (table 6), the sensor must be 

calibrated. Field calibration differs among the types of 

available instruments but generally relies on calibration 

with two standard solutions, bracketing the expected 

range of environmental conditions, and a third standard 

solution near the ambient specific conductance value of 

the water. All calibration information is recorded on the 

field sheet and in the monitoring instrument log.

Sensor inspection and field cleaning procedures 

must be followed to confirm that the monitor 

thermistor and the field thermistor or thermometer 

agree within +0.2 °C. Expiration dates for the standard 

solutions should be checked, and the standard solution 

bottles must be allowed to equilibrate with the stream 

temperature (by soaking 15 to 30 minutes). The sensor, 

thermistor or thermometer, and measuring container 

are rinsed three times with a standard solution that 

approximates ambient conditions. Fresh standard 

solution is poured into the measurement container; the 

temperature setting is adjusted if necessary; the 

specific conductance, the standard values, and the 

temperature are read and recorded in the field notes and 

the monitoring instrument log; and the monitor reading 

is adjusted to the standard solution value. A 

temperature correction may be necessary if the monitor 

does not have automatic temperature correction 

(Radtke, Davis, and Wilde, 1998).

The used standard solution is discarded into a 

waste container, and the procedure is repeated using 

the second and third standard solutions. The monitor 

readings for the standards are read and recorded in 

the field notes and the instrument log. If the monitor 

sensor readings differ from the standards by more 

than 5 μS/cm or 3 percent, whichever is greater, the 

calibration sequence must be repeated. If the second 

calibration sequence still differs by more than the 

calibration criteria, troubleshooting techniques will 

need to be attempted (see Troubleshooting Procedures). 

If these steps fail, the sonde or monitoring sensor must 

be replaced and the backup instrument calibrated.

Dissolved Oxygen Sensors

Dissolved oxygen in water is related to water 

temperature, atmospheric pressure, and salinity. 

Radtke, White, and others (1998) provide detailed 

calibration steps for four different procedures: (1) aircalibration chamber in water, (2) air-saturated water, 

(3) air-calibration chamber in air, and (4) iodometric 

(Winkler) titration. The first three procedures 

determine DO by an amperometric method that 

depends on diffusion of oxygen through a Teflon 

membrane. The iodometric titration measures DO 

directly by a dye color change upon reduction of 

available oxygen. The appropriate procedure depends 

on the type of monitoring equipment. Manufacturer’s 

calibration procedures should be followed closely to 

achieve a calibrated accuracy of + 0.3 mg/L DO. In 

general, calibration of DO sensors involves measuring 

DO at 100-percent saturation and measuring a zero-DO 

solution. For measured temperature and atmospheric 

pressure, the saturated DO is obtained from a table 

developed by Weiss (1970) and reproduced in Radtke, 

White, and others (1998). Ambient atmospheric 

pressure should be determined with a calibrated pocket 

barometer to the nearest 1 mm of mercury.

In sea water or brackish water, a salinitycorrection factor must be applied to the measured DO 

concentration. Manufacturer’s instructions should be 

referred to before applying a correction for saline 

waters (waters with specific conductance values 

greater than 2,000 μS/cm or chloride concentrations 

greater than 1,000 mg/L); but generally, specific 

conductance values less than 8,000 μS/cm have 

correction factors less than the calibration criteria of 

the monitoring sensor for DO. For specific 

conductance values greater than 8,000 μS/cm, refer to 

salinity correction tables developed by Weiss (1970) 

and reproduced in Radtke, White, and others (1998).

A fresh zero-DO standard solution should be 

prepared before each field trip, as described by Radtke, 

White, and others (1998). Calibration at 100-percent 

saturation in the field presents a problem because 

replacement of the Teflon membrane frequently is 

required, and the replaced membrane must be allowed 

to “relax” in water for 24 hours before calibration. One 

solution to this problem is to carry clean and serviced 

spare DO sensors, stored in water, to the field. The 

replacement DO sensors can then be calibrated in the 

field, and an interruption in the record and a next-day 

return site visit can be avoided. Direct measurement of 

ambient DO with the iodometric procedure requires 

preventing exposure of the sample to atmospheric 

oxygen, and this often makes accurate and precise field 

determinations difficult. The accuracy of this 

procedure also depends on the experience and 

technique of the data collector (Radtke, White, and 

others, 1998).
16 Guidelines and Standard Procedures for Continuous Water-Quality Monitors

pH Sensors

Field calibration of pH sensors is often a timeconsuming process that requires patience. Before going 

to the field, the field meter pH response and thermistor 

should be checked, as described by Radtke, Busenberg, 

and others (1998). Expiration dates for the pH 4, 7, and 

10 buffers should be checked, and spare monitoring pH 

sensors or backup sondes will need to be prepared in 

case replacement of field sensors is required.

Upon arrival at the field site, the tightly capped 

buffer solutions are placed in the stream to allow time 

for temperature equilibration, usually 15 to 30 minutes. 

The pH sensor is checked for physical damage and 

replaced if necessary. Sensor inspection and fieldcleaning procedures are followed as described by the 

manufacturer or Radtke, Busenberg, and others (1998). 

If the pH monitoring sensor reading exceeds the 

calibration criteria (table 6), the monitoring sensor 

should be calibrated as described by the manufacturer’s 

instructions. 

Temperature effects on pH buffer solutions vary 

with individual solutions, and the temperaturecorrection factor should be checked with the 

manufacturer. See Appendix 5 for examples of 

common pH buffer solution variances with 

temperature. The pH sensor reading should be 

standardized to the temperature-corrected pH value. 

The pH sensor, thermistor or thermometer, and 

measurement container are rinsed with pH-7 buffer 

solution, which is then discarded along with all 

subsequent rinsates in a waste container. Fresh pH-7 

buffer solution is poured into the rinsed measurement 

container, and the instruments are allowed to 

equilibrate for 1 minute before the buffer solution is 

discarded and fresh pH-7 buffer solution is poured into 

the measurement container. The solution is slowly 

stirred with the pH sensor or sonde. The temperature, 

pH, and associated millivolt reading are measured and 

recorded. This standardization process is repeated with 

fresh pH-7 buffer solutions until two successive values 

of the temperature-adjusted pH-7 readings are 

obtained.

The pH sensor, thermistor or thermometer, and 

measurement container are rinsed with de-ionized 

water, and the standardization process is repeated with 

a pH-4 or pH-10 buffer solution to establish the 

response slope of the pH sensor by choosing the buffer 

that brackets the expected range of pH values. The 

second temperature-corrected pH value, temperature, 

and millivolt readings are recorded, and the pH sensor, 

thermistor or thermometer, and measurement container 

are rinsed with de-ionized water. The pH-7 buffer 

solution is then used to rinse, fill, and check the pH-7 

calibration measurement. If the pH sensor reading is 

7 + 0.1 pH units, the slope adjustment has not affected 

the calibration. If the accuracy standard is not met, the 

calibration and slope adjustment steps must be 

repeated. If the repeated calibration and troubleshooting steps fail, the pH sensor or monitoring sonde 

must be replaced.

Once the slope adjustment step is completed 

satisfactorily, the third buffer solution can be used as a 

calibration range and linearity check. The temperature 

and pH values are read and recorded, but the + 0.1 

accuracy should not be expected to be achieved over 

the full range from pH 4 to pH 10 for a monitoring 

sensor.

Waters with specific conductance values less 

than 100 μS/cm require special low-ionic strength 

buffers and pH sensors. The extra preparations, 

precautions, and troubleshooting steps for measuring 

low-ionic strength waters are described by Busenberg 

and Plummer (1987).

Turbidity Sensors

Field inspection or calibration of the turbidity 

sensor is made by using Formazin or other approved 

primary standards and following the manufacturer’s 

calibration instructions as described by Wilde and Gibs 

(1998). Turbidity standards with various ranges are 

commercially available, and most sensor 

manufacturers recommend either Formazin or SDVB 

polymer standards for calibrating turbidity sensors. 

Formazin-based standards can be diluted by using a 

dilution formula; however, errors may be introduced 

during the dilution process, thus reducing the accuracy 

of the standard solution. Turbidity-free water, used in 

the preparation of standards, dilution, and rinsing, is 

prepared as described by Wilde and Gibs (1998). 

Sensors should first be inspected for damage, 

ensuring that the optical surfaces of the probe are in 

good condition. Before placing the turbidity sensor in 

standards, the sensor should be cleaned, rinsed three 

times with turbidity-free water, and carefully dried. If 

the readings are unusually high or erratic during the 

sensor inspection, entrained air bubbles may be present 

on the optic sensor and need to be removed. If the 

sensor readings exceed the calibration criteria (the 

greater of + 5 percent or 2 NTU) during the inspection 

process, the sensor must be calibrated by following the 
Monitor Operation 17

manufacturer’s instructions. A three-point calibration 

process is recommended, covering the expected range 

of values, although some instruments may be limited to 

calibration with only one or two standards. If the 

instrument allows only a two-step process, then two 

primary standards covering the expected range should 

be used for calibration and a third mid-point standard 

used to check for linearity. Similarly, if the instrument 

requires calibration only with turbidity-free water and 

one standard, another mid-point standard should be 

used to check for linearity.

Cross-Section Measurements

The data objectives for most continuous waterquality monitoring sites require that the sensors be 

installed in locations that are most representative of 

stream cross sections. A minimum of two cross-section 

measurements per year is required to verify that no 

significant changes in the distribution of physical 

properties have occurred. Variability in some streams 

may require more frequent measurements. For sites 

that are operated more than 1 year, a minimum of six 

cross-section measurements representing different 

seasons and flow conditions is required to determine if 

discharge or seasonal changes have significantly 

affected the distribution of constituent values in the 

cross section (see Placement of Sensors in the Cross 

Section for details). 

Troubleshooting Procedures

When a parameter cannot be calibrated with 

standard solutions, the hydrographer must determine if 

the problem resides with the monitoring sensor or with 

the monitor itself and make necessary corrections to 

ensure that the monitor is operational. The 

hydrographer should carry spare sensors and sondes so 

that troubleshooting, if necessary, can be accomplished 

at the time of the service visit. Troubleshooting in the 

field can prevent the need for extra trips and greatly 

reduce lost record and the amount of time spent in 

processing the records in the office later. A successful 

service trip results in a properly calibrated and 

operating monitor. Some of the more common 

problems that are likely to be encountered in the field 

when servicing monitors are listed in Appendix 6 to 

assist in the troubleshooting process.

Field Notes and Instrument Logs

Field notes and instrument logs are the basis for 

the accurate and verifiable computation of waterquality monitoring records. Minimum requirements in 

the field notes for water-quality monitors include the 

following items:

• Station number and name

• Name(s) of data collector(s)

• Date and times of each set of measurements

• Field meter and monitor serial or “W” numbers

• Purpose of the site visit

• Horizontal and vertical locations of sensors in 

the cross section (if applicable)

• Recorded monitor values and corresponding 

field values (initial, after cleaning, and 

final instream readings)

• Cross-section measurement data (locations of 

verticals, constituent values, and 

measurement time)

• Cross-section measurement summaries and 

corrections

• Pertinent gage-height data

• Remarks that describe channel conditions, 

condition of the sensors, and so forth

• Battery voltage of monitor at arrival and 

departure (replaced?)

• Were sensors changed or replaced? (other 

remarks or observations that may aid 

in further processing of the record)

Forms including these items encourage consistency 

and help to avoid the costly omission of critical information. A field form that constitutes a comprehensive 

checklist for data collection at many water-quality 

monitoring sites is shown in Appendix 4. Alternative 

forms should be approved by the USGS District waterquality specialist.

