U.S. Department of the Interior

U.S. Geological Survey

Data-Collection Methods, Quality-Assurance Data, 

Site Considerations for Total Dissolved Gas Monitor

Lower Columbia River, Oregon and Washington, 200

Water-Resources Investigations Report 01–4005

Prepared in cooperation with the

U.S. ARMY CORPS OF ENGINEERS
Cover Photograph. Columbia River at John Day Dam, April 2000. (Photograph by Amy Brooks, U.S. Geological Surv
U.S. Department of the Interior

U.S. Geological Survey

Data-Collection Methods, Quality-Assurance Data

Site Considerations for Total Dissolved Gas Monito

Lower Columbia River, Oregon and Washington, 2

By DWIGHT Q. TANNER AND MATTHEW W. JOHNSTON

Water-Resources Investigations Report 01–4005

Prepared in cooperation with the

U.S. ARMY CORPS OF ENGINEERS

Portland, Oregon: 2001
II

U.S. DEPARTMENT OF THE INTERIOR

BRUCE BABBITT, Secretary

U.S. GEOLOGICAL SURVEY

Charles G. Groat, Director

The use of trade, product, or firm names in this publication is for

descriptive purposes only and does not imply endorsement by the

U.S. Government.

For additional information contact: Copies of this report can 

purchased from:

District Chief

U.S. Geological Survey USGS Information Servic

10615 S.E. Cherry Blossom Drive Box 25286, Federal Cente

Portland, OR 97216-3159 Denver, CO 80225-0046

E-mail: info-or@usgs.gov Telephone: 1-888-ASK-US

Internet: http://oregon.usgs.gov

Suggested citation:

Tanner, D.Q., and Johnston, M.W., 2001, Data-collection methods, quality-assurance data, and site

considerations for total dissolved gas monitoring, lower Columbia River, Oregon and Washington, 200

U.S. Geological Survey Water-Resources Investigations Report 01–4005, 19 p.
III

CONTENTS

Abstract.................................................................................................................................................................................. 

Introduction ........................................................................................................................................................................... 

Background.................................................................................................................................................................. 

Purpose and Scope....................................................................................................................................................... 

Acknowledgments ....................................................................................................................................................... 

Methods of Data Collection................................................................................................................................................... 

Instrumentation............................................................................................................................................................ 

Calibration of Instruments in the Laboratory .............................................................................................................. 

Calibration of Instruments in the Field........................................................................................................................ 

Daily Quality-Assurance Checks.................................................................................................................................

Data Workup and Archive ...........................................................................................................................................

Summary of Data Completeness and Quality........................................................................................................................

Quality-Assurance Data.........................................................................................................................................................

Site-Specific Considerations..................................................................................................................................................

Camas ..........................................................................................................................................................................

Skamania .....................................................................................................................................................................

Warrendale...................................................................................................................................................................

Bonneville....................................................................................................................................................................

The Dalles Tailwater....................................................................................................................................................

The Dalles Forebay......................................................................................................................................................

John Day Tailwater ......................................................................................................................................................

John Day Forebay........................................................................................................................................................

References Cited....................................................................................................................................................................

FIGURES

1. Total dissolved gas fixed stations, lower Columbia River, Oregon and Washington, water year 2000.......................... 

2. Example of a laboratory calibration form ........................................................................................................................ 

3. Graph showing the accuracy of total dissolved gas sensors when compared to a primary standard after

field deployment .............................................................................................................................................................. 

4. Example of a field inspection/calibration sheet ............................................................................................................... 

5. Graphs showing the difference between the secondary standard and the field barometers .............................................

6. Graphs showing the difference between the secondary standard and the field thermometers .........................................

7. Graphs showing the total dissolved gas difference between the field probe and lab probe initially................................

8. Graphs showing the total dissolved gas difference between the field probe and lab probe at the end of

field calibrations ..............................................................................................................................................................

9. Example of the checklist for total dissolved gas daily quality-assurance checks ............................................................

10. Graph showing total dissolved pressure above and below John Day Dam .....................................................................

11. Example of a data table from U.S. Army Corps of Engineers Total Dissolved Gas Reports Web page.........................

12. Graph showing selected total dissolved gas data at the main and duplicate probes at John Day tailwater.....................

13. Graph showing all of the total dissolved gas data at the main and duplicate probes at John Day tailwater....................

14. Graph showing duplicate water temperature data at John Day forebay and water temperature data at

John Day tailwater...........................................................................................................................................................

15. Graph showing duplicate total dissolved gas data at John Day forebay..........................................................................

16. Graph showing compensation depth and actual probe depth at Warrendale ...................................................................

TABLES

1. Total dissolved gas fixed stations, lower Columbia River, Oregon and Washington, water year 2000 ........................... 

2. Total dissolved gas data completeness and quality, water year 2000 ................................................................................
1

Data-Collection Methods, Quality-Assurance Data, 

Site Considerations for Total Dissolved Gas Monito

Lower Columbia River, Oregon and Washington, 200

By Dwight Q. Tanner and Matthew W. Johnston

ABSTRACT

Excessive total dissolved gas pressure can

cause gas-bubble trauma in fish downstream from

dams on the Columbia River. In cooperation with

the U.S. Army Corps of Engineers, the U.S. Geological Survey collected data on total dissolved gas

pressure, barometric pressure, water temperature,

and probe depth at eight stations on the lower

Columbia River from the John Day forebay (river

mile 215.6) to Camas (river mile 121.7) in water

year 2000 (October 1, 1999, to September 30,

2000). These data are in the databases of the

U.S. Geological Survey and the U.S. Army Corps

of Engineers. Methods of data collection, review,

and processing, and quality-assurance data are

presented in this report.

INTRODUCTION

The U.S. Army Corps of Engineers (USACE)

operates several dams in the Columbia River Basin,

which encompasses 259,000 square miles of the Pacific

Northwest. These dams are multipurpose facilities that

fill regional needs for flood control, navigation, irrigation, recreation, hydropower production, fish and wildlife habitat, water-quality maintenance, and municipal

and industrial water supply. When water is released over

the spillways of these dams, air is entrained in the water,

sometimes increasing the concentration of total dissolved gas (TDG) downstream from the spillways in

excess of the U.S. Environmental Protection Agency’s

water-quality criterion of 110-percent saturation for the

protection of freshwater aquatic life. Concentrati

above this criterion have been shown to cause ga

ble trauma in fish and adversely affect other aqua

organisms (U.S. Environmental Protection Agen

1986). USACE minimizes spill and regulated str

flow in the region to minimize the production of e

TDG downstream from its dams. USACE collect

time TDG data (data available within about 4 hou

current time) upstream and downstream from the 

in a network of fixed-station monitors.