Each field meter and water-quality monitor has 

an instrument log book, and all pertinent information 

regarding the monitor is recorded in the instrument log 

book. One of the most significant pieces of recorded 

information is the instrument calibration—both field 

and laboratory. Calibration information can be 

recorded initially on field forms or field notebooks, but 

the information then must be copied into the instrument 

log book. The instrument log book should contain a 

complete record of all maintenance in the field, the 

laboratory, or by the manufacturer. Permanent 

instrument logs contain critical calibration and 
18 Guidelines and Standard Procedures for Continuous Water-Quality Monitors

maintenance information that document instrument 

performance throughout the useful service life of the 

instrument. Calibration log information that is 

important from a record-processing standpoint 

includes:

• Calibration dates, times, and temperatures

• Calibration standard values and lot numbers

• Initial and final monitor calibration data

• Field meter calibration values

Field notes and calibration log information should be 

clearly written, and all notations should be self explanatory. The goal is to have sufficient information for 

another individual to complete the record processing 

steps, if necessary. Clear notes simplify the record 

check and review processes.

RECORD COMPUTATIONS

The record-computation process is 

accomplished to verify the data and document its 

quality. Accurate field notes and calibration logs are 

essential in processing the record. The hydrographer 

who services the water-quality monitoring installation 

typically computes the water-quality data record; 

writes the manuscript that describes the data; updates 

the station description and station analysis; and 

prepares the data record review package.

The primary steps in processing the record are an 

initial data evaluation, application of corrections and 

shifts, application of cross-section corrections, and a 

final data evaluation. The initial data evaluation should 

begin immediately upon completion of the field trip to 

ensure that all necessary information is available and to 

check for possible instrument malfunctions that may 

not have been observed in the field. Record checks and 

review of the record confirm that the data are accurate 

and ready for publication. 

Data-Processing Procedures

The processing of water-quality monitoring 

records should be completed in a timely manner 

according to water-quality-assurance plan policies. 

Complete and accurate field notes are an important part 

of the data processing and reduce the amount of time 

required to process the data. Corrections to data should 

not be made unless the causes of errors can be validated 

or explained by information or observations in the field 

notes or by comparison to information from adjacent 

stations (Ritz and others, U.S. Geological Survey, 

written commun., 1998). Ritz and others summarize 

data processing as a process that can be classified 

in six major categories: (1) initial data evaluation, 

(2) application of corrections and shifts, (3) application 

and evaluation of cross-section corrections, (4) final 

data evaluation, (5) record checking, and (6) record 

review. The first four categories are discussed in this 

section, and the latter two categories are combined in 

the section Preparation of the Review Package.

Initial Data Evaluation

The initial data evaluation checks the success of 

the transfer of raw field data (instrument readings) to 

the office data base and provides the opportunity for 

initial checks to evaluate and correct erroneous data 

(daily, if telemetry is available). Raw field data may be 

stored in a variety of formats, depending on the 

recording equipment and the means of downloading 

data from the recording equipment. The conversion of 

raw data from a variety of recording devices into a 

standard entry format to the District data base, or 

Automated Data-Processing System (ADAPS), 

generally is accomplished with the use of an on-line 

computer program, or Device Conversion and Delivery 

System (DECODES). After entry of data into ADAPS, 

primary data tables and plots can be produced for 

review. See Appendix 7 for an example of a primary 

data table.

Sensors, recorders, transmitters, receivers, 

relays, transmission systems, or unforeseen events can, 

at times, produce unexplainable data. Data should be 

reviewed daily, if possible, to edit obviously erroneous 

data caused by data transmission problems. Data 

should be processed immediately after the service visit 

and viewed graphically. In addition to confirming the 

accurate transfer of data, this may aid in detecting 

instrument or sensor errors. Data that are missing (for 

example, because of instrument or transmission 

problems) should not be estimated, but missing data 

should be documented and no statistics should be 

calculated that involve missing data. An example in 

figure 4 of data record for a continuous specific 

conductance monitor shows truncated record at the 

default maximum setting of the data logger. 

Exceedance of the default maximum was not noticed 

during routine site visits, and because the record was 

not computed and viewed graphically after service 

visits, the truncated maximum values were not 
Data-Processing Procedures 19

observed until the end of the year. Only minimum 

values were published for the period of record with 

truncated values, and the manuscript station description 

noted that maximum values may have been exceeded 

during periods of missing record (see Data Qualification 

Statements for details). 

Great emphasis has been placed on the relation 

between variations of the five water-quality properties 

(temperature, specific conductance, DO, pH, and 

turbidity) and discharge variations, but other eventrelated changes are equally important and can be 

factored into the relation only through field experience 

and first-hand observation at a site. Some examples 

include changes in air temperature, periods of sustained 

cloud cover, chemical spills, increased photosynthesis 

(influenced by a variety of factors), increased wind 

conditions, combined sewer overflows, forest fires in 

the watershed, road construction, and ice formation.

As mentioned previously, temperature, specific 

conductance, DO, pH, and turbidity have complex 

interdependencies. Understanding these relations is a 

necessary component for accurate water-quality record 

computation. Periodically visiting the upstream 

portions of the drainage basin and keeping field notes 

on evidence of changes in land-use activities are helpful 

in explaining observed changes in water quality.

Application of Corrections and Shifts

The application of corrections and shifts allows 

data to be adjusted to compensate for errors that 

occurred during the service interval as a result of 

environmental or instrumentation effects. Three types 

of measurement-error corrections are described 

here—fouling, drift, and cross-section correction. 

Corrections only should be made to measurements 

when the type and degree of correction is known. 

Because of the complex interdependencies of 

temperature and the other measured physical 

properties, a malfunctioning thermistor can invalidate 

some or all of the other measured physical properties. 

The permeability of a DO membrane, for example, 

changes the DO concentration 3 percent for each 

temperature change of 1 °C (Wilde and Radtke, 1998). 

Specific conductance also can vary as much as 

3 percent per 1 °C. 

The sequence for determining the type and 

degree of measurement error in the field and the 

application of corrections in ADAPS generally is 

fouling, drift, and cross-section correction. If the 

deviation between actual value and sensor reading 

exceed the criterion for water-quality data shifts 

(table 7), a correction is required. The correction is a 

linear interpolation over the time between sensor 

inspections.

Figure 4. Specific conductance at Duwamish River at Tukwila, Washington, 

September 5–10, 1998.
20 Guidelines and Standard Procedures for Continuous Water-Quality Monitors

The same measurement criteria used to determine 

the need for calibration (table 6) are used to determine 

the need for water-quality data shifts. In general, shifts 

are required when the deviation between actual and 

recorded data exceed the shift criteria listed in table 7.

The allowable limits shown in table 7 are 

minimal requirements. More stringent requirements 

may be required to meet the data objectives of the 

project or particular hydrologic and chemical 

environments and are determined at the discretion of 

the project chief or District water-quality specialist. 

The example of graphic corrections in Appendix 

8 shows two standards that exceed the shift criteria. 

Deviation from the value of the third standard does not 

exceed the shift criteria, but the shifted values also are 

shown if shifts were made for the third standard. The 

quality of data is excellent whether or not the shift is 

made (see Publication Criteria section); thus, shifting the 

data does not improve the data. Decisions for data shifts 

and corrections must be resolved by the hydrographer 

and members of the review team.

Decisions about the costs of more frequent 

service visits compared to the decrease in accuracy and 

precision in the record must be considered carefully for 

every water-quality monitoring site for various seasons 

and flows. It generally is understood that the more 

publishable record there is for a site, the more 

consistently the data objectives can be met for accuracy 

and precision. So it follows that it may take some time 

to finalize the appropriate service intervals at new 

installations.

Table 7. Criteria for water-quality data shifts

[+, plus or minus value shown; oC, degree Celsius; μS/cm, microsiemens 

per centimeter at 25 oC; mg/L, milligram per liter; pH unit, standard pH 

unit; NTU, nephelometric turbidity unit] 

Measured physical 

property

Shift criteria

 (apply shift when deviation exceeds this 

value)

Temperature (may 

affect the other 

physical properties)

+ 0.2 oC

Specific conductance The greater of + 5 μS/cm or + 3 percent 

of the measured value

Dissolved oxygen + 0.3 mg/L 

pH + 0.2 pH unit

Turbidity The greater of + 2 NTU or + 5 percent 

of the measured value

Fouling

Fouling may result from several sources and also 

may be event-related. Identification of electronic drift 

or loss of sensor sensitivity should be distinguished 

from fouling drift, if at all possible. The degree of 

fouling is determined from the difference between 

sensor measurements before and after the sensors are 

cleaned. 

Modern temperature sensors are sturdy, 

dependable, and resistant to fouling. Fouling has the 

least effect on temperature sensors, which is fortunate 

because modern sensor packages use internal thermistors to provide continuous temperature corrections to 

specific conductance, DO, pH, and turbidity values, all 

of which are temperature dependent.

Specific conductance sensors can be affected by 

fouling problems when mineralization, severe 

sedimentation (for example, during the recession period 

of a flood), or aquatic growth occurs. In general, the 

sensors are sturdy, easy to clean, and the calibrated field 

meters are reliable. The specific conductance correction 

for fouling generally is a datum correction.

Dissolved oxygen sensors are susceptible to 

fouling of the Teflon membrane, loss of elasticity of the 

membrane, and chemical alteration of the cathode–

anode measuring electrodes. Fouling of the membrane 

can include coating from organic or oily substances, 

siltation, attachment of aquatic organisms (for example, 

barnacles in estuarine locations), growth of algae, or 

deposition of other materials. Replacement of the 

sensor membrane is simple but requires calibration and 

eliminates the ability to distinguish drift from fouling. 

The reconstruction of reliable record ranges from 

straight forward (for example, onset of a flood) to 

complex (for example, gradual growth of an algal 

coating). The DO error correction for the appropriate 

part of the service interval generally is by use of a 

datum correction in ADAPS.

Chemical alteration of the DO electrodes can be 

caused by either a strong oxidizing or reducing 

chemical agent, such as in a spill situation, a metal-rich 

drainage basin, or organic-rich waters, such as a 

wetland. A more common alteration is sulfide 

poisoning over a longer period of time. Poisoning 

would be corroborated by chronically low dissolvedoxygen readings, even after sensor membrane replacement. For many investigations, sulfide poisoning 

usually is evident as a grey or black color on the silver 

anode.
Data-Processing Procedures 21

Continuous records of DO and turbidity are often 

the most difficult to maintain within acceptable limits 

for accuracy and precision. Because of this, the time 

period between service visits may need to be shortened 

to maintain the quantity and quality of the DO or 

turbidity record. Sensor fouling, as a result of 

biological or chemical particles accumulating on the 

sensors, can occur on any monitor left in the stream for 

a period of time. Although fouling frequently begins as 

soon as the monitor is placed in the stream for 

deployment, a rise in gage height generally will 

contribute more to fouling overall. If a turbidity probe 

is equipped with wiper or shutter technology and is 

properly maintained, the need for a fouling correction 

will be minimized. The optic mechanism on the 

turbidity sensor is extremely sensitive to build up; if the 

probe is not equipped with wiper or shutter technology, 

accuracy of turbidity data will be impaired significantly. A fouling shift generally is applied as a datum 

correction from either the last time the sensor was 

cleaned, from the last rise in gage height, or from a 

significant event noted in the field notes. 

Fouling of a pH sensor can be similar to the 

fouling of a DO membrane. The pH sensor must be 

cleaned delicately in order to avoid scratching the glass 

surface, which would render it useless. The before- and 

after-cleaning measurements of pH are critical because 

the chance of sensor drift is higher for pH than for the 

other four sensors. Distinction between drift and 

fouling in the field may be difficult; since replacement 

of a pH sensor is often required as a troubleshooting 

step, it may not be possible to distinguish drift from 

fouling. Accurate instrument log information on pH 

monitors is vital in recognizing sensor as opposed to 

monitor malfunctions.The consequence in ADAPS is a 

single datum correction for both drift and fouling. The 

preferred method of correction in ADAPS is the 

variable shift program. 

Drift

A calibration drift is an electronic drift in the 

equipment from the last time it was calibrated and is 

determined by the difference between readings of a 

cleaned sensor in standards or buffers and a calibrated 

sensor. If, after checking, the deviation from calibrations is within the calibration criteria of the sensor 

(table 6), then no sensor drift is present. Drift is 

assumed to occur at a constant rate across the service 

interval. If the sensor readings exceed the shift criteria 

(table 7), then the correction is a linear interpolation 

over the time between calibration checks. This is called 

a prorated shift in ADAPS (Bartholoma, 1997) and is 

illustrated for temperature in figure 5.

The Automated Data-Processing System 

(ADAPS) does not have an option for recording the 

percentage of shift by recorded value, but it does have 

a provision that allows three standards to be entered as 

value adjustments for a measured parameter. 

Corrections to the record can thus be applied as a 

3-point variable shift in ADAPS. This value-dependent 

adjustment is called a variable shift and is applied in 

situations where standards at the beginning and ending 

of the service interval have different amounts of 

deviation (variable shifts). The equivalent situation 

Figure 5. Generalized graph of corrections to continuous temperature record.
22 Guidelines and Standard Procedures for Continuous Water-Quality Monitors

for computation of streamflow in ADAPS is called a 

V-shift (Bartholoma, 1997). A graphic representation 

of a variable shift for specific conductance is shown in 

Appendix 8.Variable shifts can be accomplished for 

any parameter, and this is the recommended technique 

for corrections related to instrument drift. Because 

three standards frequently are used for monitor 

calibration, the variable shift is the preferred method of 

correction for drift (see Appendix 8).

The treatment for suspected sensitivity loss is 

sensor reconditioning or replacement. The pH sensors 

are particularly prone to sensitivity loss (Busenberg 

and Plummer, 1987). Sensitivity loss in the pH sensor 

may result from a partially clogged reference electrode 

junction or a change in the concentration of the 

potassium chloride filling solution. Distinguishing 

between pH sensor drift and electronic drift is possible 

by determining the sensor slope; however, the 

correction is the same. Improvements in electronic 

devices in the past two decades have greatly reduced 

the amount of true electronic drift. 

Evaluation and Application of Cross-Section 

Corrections

The purpose of cross-section corrections is to 

adjust the measurements of the monitoring equipment 

to reflect conditions more accurately in the entire 

stream cross section, from bank to bank and surface to 

bottom. The principal value of such adjusted 

measurements is realized when concurrent discharge 

measurements permit the computations of constituent 

loads transported past the station. Primary tables and 

plots from ADAPS that represent drift and fouling 

corrections should be made before the application of 

corrections to the cross section. The application of 

cross-section corrections is intended to improve the 

accuracy and representativeness of monitoring 

measurements; however, cross-section corrections 

should be made only if the variability in the cross 

section exceeds the shift criteria. 

Corrections to the cross section are based on 

field measurements taken both horizontally and 

vertically in the stream cross section. Shared 

characteristics of the specific corrections for 

temperature, specific conductance, DO, pH, and 

turbidity are that they may differ from each other at 

each site, and they all are site dependent and may be 

discharge and seasonally dependent as well. Several 

considerations govern the use of corrections. Crosssection measurements must be made under a variety of 

flow conditions (minimum of six), all seasonal 

conditions, and at least twice annually to confirm that 

the correction being applied to the water-quality 

measurements truly represents the median or mean 

cross-section values. Corrections should not be applied 

to water-quality measurements beyond the range of 

discharge measurements nor during periods of 

unsteady flow. If the correction for a measured physical 

property is consistent across a range of discharges and 

seasons, then correction of the measurement values by 

simple adjustment is warranted. Seasonal changes in 

water quality may be representative of the hydrologic 

system, but they also may be a result of local 

conditions.

Often, an increase in specific conductance may 

accompany low-flow conditions in basins where 

ground water has higher specific conductance than 

surface water. It is important to consider, however, that 

during summer low-flow conditions, extremes in 

temperature, pH, and DO may be representative of 

local biological activity rather than seasonal or 

discharge-related cross-sectional variability. Professional judgment and observations in the field logs will 

assist in evaluating the need for the application of 

cross-section corrections. Continuous water-quality 

monitoring has great value in recognizing the 

interdependence of water-quality physical properties 

under varying flow regimes. Understanding these 

relations is essential in the appropriate application of 

discharge-dependent corrections. 

Final Data Evaluation

Final data evaluation consists of reviewing the 

data record, checking shifts, and making any needed 

final corrections. When completed, the data are 

verified for publication and then rated for quality. Data 

that cannot be verified or are rated as unacceptable are 

retained for record-checking and review purposes but 

are not published or stored in ADAPS. Unacceptable or 

unverified data, however, should be archived following 

established District policies.

Maximum Allowable Limits for Reporting 

Continuous Data

Systematic adoption of a standardized final dataevaluation process, including maximum allowable 

limits and publication criteria, are important 

components in finalizing District water-quality 

records. Many USGS District offices have established 

quality-control limits for shifting data. These 
Data-Processing Procedures 23

commonly are referred to as “maximum allowable 

limits.” The concept is simple—if the recorded values 

differ from the field-measured values by more than the 

maximum allowable limits, the data are not published. 

For the purpose of consistency within the USGS and to 

inform data users of the maximum allowable limits, the 

limits are established at 10 times the calibration 

criteria, except for more stringent requirements for DO 

and turbidity, for all standard continuous-monitoring, 

data-gathering activities (table 8).

The maximum allowable limits shown in table 8 

are considered minimum standards for quality, and 

Districts are encouraged to establish stricter 

requirements. Even with the establishment of 

maximum allowable limits, professional judgment by 

the hydrographer still is needed in record processing. 

For example, a decision must be made regarding at 

what point in the data-collection interval the physical 

property values exceeded the maximum allowable 

limit. In the cases of instrument drift, gradual fouling, 

or event-related fouling, reasonable judgment can be 

made as to the time in the record interval when the 

maximum allowable limits were exceeded. The 

hydrographer computing the record and the record 

reviewer must agree on this determination and note the 

time when the maximum allowable limits were 

exceeded on the station analysis sheet.

Publication Criteria

An assessment of accuracy is required for the 

publication of all continuous water-quality records. 

After the record has been evaluated for maximum 

allowable limits, one of four accuracy classifications is 

applied to each measured physical property on a scale 

ranging from poor to excellent. The accuracy rating is 

based on data values recorded before any shifts or 

corrections are made (table 9).

Additional consideration must be given to the 

amount of publishable record and to the amount of data 

that have been corrected or shifted. Missing data or 

data that do not meet the criteria for maximum 

allowable limits can have much to little or no effect on 

the accuracy of the published data, depending on the 

situation; the decision to publish the data is left to the 

professional judgment of the hydrographer. However, 

to publish a daily value for any physical property, the 

following minimum requirements apply:

1. On days when less than 100 percent of the data 

collected at a discrete fixed or varying time interval 

(unit values) are available, in order to publish a daily 

mean value, both the expected daily maximum and 

daily minimum values must be present.

Table 8. Maximum allowable limits for continuous waterquality monitoring sensors

[+, plus or minus value shown; oC, degree Celsius; mg/L, milligram per 

liter; pH unit, standard pH unit]

Measured physical 

property

Maximum allowable limits for water-quality 

sensor values

Temperature + 2.0 °C

Specific conductance + 30 percent 

Dissolved oxygen The greater of + 2.0 mg/L or 20 percent

pH + 2 pH units

Turbidity + 30 percent

Table 9. Rating continuous water-quality records

[<, less than or equal to; +, plus or minus value shown; °C, degree Celsius; >, greater than; %, percent; mg/L, milligram per liter; 

pH unit, standard pH unit]

Measured physical 

property

Ratings

Excellent Good Fair Poor

Water temperature < + 0.2 °C > + 0.2 to 0.5 °C > + 0.5 to 0.8 °C > + 0.8 °C

Specific conductance < + 3% > + 3 to 10% > + 10 to 15% > + 15 %

Dissolved oxygen < + 0.3 mg/L > + 0.3 to 0.5 mg/L > + 0.5 to 0.8 mg/L > + 0.8 mg/L 

pH < + 0.2 unit > + 0.2 to 0.5 unit > + 0.5 to 0.8 unit > + 0.8 unit

Turbidity < + 5% > + 5 to 10% > + 10 to 15% > + 15 %
24 Guidelines and Standard Procedures for Continuous Water-Quality Monitors

2. Daily maximum and minimum values may be 

published independently if they occur during the 

expected times and when the following criteria are met:

Water temperature—A minimum of 25 percent of 

the unit values is present, and flow is gradually changing or 

at a steady state.

Specific conductance—A minimum of 50 percent of 

the unit values is present, and flow is gradually changing or 

at a steady state. Consider the relation of specific 

conductance to streamflow.

Dissolved oxygen—A minimum of 25 percent of the 

unit values is present, and flow is gradually changing or at a 

steady state. Consider the temperature and pH relation.

pH—A minimum of 25 percent of the unit values is 

present, and flow is gradually changing or at a steady state.

Turbidity—A minimum of 50 percent of the unit 

values is present, and flow is gradually changing or at a 

steady state. Consider specific conductance/turbidity 

correlation. Reporting daily mean values when less than 

100 percent of the unit values is available is a judgment 

decision and generally determined by data trends. If more 

than 50 percent of the recorded data is missing, then the 

mean value should be reported as estimated.

The current station description format for the 

USGS annual data report requires a description of the 

specific service interval ratings (Novak, 1985). The 

record-rating system described in this report must be 

systematically applied to all continuous water-quality 

monitoring data published in USGS reports. Accuracy 

ratings are listed in the REMARKS section of the station 

description for USGS annual reports. The appropriate 

rating and accuracy of each water-quality monitoring 

record also must be included in the station analysis 

form (see Preparation of the Review Package).

The calculation of daily mean pH values in 

ADAPS should be discontinued in District waterquality data-collection programs and replaced by the 

calculation of median daily pH values or a more 

accurate computational approach for the calculation 

of mean pH values.The correct calculation involves the 

conversion of pH units to hydrogen-ion concentrations, 

calculation of a mean concentration value, and 

conversion back into pH units (as shown in 

Appendix 1). This additional step is mathematically 

correct but tends to bias the results toward lower pH 

values than the simpler median value.

Preparation of the Review Package

Typically, the same individual who services the 

water-quality monitoring site also computes the waterquality monitoring record, writes the water-quality 

station analysis that describes annual operation of the 

site, makes necessary changes to the station 

description, and prepares a package of auxiliary 

information to aid in the review of the record.

Record Checking

All data used in producing the final water-quality 

record should be checked thoroughly for completeness 

and accuracy before final review and publication. The 

hydrographer who is responsible for computation of 

the water-quality record should review the record, 

followed by a second check for completeness and 

accuracy by an experienced hydrographer before final 

inspection by the USGS District water-quality 

specialist or District-designated reviewer. All field data 

should be verified for accuracy of transcription from 

field sheets; all shifts should be checked to assure that 

the correct values were used for a shift; and all dates 

and numbers in the station manuscript should be 

checked for accuracy.