Background

Real-time TDG data are vital to USACE fo

operation and for monitoring compliance with en

mental regulations. The data are used by water m

ers to maintain water-quality conditions that faci

fish passage and survival in the lower Columbia 

The U.S. Geological Survey (USGS), in coopera

with the Portland District of USACE, has collect

TDG and related data in the lower Columbia Riv

every year beginning in 1996. A report was publis

1996 that contained a description of the methods o

collection, the quality-assurance program, and su

ries of data (Tanner and others, 1996).

 Data-collection methods and quality-assur

plans have changed significantly since 1996. In w

year 2000, new TDG/temperature probes and new

methods of calibration in the laboratory and in th

were used.

To provide a suitable data set for water man

to model TDG in the lower Columbia River, the 

time hourly data for water year 2000 were correc

deleted to reflect measurements made during instr
2

calibration. The reviewed and corrected hourly data are

stored in a USGS data base (Automated Data Processing System—ADAPS) and in a USACE data base at

http://www.nwd-wc.usace.army.mil/TMT/tdg_data.

Purpose and Scope

The purpose of TDG monitoring is to provide

USACE with (1) real-time data for managing streamflows and TDG levels upstream and downstream from

its project dams in the lower Columbia River and (2)

reviewed and corrected TDG data to evaluate conditions

in relation to water-quality criteria and to develop a

TDG data base for modeling the effect of various management scenarios of streamflow and spill on TDG

levels.

This report describes the data-collection techniques and quality-assurance data for the TDG monitoring program on the Columbia River from the forebay of

the John Day dam (river mile [RM] 215.6) to Camas

(RM 121.7). Data for water year 2000 included total

dissolved gas pressure, barometric pressure, and watertemperature at eight fixed stations on the lower Columbia River (fig. 1, table 1).

Acknowledgments

We wish to acknowledge the aid and fundin

port of the U.S. Army Corps of Engineers. Our sp

thanks to James L. Britton (USACE) for technica

logistical support of the project. The authors also

acknowledge Amy Brooks and Tirian Mink (USG

for assistance in data collection and for preparing

summaries of data. Howard E. Harrison, formerly 

USGS, helped develop several of the data-collecti

and quality-assurance protocols.

METHODS OF DATA COLLECTION

Instrumentation

Instrumentation at each fixed station consist

a TDG probe, an electronic barometer, a data-colle

platform (DCP), and a power supply. The TDG pr

was manufactured by Hydrolab Corporation. The p

had individual sensors for TDG, temperature, and 

depth (unvented sensor). The TDG sensor consist

a cylindrical framework wound with a length of Si

3

5 8 2 1 4 7

6

EXPLANATION

Monitoring site

8 Map reference number

(see Table 1)

Deschutes 

Willamette

River

River

River

River

Lewis

Cowlitz

River

John Da

Portland y

123° 121°

45°

46°

John Day

Dam

The Dalles

Dam Bonneville

Dam

Study

area

Washington

Oregon

P A

C IFI

C

O

C EAN

C O L UMB I A

R I V E R

Figure 1. Total dissolved gas fixed stations, lower Columbia River, Oregon and Washington, water year 2000.
3

 Table 1. Total dissolved gas fixed stations, lower Columbia River, Oregon and Washington, water year 2000[Map reference number refers to figure 1; USACE, U.S. Army Corps of Engineers; Columbia River mile locations were determined from U.S. Geological Survey (USstations are referenced by their abbreviated name in this report]

Map

reference

number

USACE

site

identifier

Columbia

River mile

USGS

station number

USGS station name

(abbreviated station name) Latitude Longitude 

1 JDA 215.6 454257120413000 Columbia River at John Day Dam forebay, Washington

(John Day forebay)

45 ̊ 42’ 57” 120 ̊ 41’ 30

2 JHAW 214.7 454249120423500 Columbia River, right bank, near Cliffs, Washington

(John Day tailwater)

45 ̊ 42’ 49” 120 ̊ 42’ 35

3 TDA 192.6 453712121071200 Columbia River at The Dalles Dam forebay, Washington

(The Dalles forebay)

45 ̊ 37’ 12” 121 ̊ 07’ 12

4 TDDO 188.9 14105700 Columbia River at The Dalles, Oregon

(The Dalles downstream)

45 ̊ 36’ 27” 121 ̊ 10’ 20

5 BON 146.1 453845121562000 Columbia River at Bonneville Dam forebay, Washington

(Bonneville forebay)

45 ̊ 38’ 45” 121 ̊ 56’ 20

6 SKAW 140.5 453651122022200 Columbia River, right bank, near Skamania, Washington

(Skamania)

45 ̊ 36’ 51” 122 ̊ 02’ 22

7 WRNO 140.4 453630122021400 Columbia River, left bank, near Dodson, Oregon

(Warrendale)

45 ̊ 36’ 30” 122 ̊ 02’ 14

8 CWMW 121.7 453439122223900 Columbia River, right bank, at Washougal, Washington

(Camas)

45 ̊ 34’ 39” 122 ̊ 22’ 39
4

(dimethyl silicon) tubing. The tubing was tied off at one

end and the other end was connected to a pressure transducer. After the TDG pressure in the river equilibrated

with the gas pressure inside the tubing (about 15 to 20

minutes), the pressure transducer produced a measure

of the TDG pressure in the river. The water-temperature

sensor was a thermocouple. The barometer was contained in the display unit of the Model TBO-L, a total

dissolved gas meter manufactured by Common Sensing, Inc.

The TDG probe was connected by a heavy-duty,

weatherproof cable to a Sutron Model 8200 DCP. The

DCP had three basic functions: sensor interfacing, data

storage, and data transmission to the Geostationary

Operational Environmental Satellite (GOES) system

(Jones and others, 1991). A crossed Yagi antenna was

connected to the DCP using a coaxial cable. The

antenna was mounted on a mast to provide transmission

to the GOES system.