Station Description

All stations are required to have a station 

description that identifies the location, history, and 

operation of the station. A complete description is 

prepared for each new station and is revised only upon 

changes in location or operation. The contents of a 

continuous water-quality station description vary, but 

in addition to the minimum requirements of location, 

history, and operation of the station, the station 

description includes information on instrumentation 

and the location and placement of water-quality sensors 

(see Appendix 2).

Station Analysis

An individual station analysis is required 

annually and includes an analysis of each constituent 

monitored at a site. The purpose of the station analysis 

is to compile information annually from the field notes, 

instrument log, and station description that bear 

directly on the accuracy and completeness of the 

record. At a minimum, the station analysis must 

include the instrumentation, period of record, sampling 

procedures, special conditions, and any variations from 
Publication 25

normal procedure (see Appendix 3). In addition, the 

station analysis includes information relating to the 

accuracy of the instrumentation and the record 

produced for the year, dates that probes were changed 

or replaced, procedures and methods used in the 

calibration process, a statement of how corrections or 

shifts were applied to the data, and any unusual events 

that may have affected the record. Reasons are given 

for how data were validated or why anomalous record 

was removed or retained. Details are recorded relating 

to how and when cross-section measurements were 

made and variations throughout the cross section. 

Contents of the Review Package

The record review package includes the 

following figures, forms, or tables (examples of the 

figures, forms, or tables are included in the Appendix 

section of this report): 

1. Station description form (Appendix 2)

2. Station analysis form (Appendix 3)

3. USGS Water-Quality Monitor Field-Inspection 

Form (Appendix 4) 

4. Primary computations table from ADAPS 

(Appendix 7)

5. Annual data report draft manuscript 

(Appendix 9)

6. Annual field measurement summary form 

(Appendix 10) 

7. Water-quality variable shift correction tables 

from ADAPS (Appendix 11)

8. Datum correction value table from ADAPS 

(Appendix 12)

9. Computed (type 3) daily-values tables 

(Appendix 13)

10. Discharge hydrograph (Appendix 14)

11. Graph of individual water-quality physical 

property for review (Appendix 15)

Documentation

The methods for collecting, correcting, and 

processing continuous water-quality monitoring data 

are defined and publication standards are established. 

Systematic application of monitoring site operation, 

the record rating system, and a standard record-review 

process are part of the necessary quality assurance in 

producing and documenting complete and accurate 

water-quality monitoring records. The use of 

DECODES for data conversion and ADAPS for data 

processing ensures national consistency and a valid 

data trail. Additionally, participation in the National 

Field Quality-Assurance Program (Stanley and others, 

1998) ensures the proficiency of the analyst and the 

instruments used in making measurements.

Level of Review Required

Another individual (a senior colleague or section 

supervisor) examines the record-review package for 

completeness and accuracy. If areas of interpretation 

exist (for example, when to start or terminate a shift), a 

discussion between these two individuals is held. When 

all issues are resolved, the decisions are documented on 

the appropriate form. The completed record-review 

package is then inspected by the District water-quality 

specialist or District-designated reviewer for 

completeness and accuracy.

PUBLICATION

It is the policy of the USGS that, with only a few 

exceptions, all data collected by the USGS are 

published or made publicly available. Although paper 

reports are the traditional means of publication, data 

currently (2000) are being made available in other 

electronic formats, such as computer disks, compact 

disks-read only to memory (CD-ROMs), or the World 

Wide Web. The same requirements for checking for 

completeness and accuracy of the record apply to all 

formats of publication.

Data Reports

All nonproprietary water-quality data collected 

during the water year are published in the USGS annual 

data report, “Water Resources Data, [State name], 

Water Year ___,” or in individual project data reports. 

Approval of hydrologic data reports is in accordance 

with applicable USGS policies (Alt and Iseri, 1986). 

USGS policy (U.S. Department of the Interior, 1992) 

states that data and information are to be published; 

however, publication is not limited to paper media 

(U.S. Geological Survey, 1990; U.S. Department of the 

Interior, 1993). Electronic formats for public 

distribution include computer storage media, such as 

CD-ROM and the World Wide Web.
26 Guidelines and Standard Procedures for Continuous Water-Quality Monitors

Data Qualification Statements

The accuracy of published water-quality 

monitoring records is described by the rating of the 

record and in the Publication Criteria section 

(table 9), and the accuracy attributed to the waterquality records is indicated in the REMARKS paragraph 

of the manuscript station description (Appendix 9). 

Different accuracies may be attributed 

to different parts of a given record.

ARCHIVING OF RECORDS

According to USGS policy, all original data that 

are published or support published scientific analyses 

are to be archived (Hubbard, 1992; U.S. Geological 

Survey, 1992). Original data—from automated datacollection sites, laboratories, outside sources, and 

nonautomated field observations—are unmodified data 

as collected or received and in conventional units 

(engineering units, generally with a decimal). Original 

data should be preserved in this form, no matter how 

they may be modified later (Hubbard, 1992). Recent 

USGS policy (U.S. Geological Survey, 1999) reaffirms 

the requirement of preserving original unaltered field 

data, and further requires that the data be preserved in 

computer-readable (electronic) digital format. In 

addition, paper copies of digital field-recorded timeseries data are no longer required. All personnel 

responsible for the collection, analysis, manipulation, 

and storage of water-quality monitoring data should 

ensure that the specified requirements of archiving 

original electronic data are implemented.

In addition to electronic field data, original 

water-quality monitoring data on paper may include 

field notes, field measurements, calibration notes, 

analytical service requests, and water-quality analytical 

printouts. These data are archived when the project is 

completed or terminated, or if data are more than 7 

years old. It is the responsibility of the District Chief to 

ensure that project files are entered into the District 

archive and are organized and complete. The District 

archive is well documented and maintained by 

specified personnel in the District.

SUMMARY

Recording systems that measure physical and 

chemical water-quality properties at discrete time 

intervals provide a nearly continuous record of water 

quality. A common configuration is the four-property 

water-quality monitoring system that collects 

temperature, specific conductance, dissolved oxygen, 

and pH data, although systems can be configured to 

measure other properties such as turbidity or 

chlorophyll. The sensors that are used to measure these 

water properties require careful field observation, 

cleaning, and calibration. Producing an accurate final 

record requires thorough procedures for the 

computation, publication, and archiving of the data. 

This report provides guidelines for U.S. 

Geological Survey site-selection considerations, sensor 

test methods, field procedures, error correction, data 

computation, and review and publication processes. 

Emerging sensor technology is broadening the variety 

of measurable chemical constituents and will continue 

to lower the limits of detection. Recent improvements 

have been made in our ability to make near real-time 

water-quality monitoring data available through the 

World Wide Web. This progress will improve 

applications and allow quality-control procedures to be 

refined.

SELECTED REFERENCES

Alt, D.F., and Iseri, K.T., 1986, Water Resources Division 

publications guide, v. 1, Publications policy and text 

preparation: U.S. Geological Survey, Water Resources 

Division, 1986 ed., 429 p.

Bartholoma, S.D., comp., 1997, User’s manual for the 

National Water Information System of the U.S. 

Geological Survey, chap. 3., Automated data 

processing system: U.S. Geological Survey Open-File 

Report 97-635, 219 p.

Busenberg, Eurybiades, and Plummer, L.N., 1987, pH 

measurement of low-conductivity waters: U.S. 

Geological Survey Water-Resources Investigations 

Report 87-4060, 22 p.

Christensen, V.G., Jian, X., and Ziegler, A.C., 2000, 

Regression analysis and real-time water-quality 

monitoring to estimate constituent concentrations, 

loads, and yields in the Little Arkansas River, SouthCentral Kansas, 1995–99: U.S. Geological Survey 

Water-Resources Investigations Report 00-4126, 

36 p.

Clifton, D.G., and Gilliom, R.J., 1989, Sources and 

concentrations of dissolved solids and selenium in the 

San Joaquin River and its tributaries, California, 

October 1985 to March 1987: U.S. Geological Survey 

Water-Resources Investigations Report 88-4217, 33 p.
Selected References 27

Ficken, J.H., and Scott, C.T., 1989, Operating manual for 

the U.S. Geological Survey minimonitor—Analogvoltage model: U.S. Geological Survey Open-File 

Report 89-403, 55 p.

Gordon, A.B., and Katzenbach, Max, 1983, Guidelines for 

use of water-quality monitors: U.S. Geological Survey 

Open-File Report 83-681, 94 p.

Hem, J.D., 1989, Study and interpretation of the chemical 

characteristics of natural water: U.S. Geological Survey 

Water-Supply Paper 2254, 264 p.

Hill, B.R., and Gilliom, R.J., 1993, Streamflow, dissolved 

solids, suspended sediment, and trace elements, San 

Joaquin River, California, June 1985–September 1988: 

U.S. Geological Survey Water-Resources 

Investigations Report 93-4085, 21 p.

Hubbard, E.F., 1992, Policy recommendations for 

management and retention of hydrologic data of the 

U.S. Geological Survey: U.S. Geological Survey OpenFile Report 92-56, 32 p.

Novak, C.E., 1985, WRD data reports preparation guide: 

U.S. Geological Survey, Water Resources Division, 

1985 ed., 289 p.

Radtke, D.B., Busenberg, Eurybiades, Wilde, F.D., and 

Kurklin, J.K., 1998, pH, in Wilde, F.D., and Radtke, 

D.B., eds., 1998, Field measurements, in National field 

manual for the collection of water-quality data: U.S. 

Geological Survey Techniques of Water-Resources 

Investigations, book 9, chap. A6.4, 27 p.

Radtke, D.B., Davis, J.V., and Wilde, F.D., 1998, Specific 

electrical conductance, in Wilde, F.D., and Radtke, 

D.B., eds., 1998, Field measurements, in National field 

manual for the collection of water-quality data: U.S. 

Geological Survey Techniques of Water-Resources 

Investigations, book 9, chap. A6.3, 22 p.

Radtke, D.B., Kurklin, J.K., and Wilde, F.D., 1998, 

Temperature, in Wilde, F.D., and Radtke, D.B., eds., 

1998, Field measurements, in National field manual for 

the collection of water-quality data: U.S. Geological 

Survey Techniques of Water-Resources Investigations, 

book 9, chap. A6.1, 15 p.

Radtke, D.B., White, A.F., Davis, J.V., and Wilde, F.D., 

1998, Dissolved oxygen, in Wilde, F.D., and Radtke, 

D.B., eds., 1998, Field measurements, in National field 

manual for the collection of water-quality data: U.S. 

Geological Survey Techniques of Water-Resources 

Investigations, book 9, chap. A6.2, 38 p.

Rantz, S.E., and others, 1982, Measurement and 

computation of streamflow: Volume 1. Measurement of 

stage and discharge: U.S. Geological Survey WaterSupply Paper 2175, 284 p.

Stanley, D.L., Boozer, T.M., and Schroder, L.J., 1998, 

Summary of the U.S. Geological Survey National Field 

Quality-Assurance Program from 1979 through 1997: 

U.S. Geological Survey Open-File Report 98-392, 11 p.

U.S. Department of the Interior, 1992, Department of the 

Interior Geological Survey Manual, v. 3, 500.14.1, 3 p.

———1993, Department of the Interior Geological Survey 

Manual, v. 3, 500.24.1, 4 p.

U.S. Geological Survey, 1990, Policy for release of digital 

data: Water Resources Division Memorandum No. 

90.30 [deleted], accessed August 14, 2000, at URL 

http://wwwoper.er.usgs.gov/memos/delete/

wrd90.030Delete.txt.

———1992, Policy for management and retention of 

hydrologic data of the U.S. Geological Survey: Water 

Resources Division Memorandum No. 92.59, accessed 

August 11, 2000, at URL http://water.usgs.gov/admin/

memo/WRD/wrd92.059.html.

———1995, Transmittal of an instrumentation plan for the 

Water Resources Division and the Water Resources 

Division hydrologic field instrumentation and 

equipment policy and guidelines: Water Resources 

Division Memorandum No. 95-35, accessed August 8, 

2000, at URL http://water.usgs.gov/public/admin/

memo/WRD/wrdpolicy95.035.html.

———1999, Preservation of original digital field-recorded 

time-series data: Water Resources Division 

Memorandum No. 99.33, accessed August 11, 2000, 

at URL http://water.usgs.gov/admin/memo/WRD/

wrd99.33.html.

Weiss, R.F., 1970, The solubility of nitrogen, oxygen, and 

argon in water and seawater: Deep Sea Research, v. 17, 

no. 4, p. 721–735.

White, E.T., comp., 1999, Automated water quality 

monitoring field manual: British Columbia, Canada, 

Ministry of the Environment Lands and Parks, Water 

Management Branch for the Aquatic Inventory Task 

Force Resources Inventory Committee, Version 1.0 

[June 8, 1999], 61 p. 

Wilde, F.D., and Radtke, D.B., eds., 1998, Field 

measurements, in National field manual for the 

collection of water-quality data: U.S. Geological 

Survey Techniques of Water-Resources Investigations, 

book 9, chap. A6 [variously paged].

Wilde, R.F., and Gibs, Jacob, 1998, Turbidity, in Wilde, F.D., 

and Radtke, D.B., eds., 1998, Field measurements, in

National field manual for the collection of water-quality 

data: U.S. Geological Survey Techniques of WaterResources Investigations, book 9, chap. A6.7, 30 p.
28 Guidelines and Standard Procedures for Continuous Water-Quality Monitors

Appendixes
Appendixes 29

Appendix 1—Example for calculation of average pH

Converting to appropriate [H+]

Daily maximum pH = 8.0 pH 8.0 = 0.00000001 [H+]

Daily minimum pH = 6.0 pH 6.0 = 0.00000100 [H+]

Average pH (inaccurate) = 7.0 Average = 0.000000505 [H+]

Average (correct) = antilog = pH = 6.32
30 Guidelines and Standard Procedures for Continuous Water-Quality Monitors

Appendix 2—Station description 

_____________________________________________________________________________________

Appendix 2A—Contents of a station description

Specific information about a field site (station) is summarized in a station description. The description 

should include:

1. Location of station

2. Station history

3. Drainage area (including basin characteristics)

4. Station description, equipment, and benchmarks

5. Discharge and monitor measurements methods and historical extremes

6. Cross-section measurements (discharge and water-quality)

7. Purpose and cooperation

8. Maps, photographs, and permits

9. Safety hazards, detailed road log, and access remarks

Appendix 2B—Example of a station description for the Columbia River at Beaver Army 

Terminal near Quincy, Oregon

 U.S. DEPARTMENT OF THE INTERIOR

GEOLOGICAL SURVEY 

WATER RESOURCES DIVISION

Original prepared 12-23-91 by K.K. Lee

revised 2-17-2000 by R.L.Kittelson

Description of Gaging Station

14-2469.00 Columbia River at Beaver Army Terminal nr Quincy, OR

LOCATION: Lat 46 o10'55", Long 123 o10'50", in NE1/4 sec 16, T.8 N., R.4 W., Columbia County, in an 

unused warehouse on 1600 ft long dock operated and maintained by Portland General Electric.

HISTORY: Stage data collected May 1968 to June 1970, Feb. 1991 to present. Stork Servex Surflow Mark 

4 UVM (Ultrasonic Velocity Meter) installed June 1991. ORE Accusonic Model 7300 UVM installed 

Apr. 1997.

DRAINAGE AREA: 256,900 sq mi.

GAGE ON DOCK (LEFT BANK): Stage and velocity sensing equipment housed in room at warehouse. 

Data is recorded on a Campbell Scientific CR10X data logger. Data logger is connected to modem 

(phone number 503-728-2376). USGS computer downloads data from data logger on a daily 

schedule. 

A. Stage: An 18 inch diameter corrugated pipe well is attached to a wood piling directly under the 

gage house floor. The top of the well is at approximately 20 ft gage datum. The bottom of the well 
Appendixes 31

is capped and at elevation -1.0 ft gage datum. Several holes along the length of the well provide 

communication. An SDI-12 shaft encoder with float/tape system senses stage in the well and is 

recorded by the data logger. Range is -1.0 to +14 ft. Gage is referred to an electric tape gage (index 

elevation 22.672 ft gage datum, 23.192 ft sea level, from levels of 9-15-99) on the instrument shelf, 

RP1, or a staff gage (0 - 13.5 ft) at the downstream end of the dock.

B. Velocity (Stork Servex Surflow Mark 4 UVM): Four transducers with a frequency of 100 KHZ 

are located in a crossed path configuration.

Left bank transducers are located on the upstream and downstream ends of the dock. Cables run 

under the dock surface and are wired directly into the UVM console. A junction box is located 

above high water near each transducer. Transducers are attached to an aluminum carriage that can 

be raised and lowered from the water surface. The carriages roll inside an aluminum channel track, 

which are bolted to the wooden dock pilings. The top of the upstream aluminum channel is at 

approximately 12 ft gage datum, extends down to -25.5 ft gage datum, and the transducer is 

positioned at -21 ft gage datum. The top of the downstream aluminum channel is at approximately 

10 ft gage datum, extends down to -27 ft gage datum, and the transducer is positioned at -25 ft gage 

datum.

 Right bank transducers are mounted on a 3 pile steel dolphin near the right bank, across the river 

from the dock. Transducer cables run up the piling to a responder, which relays signals received 

from the left bank transducers. There is no hard wire link across the channel. Transducers are 

attached to an aluminum carriage and can be raised and lowered from the water surface. Right bank 

transducer carriages roll along the face of the ‘H’ piling. The top of the piling is at approximately 

25 ft, and the bottom at -35 ft. Total length at piling is 90 ft. These transducers are positioned at 

approximately -25 ft gage datum.

Path length and angles (determined 2-4-97):

Line 1: Upstream Oregon side. Length = 1906.4 ft, angle = 56.6o.

Line 2: Downstream Oregon side. Length = 1770.7 ft, angle = 69.9o.

Combined length = 3677.1 ft, combined angle = at 63.3o

.

C. Velocity (ORE Accusonic Model 7300 UVM): Two transducers, with a frequency of 200 khz, 

located inside the piling area of the 1600 ft long dock, sense velocity in a ‘short path’. Transducers 

are wired directly into the UVM console which is located in the gage house, cables are threaded 

through the underside of the dock. The UVM’s SDI-12 output sends velocity data in feet per second 

to the CR10.

 The upstream transducer is attached to shoreward side of dock piling, is located 160 ft 

downstream of gage house (cable length 190 ft), and is aimed in a shoreward/downstream direction. 

The downstream transducer is attached to upstream dock piling on downstream end of dock, is 

located 450 ft downstream and 250 ft streamward (cable length 735 ft), and is aimed in a 

streamward/upstream direction. The angle of the transducers in relation to the dock is 33o

, path 

length is 386 ft (determined 4-10-97). Transducers are attached to 2 inch aluminum pipe which can 

be raised/lowered by sliding through pipe brackets, both transducers are positioned at 

approximately -4.0 ft gage datum. The transducer pipe brackets are accessible from a wood 

boardwalk which is below the road surface of the dock. 

GAGE ON PILING (RIGHT BANK): Water temperature/conductance sensor and 2 transducers (Stork 

UVM) attached to 3 pile steel dolphin near right bank across from dock. CR10X data logger, 

modem, cell phone (phone number 503-784-0136) and Stork Surflow UVM responder housed in a 

1ft X 3ft X 4ft metal enclosure. Data logger records data from sensors. USGS computer downloads 

data from data logger on a daily schedule.
32 Guidelines and Standard Procedures for Continuous Water-Quality Monitors

A HIF temperature/conductance probe is mounted on the upstream piling near the right bank 

side, in the main flow on the Washington side of the River. 

BENCH MARKS: Levels last run 9-15-99. 

BM 6 - could not be found at time of levels on 9-15-99, consider it destroyed.

RM 1 - could not be found at time of levels on 9-15-99, consider it destroyed.

TBM 2 - head of a 5/8" carriage bolt which attaches the guard curb to the dock roadway near the 

gage. The bolt is 3 ft streamward from the NW corner of the building which houses the gage, 

established 1966. Elevation 20.540 ft gage datum, 21.060 ft sea level. Used as the base RM for 

9-15-99 levels.

RM 3 - NE corner (painted yellow) of square concrete pedestal of overhead light fixture 40 ft 

shoreward and 5 ft downstream from downstream corner of west end of dock, and 37 ft shoreward of 

RM 4, established 9-15-99. Elevation 20.690 ft gage datum, 21.210 ft sea level, from 9-15-99 levels.

RM 4 - NE corner (painted yellow) of square concrete pedestal of overhead light fixture, 3 ft 

shoreward and 5 ft downstream from downstream corner of west end of dock, established 9-15-99. 

Elevation 21.205 ft gage datum, 21.725 ft sea level, from 9-15-99 levels.

RP 1 - head of 1/2 inch lag bolt painted yellow in side of walkway 18 ft downstream and 4 ft 

shoreward of TBM 2, established 9-15-99. This RP can be used as a tape down to water surface. 

Elevation 19.423 ft gage datum, 19.943 sea level, from 9-15-99 levels.

Datum of gage is 0.52 ft above mean sea level.

DISCHARGE MEASUREMENTS: Made by Acoustic Doppler Current Profiler (ADCP) with boat at 

section 1000 - 1500 ft downstream from gage, and just below dock. Hazards occur from floating 

debris, particularly at high flow. During low flow, measurement times should be coordinated with the 

tide cycle for steady flow.

FLOODS: Maximum daily discharge 864,000 cfs Feb. 10, 1996; maximum gage height 13.33 ft Feb. 9, 

1996.

POINT OF ZERO FLOW: Tide effect reverses flow during low-flow periods.

WINTER FLOW: No ice effect.

REGULATION: Flow regulated by many reservoirs in the basin.

ACCURACY: Measuring conditions are good except at extremely low velocities.

COOPERATION: U.S. Army Corps of Engineers, State of Oregon Department of Environmental Quality.

MAPS: Station can be located on Clatskanie, Oregon-Washington 15 minute 1952 USGS topographic sheet.

PHOTOGRAPHS: On file at Portland Field Office.

PERMITS: Permits from Corps of Engineers, Washington Department of Fisheries, Cowlitz County 

Washington, and Portland General Electric on file at Portland Field Office.
Appendixes 33

ROAD LOG:

Columbia River at Beaver Army Terminal nr Quincy, OR 14-2469.00

Interval Total Local

0.0 0.0 Oregon Hwy 30 at Longview Bridge

3.7 3.7 Alston Mayger Rd. Turn right.

0.2 3.9 Intersection. Turn right in front of grocery store.

6.7 10.6 Intersection Fish Station Rd. Continue on main road.

2.3 12.9 Unmarked intersection. Turn right.

1.2 14.1 Guard station. Check in. Go straight.

0.5 14.6 Boat launch.

0.3 14.9 Dock. Stilling well and AVM is in west end of large wood building. 

Go through second door from west side.

Alternate route which goes through Clatskanie, recommended when towing large boat. This route is narrow 

and winding.

0.0 0.0 Downtown Clatskanie at intersection of Hwy 30 and Nehalem St. 

Go north on Nehalem.

0.3 0.3 Intersection of 5th St. Turn left.

2.9 3.2 Intersection unmarked. Turn left.

0.3 3.5 Intersection Ritter Rd. Turn left.

 0.8 4.3 Downtown Quincy. Go straight.