The barometer, TDG probe, and the DCP were

powered by a 12-volt gelled-electrolyte battery. The

battery was charged by a regulated-voltage circuit from

a solar panel and/or a 120-volt alternating-current line.

The DCP was programmed to record and transmit

five parameters: barometric pressure (in millimeters of

mercury), TDG pressure (in millimeters of mercury),

probe depth (in feet), water temperature (in degrees

Celsius), and battery voltage (in volts). Battery-voltage

data were monitored to determine whether the instrumentation was receiving adequate power. The data for

each parameter were logged electronically every hour,

on the hour, and stored in the DCP memory. Every 4

hours, the DCP transmitted the most recent 12 hours of

logged data to the GOES satellite. Consequently, each

piece of data was transmitted three times to protect

against data loss. The GOES satellite retransmitted the

data to a direct readout ground station, where the data

were automatically decoded and transferred to the

USACE data base (Columbia River Operation

Hydromet Management System—CHROMS), and to

the USGS ADAPS data base. During the fixed-station

calibration visits, the DCP-stored data were downloaded to a palmtop computer. When it was necessary to

fill in any real-time data lost during satellite transmission, these data were supplied to USACE and also

loaded into the database at the USGS office in Portland,

Oregon.

At one site, John Day tailwater, two TDG probes

were installed inside the same probe housing, which

was perforated at the end and extended into the flow of

the Columbia River. The primary probe was at the 

end of the plastic pipe and the secondary probe w

located about 1 foot (measured vertically) above 

first. This was done for the following reasons: 

ensure that data were reliably collected at this imp

site and (2) to provide an assessment of the varia

of the TDG measurement.

Calibration of Instruments in the Laboratory

The fixed station monitors were calibrated 

2 weeks from March 10 to September 15, 2000, 

every 3 weeks for the remainder of the year, at w

time Warrendale and Bonneville forebay were th

sites in operation. The general procedure was to 

the operation of the TDG probe in the field witho

turbing it, replace the field probe with one that ha

been calibrated in the laboratory, and then check 

operation of the newly deployed field probe. The d

of the laboratory calibration procedure follow.

Each time a TDG probe was removed from 

2- or 3-week deployment in the river, it was calib

in the Oregon District laboratory before being re

ployed. First, the TDG value in millimeters of me

was measured in ambient conditions with the TD

membrane still attached to the sensor and compa

the ambient barometric pressure as measured by a 

held aneroid barometer (fig. 2, item 1). (The aner

barometer was calibrated every 2 weeks at the Na

Weather Service facility in Portland, Oregon.) If 

measurement by the TDG probe and the measure

by the aneroid barometer were approximately eq

this check was considered acceptable.

Pressure calibrations were done using a Ne

DigiMano 2000 digital pressure gage, which was 

fied according to standards of the National Institu

Standards and Technology (NIST). The end of the 

probe containing the sensors was put in a plastic 

sure chamber and the pressure was increased 200 

Hg (millimeters of mercury) above the ambient b

metric pressure (fig. 2, item 2). The pressure mea

by the TDG sensor should increase gradually, un

reaches a level approximately 200 mm Hg above 

metric pressure, within about 10 minutes. This w

indicate that the pressurized air was penetrating t

membrane at a gradual rate. On occasions when 

was an opening torn in the membrane, the pressur

sured by the TDG sensor would increase rapidly, 

cating that the membrane should be replaced.
5

Figure 2. Laboratory calibration form.

 HYDROLAB LABORATORY PROCEDURES

To be done when a Hydrolab is brought in from a 2 or 3-week deployment.

Hyrolab #______________ Lab barometer ID ___________

TDG sensor #___________ Date baro last calib. ___________

Site Hyd. was deployed _______Today's date ___________

Date removed _________ Checked by ___________

1. TEST LOW CALIBRATION WITH MEMBRANE ATTACHED.

Lab BP _________ mm Hydrolab Pt ________ mm Time _______

2. TEST HYDROLAB WITH DIGITAL PRESSURE GAGE AND PRESSURE CHAMBER.

Lab BP + 200mm = ______ mm

Before applying 200 mm pressureHydrolab Pt ________ mm Time _______

After applying pressure Hydrolab Pt ________ mm Time _______

3. TEST HYDROLAB WITH CLUB SODA.

Before soda test Hydrolab Pt ________ mm Time _______

High pressure, soda test Hydrolab Pt ________ mm Time _______

Low pressure, after soda test Hydrolab Pt ________ mm Time _______

(If the Hyd. does not perform well on #1 - #3 above, re-evaluate the correspondin

site record.)

Remove TDG membrane, clean the membrane, air dry, store in dessicator.

Allow TDG sensor to air dry for at least 24 hours.

Then test Hydrolab before redeployment, below.

_______________________________________________________________________________________

1. CALIBRATE TDG WITH DIGITAL PRESSURE GAGUE.

Date __________ Lab BP ________ mm

Time __________ Hydrolab Pt ________ mm

 ________ ________

Baro+100mm expected/meas.

 ________ ________

Baro+200mm expected/meas.

 ________ ________

Baro+300mm expected/meas.

If any readings are >2 mm off, do a 2-point calibration at barometric pressure

and barometric pressure + 200 mm and note below.

2. INSTALL DRY MEMBRANE AND INSTALL THE SENSOR GUARD.

3. TEST HYDROLAB WITH CLUB SODA.

Before soda test Hydrolab Pt ________ mm Time _______

High pressure, soda test Hydrolab Pt ________ mm Time _______

Low pressure, after soda test Hydrolab Pt ________ mm Time _______

4. CLEAN AND DRY THE HYDROLAB.

5. CHECK MEMBRANE FOR INTERNAL MOISTURE AFTER THE OUTSIDE OF THE MEMB. HAS HAD TIME TO 

Label as ready for field deployment, with date. Completed Date ________ Time ________

37603

63369

SKAW

6/5/00

5/18/00

6/13/00

dqt

TM

765 762

965

1403

762

762

862 860

962 961

1062

771 0907

1002 0908

746 0909

1061

760

1403

760 1519

1011 1520

728 1522

964 1412

1415

6/14/00

6/15/00 baro=767

6/16/00 1400
6

Subsequently, the TDG membrane / TDG sensor

units were tested for responsiveness to supersaturation

by inserting the probe into a container filled with supersaturated carbonated water (club soda). If the membrane/sensor was operating correctly, the measured

TDG rose to at least 1,000 mm Hg in 2 to 3 minutes

(fig. 2, item 3). If the response was not this large, the

membrane was replaced.

Next, the TDG membrane was cleaned with a

squirt bottle of tap water, then removed from the sensor.

The TDG membrane was dried in a desiccator for at

least 24 hours, and, at the same time, the TDG sensor

was air dried at room temperature. This step was important because water sometimes collected inside the tubular membrane due to condensation. If the condensation

is not removed, it can slow the equilibration of air pressure between the outside of the membrane and the TDG

sensor.

After the TDG membrane and sensor had been

dried, the TDG sensor, with the membrane still unattached, was tested at ambient pressure conditions (i.e.

barometric pressure, as measured by the aneroid barometer) and at added pressures of 100 mm Hg, 200 mm Hg,

and 300 mm Hg measured by the pressure gage, which

was the primary standard (lower half of fig. 2, item 1).

For example, using the barometric pressure of 760 mm

Hg, the added pressures of 0, 100, 200, and 300 mm Hg

correspond to TDG percent saturations of 100%,

113.2%, 126.3%, and 139.5%, respectively. The results

of these calibrations for water year 2000 are shown in

figure 3. Almost all of the calibrations were within

1-percent saturation of total dissolved gas. One outlier,

for 0 mm Hg added pressure at Skamania, was 5.3 percent larger than expected. This result indicated that the

sensor was defective, and it was replaced.

If any of the measurements differed more than

3 mm Hg from the primary standard, the sensor was calibrated at two points, barometric pressure and barometric pressure plus 200 mm Hg. Then the calibration of the

TDG sensor was checked a second time according

to the procedure above to be sure that it was correctly

calibrated at the various pressures.

After the pressure check and calibration (if

needed) of the TDG sensor, the dried membrane was

reattached to the sensor, and the sensor guard was

screwed back on the probe. Then another test was done

for responsiveness to supersaturation with “club soda”

(carbonated water) (lower half of fig. 2, item 3). Again,

if the membrane/sensor was operating correctly, the

measured TDG rose to at least 1,000 mm Hg in 2 or 3

minutes. If the response was not this large, the m

brane was replaced. This second test, with club s

was done because the process of installing the se

guard had been found to abrade the TDG membra

the test ensured that the membrane was still funct

The final step was to inspect the inside of t

membrane for moisture (lower half of fig. 2, item 

no moisture was visible, the TDG probe was labe

ready for field deployment.

In addition to the TDG probes that were ca

brated for replacement in the field each 2 to 3 we

ibration interval, one TDG probe was calibrated e

to 3 weeks for use in the field as a secondary stan

This was the probe designated “Lab” on figure 3

TDG sensor was calibrated in the manner describ

above, and, additionally, the temperature calibrat

was checked in a water bath at a temperature near 

ambient river temperature at the time. The tempe

displayed for the probe thermistor was compared 

temperature as read to the nearest 0.1 degrees Ce

with a NIST-traceable mercury thermometer. The 

temperature probe for the “Lab” Hydrolab could 

adjusted to display the correct temperature, so th

needed adjustment (if any) was recorded for later 

during the field calibrations.

Calibration of Instruments in the Field

The fixed station monitors were calibrated 

2 weeks from March 10 to September 15, 2000, 

every 3 weeks for the remainder of the year, at w

time Warrendale and Bonneville forebay were th

sites in operation. The general procedure was to 

the operation of the field probe without disturbin

then replace the field probe with one that had bee

recently calibrated in the laboratory (as described

above) and check the operation of the newly dep

field probe. The details of the field procedure fol

The first step was to fill out the heading of 

field sheet (fig. 4) indicating site, date and time, w

conditions, and identification of the equipment a

site. Then the “LAB” TDG probe (the secondary 

dard) was placed in the river at a location adjacent 

field probe (fig. 4, item 1). The instrument shelte

waterproof metal enclosure) was checked to ensu

the vent was unobstructed so that the barometer c

effectively measure the ambient barometric press

(fig. 4, item 2).

A palmtop computer was connected to the 

allowing for data retrieval and program adjustme
7

-2

2

-1

0

1

-2

2

-1

0

1

-2

2

-1

0

1

-2

2

-1

0

1

TOTAL DISSOLVED GAS, IN PERCENT SATURATION

0 100 200 300

-2

2

-1

0

1

THE DALLES TAILWATER

N=13

THE DALLES FOREBAY

N=14

JOHN DAY FOREBAY

N=14

JOHN DAY TAILWATER 

PRIMARY PROBE; N=14

JOHN DAY TAILWATER 

SECONDARY PROBE; N=13

-2

2

-1

0

1

-2

2

-1

0

1

-2

2

-1

0

1

EXPLANATION

10th percentile

25th percentile

Median

75th percentile

90th percentile

Data values ou

 the 10th and 

 percentiles

-2

2

-1

0

1

0 100 200 300

APPLIED PRESSURE, IN MILLIMETERS OF MERCURY OVER BAROMETRIC PRESSURE

-2

2

-1

0

1

LAB

N=16

CAMAS

N=16

BONNEVILLE FOREBAY

N=18

SKAMANIA

N=13

WARRENDALE

N=22

5.3

Figure 3. Accuracy of total dissolved gas sensors when compared to a primary standard after field deployment.