1.0 5.3 Quincy fire station. Go straight.

0.3 5.6 Intersection unmarked. Turn left. This is same point on above road 

log at mile 12.9.

rlk, 2-17-2000
34 Guidelines and Standard Procedures for Continuous Water-Quality Monitors

Appendix 3—Station analysis

______________________________________________________________________________

Appendix 3A—Contents of a station analysis

Specific information about a field site (station) is summarized annually in a station analysis. The analysis 

should include:

1. Sampling location—Station, name, number, year, and constituent measure

2. Sampling equipment or instrumentation—Type of monitoring sensor(s) and recorder, location of 

sensor(s) or intakes, any other special instrumentation or features, and dates sensor(s) were 

changed or replaced.

3. Published records—State the constituent parameter that is published, as well as any data that is 

collected and not published.

4. Channel characteristics—Brief description of the composition of the channel and any unique or 

unusual features of the installation.

5. Rating—Statement as to how the digital record is interpreted to provide the published constituent 

values for the primary and final records.

6. Record—Statement of the completeness of the record. Note all missing data and include the final 

rating of accuracy for the period of record (or specific service intervals) in chronological order.

7. Calibration—State how and when the instrument was calibrated or checked and note the procedures used in the calibration process. Include statement if corrections were needed for the data.

8. Computations—Statement of how corrections were applied to the data, a list of extreme correction 

values that were applied to the recorded values during the year, and causes of the need for correction.

9. Treatment of atypical data—Any treatment of unusual or atypical data should be documented.

10. Cross-section measurements—State how and when the cross section was measured, the number of 

verticals, and the amount of variation throughout the cross section. State if the location of the sensor(s) or water-supply intake is representative of the stream.

11. Remarks—Any additional information about the site, data collected, or general statements that do 

not fit in any other section.
Appendixes 35

Appendix 3B—Example of a station analysis for temperature on the Columbia River at Beaver Army 

Terminal, near Quincy, Oregon

1999 14-2469.00

STATION ANALYSIS

TEMPERATURE

Columbia River at Beaver Army Terminal, Near Quincy, Oregon

Equipment.-- Campbell CR10X datalogger and HIF temperature/conductance probe located on the UVM 

transducer piling near the RB, in a section of the river with good velocities. On March 3, 1996 a cellphone system was installed that allows the site to be called daily between 1400 and 1430 to download 

data. Phone number is 503-784-0136.

Published records.--Daily maximum, minimum, and mean temperatures.

Primary Records.--Complete for the year.

Channel Characteristics.--The channel is approximately 1800 ft wide with depths up to 100 ft, with a 

bedrock bottom. Bradbury slough enters the river 0.3 miles upstream of the gage from the left bank. 

Under certain flow and tidal regimes, the x-section may not be well mixed on the right or left bank 

sections.

Rating.--Rating 1 was used for the entire year.

The measured temperature values ranged from 5.4 °C to 18.9 °C. The recorded temperature values 

ranged from 4.3 °C to 21.9 °C.

Calibration.-- The HIF temperature/conductance probe values were checked using Hydrolab field 

instrument. Calibration checks for the Hydrolab instruments were made using a certified NBS mercury 

thermometer.

 Calibration checks were performed, Feb. 19, 1997, Mar. 19, 1998, and July 9, 1999 for the small 

projects Hydrolab W489763, which indicated that no correction was needed. No corrections were 

made to data collected with this instrument.

Two calibration checks were performed on the Hydrolab W499764 (Oct. 21, 1997; Dec. 2, 1998), 

which indicated that no correction was needed. No corrections were made to data collected with this 

instrument.

In the 2000 WY, all Hydrolabs will be checked/logged on a more routine basis. 

For the HIF temperature/conductance probe, no calibration is possible.

Cross-sectional measurements.-- The depth and width integrated cross-sections on Aug. 24, 1998 varied by 

0.3 oC. The depth and width integrated cross-sections on Sept. 14, 1999 varied by 0.2 o

C. Width 

integrated cross-sections are made at the time of each NASQAN sampling. Cross-sectional data 

collected during sampling varied by less than 0.6 °C.

Computations.--Recorded CR10X values at the time of the cross-section are subtracted from the 

cross-section average, resulting in a computed correction to the recorded CR10X values 

(cross-section - CR10X = correction). This method takes into account the variation between the 
36 Guidelines and Standard Procedures for Continuous Water-Quality Monitors

CR10X recorded values compared to the cross-section average, and also the difference between the 

CR10X readings compared to the reference instrument (Hydrolab). Corrections varied from +0.2 °C 

to -0.2 °C, and were applied on a time-prorated basis between visits. Corrections were used as follows:

DATE/TIME SHIFT 

1998 LAST ST: 08 24 1230 -.10

11 23 1210 0.10

01 05 1130 0.10

01 25 1140 0.00

02 23 1120 -0.20

03 08 1200 -0.20

03 29 1140 0.10

04 20 1050 0.10

05 11 1120 -0.10

05 25 1110 -0.10

06 08 1120 0.10

06 22 1100 0.10

09 14 1120 0.20

2000 FIRST ST: 10 19 1130 0.20

Treatment of Atypical Data.--None found.

Remarks.--This is a NASQAN II water quality collection site. Water temperature and specific conductance 

data are furnished monthly to the USGS in Reston for publication in the National Water Conditions 

report. No discharge was available at the time the record was computed.

Douglas O. Cushman, 12-17-1999

checked by 

T.A. Herret 1/2/2000

doc, 12-17-99
Appendixes 37

U.S. GEOLOGICAL SURVEY, WRD

WATER QUALITY FIELD INSPECTION FORM

Sta. Name: Sta. No.: 

Observations Made By: 

Date: Julian Day: Watch Time: EDL Time:

EDL Time Reset? No Yes Watch Time: EDL Time:

EDL Operational? No Yes Battery Voltage Found: Volts

Program Altered? No Yes Battery Replaced? No Yes Volts

Downloaded? No Yes File Name:

Remarks:

EDL SENSOR SECTION

Std. EDL EDL EDL Sensor

Sensor or Initial Serviced Adjusted Condition

Name Field Meas. @T° @T° @T° (i.e., algae growth, silted)

Stage OG:

W. T°C

SC

SC

SC

SC Cell:

pH

pH

pH Slope:

pH Offset:

DO

DO Press: mm/Hg

DO ZERO Salinity corr.:

Turbidity ZERO Slope:

Turbidity Offset:

Sensor(s) removed from water __________HRMN Returned __________HRMN

Appendix 4—U.S. Geological Survey water-quality monitor field-inspection form
38 Guidelines and Standard Procedures for Continuous Water-Quality Monitors

Sensor(s) Maintenance Comments: 

Weather: Clear Partly Cloudy Light Medium Heavy Snow Rain Calm Light Breeze

Gusty Wind Very Cold Warm Hot Snow on Ground? No Yes _______in.

Control:

Flow:

Cross Sectional Measurements: Method: EDI, EWI, other

Meas. Location: ________ ft upstream downstream of monitor

Stream Mixing: Excellent Good Fair Poor

Observations:

Reference Meter(s) Make/Model Serial No. Corr. factor applied?

Temperature None Yes No

Conductivity None Yes No

pH None Yes No

Dissolved Oxygen None Yes No

None Yes No

None Yes No

Sta.

Ft from L. Bank 

or R. Bank Time Depth T°C pH SC DO

1

2

3

4

5

6

7

8

9

10

med.

coef.
Appendixes 39

Appendix 5.—Effects of temperature on pH standards

(refer to manufacturer’s specifications)

[°C, degrees Celsius; all pH values are in standard pH units]

Temp 

Buffer and nominal pH value

4.01 7.00 10.00

0 4.00 7.14 10.30

5 4.00 7.10 10.23

10 4.00 7.07 10.17

15 4.00 7.04 10.11

20 4.00 7.02 10.05

25 4.01 7.00 10.00

30 4.01 6.99 9.96

35 4.02 6.98 9.92

40 4.03 6.98 9.88

45 4.05 6.98 9.85

50 4.06 6.98 9.82

55 4.07 6.98 9.79

60 4.09 6.99 9.76
40 Guidelines and Standard Procedures for Continuous Water-Quality Monitors

Appendix 6—Troubleshooting problems with water-quality monitors

Symptom Possible problem Likely solution

Water Temperature

Thermistor does not read accuratelyDirty sensor Clean sensor

Erratic monitor readings Poor connections at monitor or 

sensor

Tighten connections

Monitor slow to stabilize Dirty sensors Clean sensor

Readings off scale Failure in electronics Replace sensor or monitor

Specific electrical conductance

Will not calibrate Standards may be old or contaminatedUse fresh standards

Electrodes dirty Clean with soap solution

Air trapped around sensor Thrust sensors up and down to 

expel air

Weak batteries Replace batteries

Erratic monitor readings Loose or defective connections Tighten or replace

Broken cables Replace cables

Monitor requires frequent calibrationReplace monitor

Dissolved oxygen

Meter drift or excessive time for 

monitor to stabilize

Temperature compensator has not 

equilibrated with temperature 

of stream

Wait for temperature 

equilibration

Fouled sensor Clean or recondition

Stirrer or pulse mechanism not 

working properly

Replace

Erratic monitor readings Bad connection at monitor or sensorTighten connections

Fouled sensor Clean or recondition

Monitor slow to stabilize Gold cathode tarnished Buff with ink eraser or 

recondition sensor

Fouled membrane Recondition sensor and replace 

membrane

Silver anode blackened Replace sensor and soak fouled 

sensor in 3% ammonia for 

24 hours

Monitor will not zero Zero-DO solution contains oxygenAdd additional sodium sulfite to 

zero-DO solution

Monitor will not calibrate Membrane damaged Replace membrane

Electrolyte diluted Replace membrane and 

electrolyte
Appendixes 41

pH

Meter will not calibrate Buffers may be contaminated Replace buffers

Faulty sensor Replace

Slow response time Dirty sensor bulb Clean sensor

Water is cold or low ionic 

strength

Patience

Erratic readings Loose or defective connections Tighten

Defective sensor Replace sensor

Turbidity

Unusually high or erratic readingsEntrained air bubbles on the optical sensor.Follow manufacturer’s directions 

Damaged sensor Replace sensor

Dirty sensor Clean following manufacturer’s 

directions

Water in connections Dry connector and reinstall 

Appendix 6—Troubleshooting problems with water-quality monitors—Continued

Symptom Possible problem Likely solution
Appendix 7—Example of an ADAPS primary data table

1 UNITED STATES DEPARTMENT OF INTERIOR - GEOLOGICAL SURVEY - WATER RESOURCES DIVISION STATE 53 DIST 53  PRIMARY COMPUTATIONS OF QUALITY OF WATER DIGITAL MONITOR RECORDS  12471400 DATE PROCESSED: 08-24-2000 @ 11:23 BY kagreene  LIND COULEE WASTEWAY AT SR17 NR WARDEN, WA  (00010) WATER TEMPERATURE STORE STATISTIC(S) 00001, 00002, 00003  PROVISIONAL DATA FOR WATER YEAR ENDING SEPT. 30, 2000 TEST DIFF:****** PUNCH INTERVAL: 60 MIN

VALUES AT INDICATED HOURS

DATE MAX MIN MEAN 1 2 3 4 5 6 7 8 9 10 11 12

10-01 14.3 12.4 13.5 AM 14.0 13.7 13.4 13.1 12.9 12.6 12.4 12.4 12.4 12.7 13.1 13.4

PM 13.7 14.0 14.3 14.3 14.3 14.1 14.1 14.0 13.8 13.7 13.4 13.2

10-02 13.5 11.5 12.6 AM 13.1 12.7 12.6 12.3 12.1 11.8 11.7 11.5 11.7 11.8 12.1 12.6

PM 12.9 13.2 13.4 13.5 13.4 13.4 13.2 13.1 12.9 12.7 12.4 12.3

10-03 13.2 10.9 12.2 AM 12.1 11.8 11.7 11.5 11.2 11.0 10.9 10.9 10.9 11.2 11.7 12.1

PM 12.6 12.9 13.1 13.2 13.2 13.2 13.1 12.9 12.9 12.7 12.6 12.4

10-04 13.4 10.9 12.3 AM 12.1 12.0 11.8 11.5 11.3 11.2 11.0 10.9 11.0 11.3 11.8 12.1

PM 12.6 12.9 13.2 13.4 13.4 13.2 13.2 13.1 13.1 12.9 12.9 12.7

10-05 14.0 12.0 13.0 AM 12.6 12.6 12.4 12.3 12.1 12.1 12.0 12.0 12.1 12.4 12.7 13.2

PM 13.5 13.7 13.8 14.0 14.0 13.8 13.8 13.8 13.8 13.7 13.5 13.5

10-06 14.6 12.7 13.7 AM 13.4 13.4 13.2 13.1 12.9 12.7 12.7 12.7 12.7 13.1 13.4 13.8

PM 14.1 14.3 14.6 14.6 14.6 14.4 14.4 14.3 14.1 14.0 13.8 13.7

10-07 14.0 12.7 13.5 AM 13.5 13.4 13.2 13.1 12.9 12.7 12.7 12.7 12.7 12.9 13.1 13.5

PM 13.7 13.8 14.0 14.0 14.0 14.0 14.0 14.0 14.0 13.8 13.7 13.7

10-08 14.0 13.2 13.6 AM 13.7 13.7 13.5 13.5 13.4 13.4 13.2 13.2 13.4 13.4 13.7 13.8

PM 14.0 14.0 14.0 14.0 13.8 13.8 13.7 13.7 13.5 13.5 13.4 13.2

10-09 13.5 12.1 12.8 AM 13.1 12.9 12.7 12.6 12.4 12.3 12.1 12.1 12.1 12.3 12.6 12.9

PM 13.2 13.5 13.5 13.5 13.5 13.4 13.2 13.1 12.9 12.6 12.4 12.1

10-10 12.4 10.7 11.8 AM 12.0 11.8 11.7 11.3 11.2 10.9 10.7 10.7 10.7 10.9 11.3 11.7

PM 12.0 12.3 12.4 12.4 12.4 12.4 12.4 12.4 12.4 12.4 12.4 12.3

10-11 12.4 11.7 12.1 AM 12.1 12.1 12.0 12.0 11.8 11.8 11.7 11.7 11.7 11.8 12.1 12.1

PM 12.3 12.3 12.4 12.4 12.4 12.4 12.4 12.4 12.4 12.3 12.3 12.3

10-12 13.7 11.8 12.7 AM 12.1 12.1 12.0 12.0 12.0 11.8 11.8 11.8 11.8 12.1 12.4 12.9

PM 13.2 13.5 13.7 13.7 13.7 13.7 13.5 13.5 13.4 13.4 13.2 13.1

10-13 14.4 12.3 13.3 AM 12.9 12.9 12.7 12.6 12.4 12.3 12.3 12.3 12.4 12.7 13.2 13.7

PM 13.8 14.1 14.4 14.4 14.3 14.3 14.0 13.8 13.5 13.4 13.2 13.1

10-14 13.1 11.3 12.1 AM 12.9 12.6 12.4 12.1 12.0 11.7 11.5 11.3 11.5 11.5 11.8 12.1

PM 12.4 12.6 12.7 12.7 12.6 12.4 12.3 12.0 11.8 11.7 11.5 11.3

10-15 11.3 9.8 10.6 AM 11.2 11.0 10.7 10.6 10.4 10.1 9.9 9.8 9.9 10.1 10.4 10.7

PM 11.0 11.2 11.2 11.0 11.0 10.9 10.9 10.7 10.6 10.4 10.3 10.1

10-16 10.6 8.7 9.8 AM 9.9 9.8 9.6 9.3 9.2 9.0 8.7 8.7 8.7 9.0 9.3 9.6 PM 10.1 10.3 10.6 10.6 10.6 10.6 10.4 10.3 10.3 10.1 10.1 9.910-17 10.9 9.0 10.0 AM 9.8 9.6 9.5 9.3 9.2 9.0 9.0 9.0 9.0 9.2 9.6 9.9

PM 10.3 10.6 10.7 10.9 10.9 10.9 10.9 10.9 10.9 10.9 10.7 10.6

42 Guidelines and Standard Procedures for Continuous Water-Quality Monitors
10-18 11.3 9.5 10.5 AM 10.6 10.3 10.1 9.9 9.8 9.6 9.5 9.5 9.5 9.8 10.1 10.6

PM 10.9 11.2 11.3 11.3 11.3 11.3 11.2 11.0 11.0 10.9 10.7 10.6

10-19 11.2 9.3 10.4 AM 10.6 10.3 10.1 9.9 9.6 9.5 9.3 9.3 9.3 9.6 9.9 10.4

PM 10.7 10.9 11.2 11.2 11.2 11.0 11.0 10.9 10.7 10.7 10.6 10.6

10-20 11.2 9.3 10.4 AM 10.4 10.3 10.1 9.9 9.8 9.6 9.5 9.3 9.3 9.6 9.9 10.4

PM 10.7 11.0 11.2 11.2 11.0 11.0 10.9 10.9 10.7 10.7 10.6 10.4

10-21 11.2 9.3 10.4 AM 10.4 10.3 10.1 9.9 9.6 9.6 9.3 9.3 9.3 9.6 9.9 10.3

PM 10.6 10.9 11.2 11.2 11.2 11.0 11.0 10.9 10.9 10.7 10.6 10.4

10-22 11.3 9.5 10.5 AM 10.4 10.3 10.1 9.9 9.8 9.6 9.5 9.5 9.6 9.8 10.1 10.4

PM 10.9 11.2 11.3 11.3 11.3 11.2 11.2 11.0 11.0 10.9 10.7 10.6

10-23 11.2 9.6 10.6 AM 10.4 10.4 10.3 10.1 9.9 9.8 9.6 9.6 9.6 9.9 10.3 10.6

PM 10.9 11.0 11.2 11.2 11.2 11.2 11.2 11.2 11.2 11.2 11.2 11.0

1 UNITED STATES DEPARTMENT OF INTERIOR - GEOLOGICAL SURVEY - WATER RESOURCES DIVISION STATE 53 DIST 53  PRIMARY COMPUTATIONS OF QUALITY OF WATER DIGITAL MONITOR RECORDS  12471400 DATE PROCESSED: 08-24-2000 @ 11:23 BY kagreene  LIND COULEE WASTEWAY AT SR17 NR WARDEN, WA  (00010) WATER TEMPERATURE STORE STATISTIC(S) 00001, 00002, 00003  PROVISIONAL DATA FOR WATER YEAR ENDING SEPT. 30, 2000 TEST DIFF:****** PUNCH INTERVAL: 60 MIN

VALUES AT INDICATED HOURS

DATE MAX MIN MEAN 1 2 3 4 5 6 7 8 9 10 11 12

Appendixes 43
44 Guidelines and Standard Procedures for Continuous Water-Quality Monitors

Appendix 8—Variable shift corrections
NOOKSACK RIVER BASIN

12212100 FISHTRAP CREEK AT FLYNN ROAD, AT LYNDEN, WA

LOCATION—Lat 48°55'36'', long 122°29'42'', in NW 1/4 SE 1/4 sec.25, T.40 N., R.2 E., Whatcom 

County, Hydrologic Unit 17110004, on left bank, and at mile 1.7.

DRAINAGE AREA—38.1 mi2.

PERIOD OF RECORD—March 1996 to April 1998 (discontinued).

PERIOD OF DAILY RECORD—

SPECIFIC CONDUCTANCE: March to current year.

WATER TEMPERATURE: March to current year.

DISSOLVED OXYGEN: March to September 1996.

INSTRUMENTATION—Water-quality monitor since March 1996. Electronic data logger with 15-

minute recording interval.

REMARKS—Specific conductance records rated excellent except the following periods: Dec. 13–Jan. 

15, Aug. 5–31 rated good; Feb. 15–Mar. 10 rated fair; and Oct. 11–15 rated poor. Temperature records 

rated excellent.

EXTREMES FOR PERIOD OF RECORD—

 SPECIFIC CONDUCTANCE: Maximum recorded, 337 microsiemens Nov. 19, 20, 1996, but may have 

been higher during period of missing record; minimum recorded, 108 microsiemens Jan. 30, 1997, but 

may have been lower during periods of missing record.

 WATER TEMPERATURE: Maximum recorded, 20.5°C July 14, 26, 27, 29, 1996; minimum recorded, 

0.0°C Dec. 26–31, 1996.

 DISSOLVED OXYGEN: Maximum recorded, 12.1 mg/L Mar. 24, 1996, but may have been higher during 

periods of missing record; minimum recorded, 7.1 mg/L July 27, Aug. 26, 1996, but may have been 

lower during periods of missing record.

EXTREMES FOR CURRENT YEAR—

 SPECIFIC CONDUCTANCE: Maximum recorded, 337 microsiemens Nov. 19, 20, but may have been 

higher during period of missing record; minimum recorded, 108 microsiemens. Jan. 30, but may have 

been lower during period of missing record.

 WATER TEMPERATURE: Maximum recorded, 19.0°C Aug. 13, 14, but may have been higher during 

period of missing record; minimum recorded, 0.0°C Dec. 26–31.

Appendix 9—Example of a manuscript station description

Appendixes 45
207-SC

Rev. 8–95 SPECIFIC CONDUCTANCE MEASUREMENT SUMMARY WY 1997

Station Name COLUMBIA RIVER at BEAVER ARMY TERMINAL nr QUINCY, OREGON No.