(Total dissolved gas value from primary standard minus value from field total dissolved gas probe.)
8

P

------------------------------------------------------------------

HYDROLAB TDG FIELD INSPECTION/CALIBRATION SHEET (1/00 version)

----- USGS Portland, Oregon (503)251-3200 ----------------------

Site ID: ___________ Date: ___________ Arrive time:__________

Personnel: _____________________ Purpose: ______________________

Weather: ______________________________ Air temperature: ______ C

Observed spill conditions: ______________________________________

DCP#____________ TBO#_____

Lab Hydrolab #_______________________ Date last cal._____________

Lab Barometer ID _______________________ Date last cal.__________

1. WITHOUT MOVING THE OLD FIELD HYDROLAB, PLACE LAB HYDROLAB

 IN RIVER AT DEPTH OF OLD FIELD HYDROLAB Time: ________

2. IS SHELTER VENT OBSTRUCTED (Y/N): ____

3. CONNECT COMPUTER AND CHECK DCP

Dump logged data to file: ________________.LOG (_____kb)

 Most recent logged data: time_____ baro_____ temp____ depth____ Pt_____

 DCP clock time: ______________ GMT time (watch): _____________

 Reset clock (Y/N): ____

 Recording status (check one): ___ ON&TX, ___ ON&FT, ___ ON, ___ OFF

 Antenna angle approx. 35-40 degrees to horizon (Y/N): _____

 Antenna direction approx. 180 degrees - south (Y/N): _____

 Battery minimum: _______ VDC Battery maximum: _______ VDC

 Next transmission: ______ GMT Error messages (Y/N): ___ (log in notes)

 Clear status (Y/N): ____

4. CHECK POWER AND CHARGING SYSTEM WITH MULTI-METER

 AC (at outlet): ______ VAC

DISCONNECT battery IF next transmission NOT imminent

 BATTERY (at poles): ______ VDC

 REGULATOR (at leads to battery from DCP = 13.8VDC/.75A): ______ VDC

RECONNECT battery, then disconnect right side DCP bus bar

 SOLAR PANEL OR AC/DC CONVERTOR (at PWR IN screws): ______ VDC

RECONNECT bus bar

5. BAROMETRIC PRESSURE

 _____________ mm - ___________ mm = __________ mm IF |*5*| > 10mm, replace TBO

 Lab BP TBO BP *5*

 _____________ mm - ___________ mm = __________ mm

 Lab BP DCP BP Back Shift

 Reset DCP Old offset ______ New offset _______ Time: ________

6. TEMPERATURE Uncorrected Lab WT = __________ C

 ________________ C - ____________ C = _____________ C Time: ________

 Corrected Lab WT Old Field Hyd WT Back Shift

NOTES: _________________________________________________________________________________________

________________________________________________________________________________________________

________________________________________________________________________________________________

________________________________________________________________________________________________

________________________________________________________________________________________________

________________________________________________________________________________________________

________________________________________________________________________________________________

5-24-00 1020

1025

1700 17:33:30

18:11:10

17:33:29

763

763 760

763 764

14.64 17.46 836

BON

Brooks

sunny

37409

33674

DQT

5-18-00

5-18-00

19 All gates

20.8

calibration

N

N

N X

Y

Y

120.0

13.33

13.29

13.76

Y

5/12/2000

13.26 13.34

3

3

0.001

-1

0 1037

1038

14.61

14.71 14.67 +.04

Figure 4. Field inspection/calibration sheet.
9

Page 

 7. AFTER A MIN. OF 15 MIN. IF LAB & OLD FIELD HYD PT READINGS HAVE NOT CHANGED 1 MM./2 MIN. AFTER

 SHAKING LAB HYDROLAB OR IF LAB & OLD FIELD HYD ARE CHANGING BUT DIFFERENCE IS CONSTANT:

 ___________ mm - ____________ mm = _____________ mm Time: ________

 Lab Hyd PT Old Field Hyd PT Back Shift Ol

 Time Lab Pt Fld Pt

8. CALCULATE MINIMUM SENSOR COMPENSATION DEPTH (MSCD) | |

 (Lab PT - Lab BP) / 23 = _________ ft. | |

 Sensor depth at arrival: _________ ft. | |

9. IF OLD FIELD HYD NOT AT OR BELOW MSCD, LOWER OLD FIELD AND LAB HYD TO MSCD.

 ALLOW TO STABILIZE AND RECORD OLD LAB AND FIELD PT AND WT IN NOTES.

10. REMOVE OLD FIELD HYDROLAB FROM RIVER Record Old Fld. Hydrolab # ____________ Time: _______

11. CHECK DEPTH PARAMETER ON OLD FIELD HYDROLAB

Depth reading (Hydrolab out of the river) _____ ft Time: ________

12. CONNECT NEW FIELD HYDROLAB, CALIBRATE DEPTH PARAMETER, CHECK Pt IN AIR

 New Field Hydrolab # ________________ Last caibrated _______________

 Depth reading before zeroing ______ ft Reset depth to 0.0 ft

 Record Pt reading in ambient air ______ mm Time: ________

13. DEPLOY NEW FIELD HYDROLAB IN RIVER AT 15' OR MAXIMUM DEPTH OF SENSOR HOUSING

 Sensor depth: _____ ft Time: ________

14. TEMPERATURE Uncorrected Lab WT = _______ C

 ________________ C - ____________ C = _______ C

 Corrected Lab WT New Field Hyd WT

 Reset DCP Old offset ______ New offset _______ Time: ________

15. AFTER A MIN. OF 15 MIN. IF LAB & NEW FIELD HYD PT READINGS HAVE NOT CHANGED 1 MM./2 MIN. AFTER

 SHAKING NEW FIELD HYDROLAB OR IF LAB & NEW FIELD HYD ARE CHANGING BUT DIFFERENCE IS CONSTANT:

 New

 Time Lab Pt Fld Pt

 ___________ mm - ____________ mm = ___________ mm Time: ________ | |

 Lab Hyd PT New Field Hyd PT *15* | |

| |

 IF |*15*| is > 10 mm, replace new Hydrolab with a backup, or do A and B

A. TEST NEW FIELD AND LAB HYD. WITH CLUB SODA:

 New Fld. Hyd. ___________ mm Time: ________

 Lab Hyd. ___________ mm Time: ________

B. TEST NEW FIELD AND LAB HYD. WITH PRESSURE GAGE AND CHAMBER:

 New Fld. Hyd. ambient___________ mm; plus 200mm__________ mm Time: ________

 Lab Hyd. ambient___________ mm; plus 200mm__________ mm Time: ________

IF NEW FLD. HYDROLAB FAILS EITHER TEST, REPLACE IT WITH A BACKUP HYDROLAB.

IF LAB HYDROLAB FAILS EITHER TEST, USE A BACKUP HYDROLAB TEMPORARILY AS THE LAB METER.

16. CHECK DCP OFFSET FOR Pt = ZERO Y/N: _____

17. SAVE SETUP, CHECK RECORDING STATUS = "ON&TX", DISCONNECT LAPTOP Y/N: _____

Equipment changed other than Hydrolab (Y/N, item): ___,_____________ End time: ________

NOTES: ____________________________________________________________________________________________

___________________________________________________________________________________________________

___________________________________________________________________________________________________

855

868

860

857

856

853

836

851

852

853

853

855-763=92/23

853

33768

37599 -0.13

1055

1056

1057

1103

1104

1122

853

852

855

856

1106

1124

1126

761

16.32

14.62

14.72 14.66

-0.07

2 1054

1039

1045

1047

1049

1050

4.00

17.46

current is shifting

lab probe up &

down a few feet

5-18-00

+.06

0 +.1

852 855 -3

Y

N

Y

Figure 4. Field inspection/calibration sheet—Continued.
10

checking (fig. 4, item 3). The data that were logged by

the DCP since the last visit were downloaded to the

palmtop computer so they could be available in

the event that any data were not transmitted by the satellite system. The clock in the DCP was checked and

adjusted, if necessary. Antenna alignment and recorded

battery voltages were checked and recorded.

The power and charging systems were checked

using a digital multimeter (fig. 4, item 4). Some of the

sites had 120-volt alternating-current (AC) power service; the voltage of those supplies was checked. With

the battery disconnected, its voltage was measured, and

the circuit that charges the battery (the regulator) was

checked. Finally, the battery was reconnected, and the

voltage output of the solar panel or AC/DC converter

was checked before its input to the voltage regulator.

The field-deployed electronic barometer was

checked and adjusted, if necessary (fig. 4, item 5). The

measurement from the secondary standard aneroid

barometer (“Lab BP” on figure 4) was compared to the

measurement made by the field electronic barometer

and displayed by the DCP (“DCP BP” on fig. 4). If there

was a difference, the back shift was applied to change

the offset value in the DCP program. After this step, the

DCP would display the same barometric pressure (to

the nearest millimeter of mercury) as the secondary

standard, the aneroid barometer. The results of the field

calibrations of the electronic barometers at the fixed stations are shown in figure 5. Most of the time, the field

barometer was within 1 mm Hg of the secondary standard. At The Dalles forebay site, the spread of data was

widest—between plus and minus 2 mm Hg. This probably was the result of a variable signal from the electronic barometer, which resulted in the offset being

adjusted one way on one calibration visit and the other

way on the next calibration visit.

The performance of the field temperature sensor

was documented (fig. 4, item 6). The water temperature

measurement made by the secondary standard TDG

probe (“Corrected Lab WT”) was compared to the measurement made by the nearby field-deployed TDG

probe (“Old Field Hyd WT”). The differences were usually less than 0.1oC (degrees Celsius), indicating the

accuracy when compared to the secondary standard (fig.

6).

Performance of the fixed-station TDG sensor was

documented (fig. 4, item 7). Values of TDG obtained by

the secondary standard TDG sensor (“Lab Hyd PT”)

were compared to the values obtained by the fixedstation TDG sensor (“Old Field Hyd PT”). For this

comparison, it was necessary to wait until the seco

standard reached equilibrium in the river. Usually 

equilibration process took about 30 minutes and 

considered to be complete when the reading for e

probe did not change even 1 mm Hg for a period 

minutes. At most sites, there was usually less tha

percent TDG difference between the secondary s

dard and the fixed-station monitor (fig. 7.) At Th

Dalles site once, and at the Camas site three time

TDG measurement from the fixed-station monito

more than 10 percent larger than the measuremen

the secondary standard (fig. 7). These were times 

DIFFERENCE BETWEEN SECONDARY STANDARD AND FIELD BAROMETER, IN MILLIMETERS OF MERCURY

EXPLANATION

10th percentile

25th percentile

Median

75th percentile

90th percentile

10th and 90th percentiles

Data values outside the

JOHN DAY FOREBAY

N=13

-4

4

-2

0

2

BONNEVILLE FOREB

N=23

SKAMANIA

N=14

JOHN DAY TAILWATER

PRIMARY PROBE; N=14

-4

4

-2

0

2

THE DALLES FOREBAY

N=14

WARRENDALE

N=23

-4

4

-2

0

2

CAMAS

N=15

THE DALLES TAILWATER

N=13

-4

4

-2

0

2

5

-6

Figure 5. Difference between the secondary standar

and the field barometers.
11

the TDG membrane had been broken, resulting in incorrect TDG measurements.

The minimum compensation depth was calculated and recorded (fig. 4, item 8). This depth, calculated according to a formula derived from Colt (1984,

page 104), is the depth above which degassing will

occur, due to the decreased hydrostatic pressure. In

order to measure TDG accurately, the probe must be

deeper than the calculated compensation depth. If the

probe was not below minimum compensation depth and

it was physically possible to have it that deep, the TDG

was measured at the larger depth (fig. 4, item 9).

The probe from the fixed station was remo

from the river and the depth parameter was check

when it was above the water surface (fig. 4, items 

11). The depth reading usually differed from zer

about 0.1 or 0.2 feet. These differences were due 

fact that the depth sensor on the TDG probe was 

vented to the outside atmosphere, so that change

barometric pressure affected the measured depth 

TDG probe.

The newly calibrated TDG probe was conn

to the fixed-station equipment, the functions of d

and TDG measurement were checked, and the ze

DIFFERENCE BETWEEN SECONDARY STANDARD AND FIELD THERMOMETER, IN DEGREES CELSIUS

0.2

0.1

0

-0.1

-0.2

0.2

0.1

0

-0.1

-0.2

0.2

0.1

0

-0.1

-0.2

0.2

0.1

0

-0.1

-0.2

0.5

2.1

JOHN DAY FOREBAY

N=13

BONNEVILLE FOREBAY

N=23

SKAMANIA

N=14

JOHN DAY TAILWATER

PRIMARY PROBE; N=14

THE DALLES FOREBAY

N=14

WARRENDALE

N=23

CAMAS

N=15

THE DALLES TAILWATER

N=13

EXPLANATION

10th percentile

25th percentile

Median

75th percentile

90th percentile

10th and 90th percentiles

Data values outside the

Figure 6. Difference between the secondary standard and

the field thermometers.