Copied by: Checked by: Date: 6/11/98

Form 2

Date Time

Stream reading Cleaning and calibration check Datum correction Variable shift

Remarks Recording 

instrument

Portable 

field 

unit

74 STD/

RDNG

147 STD/

RDNG

220 STD/

RDNG

Shift to 

cross 

section

Shift to 

STDS

Aug. 27 10:34 155.7

154/10:00156/10:30

139 91, -17;

161, -14;231, -11

Before cleaning (156) - after cleaning (137) = -19 = cleaning correction

11:01 137

137/11:00136/11:30

139 72 142 212 72, +2;

142, +5;212, +8

12:30 136/12:00

136/12:30

(138*/11:26)

DC = -2 Cross section (136) - used RB 

surface reading of (138*) for reading at probe = -2 = DC

1997 Water Year

Oct. 23 10:20 130

130/10:00NA/10:30

76, -2;146, +1;215, +5

Before cleaning (130) - after cleaning (126) = -4 = cleaning correction

10:55 126

126/11:00125/11:30

131 72 141 + 143 

= 142 = avg

211 72, +2;

142, +5;211, +9

Two different standards were used and results were averaged

12:10 125/12:00

126/12:30126/13:00

(130.5*/11:22)

DC = 0 Cross section (130) - used RB 

surface reading of (130*) for reading at probe = 0 = DC

Appendix 10—Example of an annual field measurement summary form

46 Guidelines and Standard Procedures for Continuous Water-Quality Monitors
Appendixes 47

Appendix 11—Example of a variable shift correction table

VARIABLE SHIFT VALUES

===================================

AGENCY CODE: USGS WATER YEAR: 1999

STATION ID: 12113390

STATION NAME: DUWAMISH R AT GOLF COURSE AT TUKWILA, WA

DATA DESCRIPTION: SPECIFIC CONDUCTANCE FROM EDL, IN US/CM @ 25C

1998 LAST SV: __ __ ____ _______ _______ _______ _______ _______ _______

***2000 FIRST SV: 10 12 1413 49.0 .0 255.0 .0 498.0 .0***

DATE/TIME

MM DD/TTTT

INPUT SHIFT INPUT SHIFT INPUT SHIFT

10 15 1300 52.00 -3.00 255.00 0.00 498.00 0.00

12 15 1135 52.00 -3.00 255.00 0.00 498.00 0.00

01 13 1116 51.00 -2.00 255.00 0.00 498.00 0.00

01 13 1127 52.00 -3.00 255.00 0.00 498.00 0.00

02 12 1116 49.00 0.00 255.00 0.00 498.00 0.00

03 15 1205 49.00 0.00 255.00 0.00 498.00 0.00

04 13 1114 53.00 -4.00 255.00 0.00 498.00 0.00

04 13 1122 55.00 -6.00 255.00 0.00 498.00 0.00

05 12 1305 44.00 5.00 255.00 0.00 498.00 0.00

05 12 1313 49.00 0.00 255.00 0.00 498.00 0.00
48 Guidelines and Standard Procedures for Continuous Water-Quality Monitors Appendix 12—Example of a datum shift correction table DATUM CORRECTION VALUES =================================== AGENCY CODE: USGS WATER YEAR: 1999 STATION ID: 12113390 STATION NAME: DUWAMISH R AT GOLF COURSE AT TUKWILA, WA DATA DESCRIPTION: SPECIFIC CONDUCTANCE FROM EDL, IN US/CM @ 25C 1998 LAST DC: __ __ ____ _______ 2000 FIRST DC: 10 12 1345 -20.0 **************************************************************************** DATE/TIME VALUE DATE/TIME VALUE DATE/TIME VALUE DATE/TIME VALUE MM DD/TTTT MM DD/TTTT MM DD/TTTT MM DD/TTTT 10 12 1300 .0 12 15 1135 .0 01 13 1105 -20.0 01 13 1130 .0 02 12 1112 -15.0

02 12 1115 .003 15 1200 -13.003 15 1215 .004 13 1135 .005 12 1300 -12.005 12 1315 .009 08 1345 .0
Appendixes 49

Appendix 13—Example of an ADAPS daily-values table

UNITED STATES DEPARTMENT OF THE INTERIOR - GEOLOGICAL SURVEY - WASHINGTON STATE NWIS 10/31/2000

STATION NUMBER 12113390 DUWAMISH R AT GOLF COURSE AT TUKWILA, WA STREAM SOURCE AGENCY USGS

LATITUDE 472845 LONGITUDE 1221527 DRAINAGE AREA 461 DATUM STATE 53 COUNTY 033

FROM EDL

SPECIFIC CONDUCTANCE (MICROSIEMENS/CM AT 25 DEG. C), WATER YEAR OCTOBER 1998 TO SEPTEMBER 1999

DAY MAX MIN MEAN MAX MIN MEAN MAX MIN MEAN MAX MIN MEAN

OCTOBER NOVEMBER DECEMBER JANUARY

1 236 180 196 259 141 158 78 63 73 49 41 43

2 289 181 199 244 140 152 78 74 76 44 37 40

3 --- 162 --- 278 141 160 78 75 76 42 38 39

4 325 156 182 280 135 173 75 70 72 49 40 44

5 316 157 184 135 112 124 76 70 74 57 49 53

6 --- 184 --- 248 126 147 76 73 75 63 56 59

7 --- 189 --- 237 142 166 77 74 76 71 58 64

8 --- 192 --- 301 145 173 77 74 75 70 66 68

9 241 171 187 --- 143 --- 84 77 80 74 69 72

10 230 165 178 --- 136 --- 90 81 87 75 72 74

11 286 170 200 --- 131 --- 89 79 85 76 73 74

12 325 184 212 201 125 142 82 75 78 74 63 67

13 189 147 165 143 82 108 75 60 65 64 55 61

14 157 142 149 94 59 79 64 60 62 71 62 64

15 227 149 160 59 56 57 69 59 62 73 65 70

16 223 151 165 58 55 57 64 60 62 84 73 80

17 227 151 172 66 57 62 71 64 68 94 84 90

18 175 147 161 73 64 68 67 61 64 97 94 95

19 177 147 158 77 71 74 72 62 68 103 97 99

20 175 139 158 78 76 77 73 66 69 105 103 104

21 158 126 135 78 76 77 76 66 70 112 105 108

22 156 134 140 76 63 68 93 68 82 113 110 111

23 189 149 167 63 60 61 94 81 86 110 109 110

24 228 150 167 60 58 59 100 79 88 111 110 110

25 228 148 167 59 56 58 91 74 81 113 111 112

26 193 149 162 63 58 61 80 74 76 119 113 115

27 285 150 177 61 59 60 79 64 72 124 119 121

28 163 130 144 60 56 57 64 55 60 126 120 124

29 227 147 167 59 57 58 55 45 47 120 114 117

30 266 145 165 64 58 60 48 44 47 115 114 115

31 328 143 171 --- --- --- 45 43 44 118 115 117

MONTH --- 126 --- --- 55 --- 100 43 71 126 37 85
50 Guidelines and Standard Procedures for Continuous Water-Quality Monitors

DAY MAX MIN MEAN MAX MIN MEAN MAX MIN MEAN MAX MIN MEAN

FEBRUARY MARCH APRIL MAY

1 118 117 118 77 73 75 125 107 116 115 90 101

2 118 116 117 85 75 80 137 114 125 97 88 92

3 116 112 113 85 83 84 132 110 119 93 79 85

4 112 104 107 84 82 82 123 110 116 80 74 76

5 104 103 104 88 82 85 123 111 116 85 75 79

6 109 104 107 99 87 94 133 111 120 96 80 86

7 111 109 111 104 99 101 135 115 125 96 85 91

8 112 111 111 108 103 106 132 115 122 88 75 80

9 113 112 113 109 105 107 129 113 119 87 74 78

10 117 113 115 118 107 113 131 112 121 93 81 87

11 118 116 117 124 117 121 131 111 120 90 81 85

12 121 112 118 128 121 125 133 111 119 99 77 85

13 122 112 116 124 112 115 130 106 112 99 74 80

14 118 108 113 113 105 108 130 104 112 95 73 81

15 131 109 120 112 105 107 133 105 113 102 76 83

16 132 116 123 112 91 102 132 92 106 103 77 86

17 123 112 117 106 94 101 116 81 92 102 78 91

18 120 111 116 110 97 104 103 80 87 90 81 84

19 113 100 105 129 100 115 87 65 75 90 71 78

20 113 104 109 131 112 121 82 63 72 79 63 69

21 116 106 112 123 102 113 80 71 75 77 63 69

22 118 105 113 112 93 101 83 71 75 75 61 66

23 110 102 104 102 64 75 90 75 81 73 60 63

24 103 76 83 76 64 70 93 81 85 74 61 64

25 96 81 90 77 69 73 95 82 88 75 62 65

26 101 95 98 77 69 74 90 70 77 72 62 65

27 101 77 85 84 69 77 75 69 71 73 60 63

28 80 74 77 89 76 85 74 68 71 69 58 61

29 --- --- --- 93 83 88 86 68 76 74 58 62

30 --- --- --- 107 93 99 110 80 96 74 61 64

31 --- --- --- 114 99 107 --- --- --- 76 61 65

MONTH 132 74 108 131 64 97 137 63 100 115 58 77

UNITED STATES DEPARTMENT OF THE INTERIOR - GEOLOGICAL SURVEY - WASHINGTON STATE NWIS 10/31/2000

STATION NUMBER 12113390 DUWAMISH R AT GOLF COURSE AT TUKWILA, WA STREAM SOURCE AGENCY USGS

LATITUDE 472845 LONGITUDE 1221527 DRAINAGE AREA 461 DATUM STATE 53 COUNTY 033

FROM EDL

SPECIFIC CONDUCTANCE (MICROSIEMENS/CM AT 25 DEG. C), WATER YEAR OCTOBER 1998 TO SEPTEMBER 1999

Appendix 13—Example of an ADAPS daily-values table (Continued)
Appendixes 51

DAY MAX MIN MEAN MAX MIN MEAN MAX MIN MEAN MAX MIN MEAN

JUNE JULY AUGUST SEPTEMBER

1 76 62 66 135 86 104 230 156 174 254 151 174

2 75 61 64 139 101 112 239 150 168 264 154 178

3 82 62 68 124 94 102 263 149 203 264 161 180

4 103 67 83 106 79 89 263 151 172 272 163 193

5 101 80 87 98 77 82 193 144 170 276 162 187

6 99 77 82 98 76 81 193 133 155 268 160 189

7 102 75 80 111 77 86 167 127 142 248 160 180

8 95 60 70 113 80 87 159 119 132 386 159 199

9 79 60 64 146 80 104 190 125 149 306 161 193

10 92 61 73 151 107 123 192 130 145 260 161 189

11 103 71 79 147 105 113 233 140 171 256 160 190

12 100 67 75 156 105 111 248 151 175 240 161 182

13 89 66 70 143 102 111 241 151 168 222 160 176

14 91 66 71 147 99 111 232 149 174 171 157 162

15 94 66 71 148 95 105 199 145 164 167 157 162

16 93 55 64 144 95 114 202 148 175 170 154 160

17 81 55 59 112 81 91 215 148 168 178 146 163

18 88 58 65 113 83 92 220 144 161 171 144 159

19 116 61 82 129 91 101 250 150 170 162 143 152

20 116 86 91 146 93 105 244 151 169 157 133 146

21 114 82 94 147 97 107 263 156 193 159 131 145

22 114 87 98 138 91 102 253 160 181 131 105 122

23 123 91 103 145 91 105 273 162 195 108 103 105

24 112 72 85 153 97 110 260 162 182 363 99 133

25 81 66 72 150 96 110 251 162 178 163 107 123

26 93 67 77 169 96 124 268 160 184 191 106 129

27 99 76 82 219 122 160 235 158 176 175 110 118

28 103 77 85 238 168 188 250 158 177 172 110 125

29 103 77 83 249 165 192 258 161 183 207 112 135

30 117 79 92 244 167 193 266 159 186 163 116 134

31 --- --- --- 254 159 184 230 153 170 --- --- ---

MONTH 123 55 78 254 76 116 273 119 171 386 99 159

UNITED STATES DEPARTMENT OF THE INTERIOR - GEOLOGICAL SURVEY - WASHINGTON STATE NWIS 10/31/2000

STATION NUMBER 12113390 DUWAMISH R AT GOLF COURSE AT TUKWILA, WA STREAM SOURCE AGENCY USGS

LATITUDE 472845 LONGITUDE 1221527 DRAINAGE AREA 461 DATUM STATE 53 COUNTY 033

FROM EDL

SPECIFIC CONDUCTANCE (MICROSIEMENS/CM AT 25 DEG. C), WATER YEAR OCTOBER 1998 TO SEPTEMBER 1999

Appendix 13—Example of an ADAPS daily-values table (Continued)
52 Guidelines and Standard Procedures for Continuous Water-Quality Monitors

Appendix 14—Example of a discharge hydrograph
Appendix 15—Example of a review graph for an individual water-quality 

property

Appendixes 53

400

300

200

100

SPECIFIC CONDUCTANCE, IN MICROSIEMENS PER CENTIMETER AT 25 DEGREES CELSIUS

0

OCT. NOV. DEC. JAN. FEB. MAR. APR. MAY

1997 1998

JUNE JULY AUG. SEPT.