-6

6

-4

-2

0

2

4

-6

6

-4

-2

0

2

4

-6

6

-4

-2

0

2

4

TOTAL DISSOLVED GAS, IN PERCENT SATURATION

-6

6

-4

-2

0

2

4

JOHN DAY FOREBAY

N=13

BONNEVILLE FOREBAY

N=23

SKAMANIA

N=14

JOHN DAY TAILWATER

THE DALLES FOREBAY

N=14

WARRENDALE

N=23

CAMAS

N=15

THE DALLES TAILWATER

N=13

EXPLANATION

10th percentile

25th percentile

Median

75th percentile

90th percentile

10th and 90th percentiles

Data values outside the

-39.7

-14.5 -16.0 -17.5

Figure 7. Total dissolved gas difference between the

field probe and lab probe initially.
12

point for depth measurement was calibrated (fig. 4, item

12).

The TDG probe was allowed 5 to 10 minutes to

equilibrate in the river then the temperature measurement function was checked and calibrated (fig. 4, item

14). Using the electronic offsets in the DCP, the measurement made by the newly calibrated TDG probe was

made to read the same temperature as measured by the

secondary standard for temperature (the laboratorycalibrated TDG probe).

The final field calibration step (fig. 4, item 15)

was to check the TDG measurement in the river made

by the newly calibrated fixed-station probe against

that made by the secondary standard (the laboratorycalibrated TDG probe). These two values usually were

within 2 percent TDG of each other (fig. 8).

Daily Quality-Assurance Checks

Each morning, the performance of the TDG fixed

stations was evaluated and e-mail concerning the status

of the network was sent to involved parties, including

USACE. Figures 9–11 are examples of the materials

used for the daily quality-assurance checks. Figure 9

shows a checklist summarizing intersite comparisons.

Figure 10 is an example of 1 of 33 pairwise graphs of

TDG, barometric pressure, and temperature data from

adjacent sites made during the spring and summer spill

season; 1 additional graph showed the 2 TDG measurements made at the John Day tailwater site. Data for

graphs of intersite comparisons were from the USGS

ADAPS database, current to approximately 0600 hours

on the day of the check. Also included were data from

the USACE Web site showing spill and total flow below

the dams at John Day, The Dalles, and Bonneville.

These data were included to help explain variations of

TDG that could be related to the changing operations of

the dams above the fixed-station TDG monitors. For

example, figure 11 illustrates the effects of changes in

spill over the John Day Dam on TDG measured at the

John Day tailwater site.

These quality-assurance materials were valuable

for evaluating the status of the monitoring network. If

data were completely missing from one site, the satellite

downlink data were checked to see if signal strength,

transmission time, or battery voltage data were anomalous for previous transmissions.

On occasion during these daily checks, the TDG

values were observed to suddenly increase and stay constant at a larger value, without a corresponding increase

in spill at the dam above the site. In these cases, 

problems were caused by a tear or hole in the TD

membrane, which allowed water pressure to influ

the TDG sensor, which should have been expose

to the air inside the tubular TDG membrane.

When this happened, an “emergency” field 

was made to resolve the problem. In the case that 

were data from a site that were known to be incorr

a result of a damaged membrane or for any other r

this was noted in the daily e-mail to the intereste

ties mentioned previously.

-6

6

-4

-2

0

2

4

-6

6

-4

-2

0

2

4

-6

6

-4

-2

0

2

4

TDG, % SATURATION DIFFERENCE BETWEEN FIELD PROBE AND LAB PROBE AFTER SWITCH

-6

6

-4

-2

0

2

4

JOHN DAY FOREBAY

N=13

BONNEVILLE FOREBAY

N=23

SKAMANIA

N=14

JOHN DAY TAILWATER

PRIMARY PROBE; N=14

THE DALLES FOREBAY

N=14

WARRENDALE

N=23

CAMAS

N=15

THE DALLES TAILWATER

N=13

EXPLANATION

10th percentile

25th percentile

Median

75th percentile

90th percentile

10th and 90th percentiles

Data values outside the

Figure 8. Total dissolved gas difference between the

field probe and lab probe at the end of field calibratio
13

 CHECKLIST FOR TDG DAILY CHECKS - attach to daily graphs

Date____________Checked by_____________

Check the 33 intersite comparison graphs back to the last day checked.

(For example, check back to Friday on Monday).

___ Pt - No more than 25% of the hourly values are missing or anomalous

 (Intersite comparisons differ < 20 mm Hg unless spill explains difference

___ B.P. - No more than 25% of the hourly values are missing or anomalous

 (Intersite comparisons differ < 14 mm Hg)

If these conditions are not met, an emergency trip needs to be taken within

the next 48 hours.

___ Temp. - Check for intersite variations > 2.0 deg C, note to COE, but

 no emergency trip is needed.

Y or N Is replot needed to clearly see data variations on any plot?

If yes - replot data and put the new plot with the daily check.

Y or N Are any data missing from ADAPS but present at COE website?

If yes - put COE data with site file.

 - immediately contact our computer section to restore data

 to ADAPS if possible.

Y or N Were any graphs marked to explain or note any potential anomalies?

If yes - make a copy and put copy in site file.

___ Send email to COE describing site status, including planned emergency trips

If any site is other than satisfactory, include the hour of missing 

questionable data, and put a copy of the email in site file.

ü

ü

ü

6/23/00 Tanner

X

Figure 9. Checklist for total dissolved gas daily quality-assurance checks.

Data Workup and Archive

Periodically, and at the end of the fiscal year, data

for each TDG fixed-station were reviewed in-house and

documented on paper files and in the USGS database.

Tables and graphs of hourly value data were prepared

for TDG, barometric pressure, and water temperature

for each month for which data were collected. These

tables and figures were screened using intersite comparisons between adjacent sites and monthly graphs of spill

from appropriate dams. Any incorrect data were deleted

from the database. Common causes of incorrect data

included elevated TDG measurements due to torn TDG

membranes (mentioned above) and missing value codes

from the satellite transmissions that were interpre

the USGS database as large measured values. An 

tronic file of data to be deleted was prepared for

USACE.

In one case, at the Skamania site from Aug

to September 15, 2000, a linear shift was applied 

TDG data due to the gradual failure of the TDG s

The shifted data were incorporated into the USGS 

base and the same shifted data were supplied to

USACE.

Ancillary data and information were also d

mented in paper files. Data for battery voltage afte

satellite transmission were graphed on a monthly 

in order to track any problems with data transmis
14

950

900

850

800

750

12 13 14 15 16 17 18 19 20 21 22 23

JUNE 2000

TOTAL DISSOLVED GAS PRESSURE, IN MILLIMETERS OF

MERCURY

454257120413000 COLUMBIA RIVER AT JOHN DAY DAM FOREBAY

454249120423500 COLUMBIA RIVER AT JOHN DAY TAILWATER

Figure 10. Total dissolved gas pressure above and below John Day Dam.

Figure 11. Example data table from U.S. Army Corps of Engineers Total Dissolved Gas Reports Web page

(http://www.nwd-wc.usace.army.mil/report/tdg.htm).

 TOTAL DISSOLVED GAS REPORT FOR JOHN DAY TAILWATER 

 starting at 0405 22 jun 2000 

 WA TM BARO TD1 GAS TD2 GAS GAS(1) SPILL TOT

DATE TIME DEG F PRES PRES PRES % S R

0622 0500 62.7 760.0 897.0 890.0 118.03 090.4 153.5

0622 0600 62.7 759.0 897.0 888.0 118.18 083.4 147.6

0622 0700 62.7 760.0 880.0 879.0 115.79 054.3 160.6

0622 0800 62.7 760,0 879.0 875.0 115.66 054.2 176.7

0622 0900 62.8 761.0 879.0 874.0 115.5l 054.2 181.7

0622 1000 62.8 761.0 878.0 873.0 115.37 054.3 185.8

0622 1100 62.8 759.0 879.0 873.0 115.81 058.7 194.9

0622 1200 62.9 760.0 880.0 873.0 115.79 063.9 211.7

0622 1300 62.9 759.0 898.0 887.0 118.31 070.3 230.4

0622 1400 63.0 759.0 898.0 892.0 118.31 070.3 264.1

0622 1500 63.1 760.0 898.0 891.0 118.16 070.5 236.0

0622 1600 63.1 760.0 897:0 891.0 118.03 073.4 235.0

0622 1700 63.1 759.0 904.0 896.0 119.10 081.4 275.8

0622 1800 63.1 760.0 904.0 896.0 118.95 083.0 274.7

0622 1900 63.1 759.0 904.0 895.0 119.10 084.0 264.4

0622 2000 63.1 760.0 898.0 891.0 118.16 136.8 233.5

0622 2100 63.2 761.0 891.0 882.0 117.08 122.2 209.8

0622 2200 63.2 761.0 888.0 880.0 116.69 122.2 207.2

0622 2300 63.1 759.0 887.0 878.0 116.86 124.5 206.8

0623 000 63.1 761.0 886.0 880.0 116.43 122.1 203.0

0623 0100 63.1 760.0 887.0 880.0 116.71 122.1 200.4

0623 0200 M M M M U 118.3 190.7

0623 0300 M M M M U 118.3 200.2

0623 0400 M M M M U 116.4 200.4

STATUS=M, data missing due to lag time between data collection and transmission

STATUS=U, data unavailable (not calculable)
15

due to low battery voltage. The recorded probe depth

was also graphed. E-mail correspondence referring to

each site was also archived in the corresponding site

folder.

SUMMARY OF DATA COMPLETENESS

AND QUALITY

Year-end summaries of water year 2000 TDG

data completeness and quality are shown in table 2.

Data in this table were based on the amount of hourly

TDG data and barometric pressure data that could have

been collected during the scheduled monitoring season.

At all stations, more data were collected than was

scheduled because the monitors were set up early to

ensure correct operation. Because TDG in percent saturation is calculated as total dissolved gas pressure, in

millimeters of mercury, divided by the barometric pressure, in millimeters of mercury, multiplied by 100 percent, any hour with missing TDG pressure data or

missing barometric pressure data was counted as an

hour of missing data for TDG in percent saturation.

The percentage of real-time data received shown in

table 2 represents the data that were received via satellite telemetry at the USGS downlink. The USACE

downlink operated independently, but the amount and

quality of the data were very similar. At each station, 98

percent or more of the data were received real-time by

the USGS downlink, with an overall average of 99.6

percent. Problems with the amount of real-time data

received were usually due to malfunction or misp

gramming of the data-collection platform.

The collection of water temperature data ha

fewer complications than did the collection of TDG 

barometric pressure data. There were only a few h

of missing or incorrect temperature data, except f

instances where all data parameters were missing d

problems with the DCP.

TDG data were considered to meet quality-

ance standards if they were within 1 percent TDG 

expected value, based on calibration data and amb

river conditions at adjacent sites. The percentage 

real-time TDG data passing quality assurance is s

in table 2. The lowest percentage for a station was 

percent at Skamania, but all of the missing data w

eventually restored to the database. The overall av

of real-time data passing quality-assurance standa

was 98.5 percent. Most problems with meeting qu

assurance standards were due to membrane failure—leaking or tearing of the TDG membrane.

QUALITY-ASSURANCE DATA

Duplicate data for John Day tailwater were

collected for TDG only. Data between the two ins

ments compared well, as depicted on figure 12, w

shows how the two probes responded to daily cha

in spill at the John Day Dam. The greatest differe

occurred at times when gas levels changed rapidly

Table 2. Total dissolved gas data completeness and quality, water year 2000

[TDG, total dissolved gas]

Abbreviated station name

Planned

monitoring,

in hours

Percentage of real-time

TDG data received

Percentage of real-time

TDG data passing

quality assurance

John Day forebay 4,032 99.4 99.4

John Day tailwater

 Main probe

 Duplicate probe

4,032

4,032

99.9

99.9

99.9

98.7

The Dalles forebay 4,032 99.5 97.7

The Dalles tailwater 4,032 100.0 100.0

Bonneville forebay 8,784 98.3 98.2

Skamania 4,560 100.0 95.3

Warrendale 8,784 99.9 99.3

Camas 4,560 99.8 98.0

Average 99.6 98.5
16

100.0

105.0

110.0

115.0

120.0

125.0

TOTAL DISSOLVED GAS, IN PERCENT SATURATION

Main probe

Duplicate probe

25 30 5 10

APRIL 2000 MAY 2000

Figure 12. Selected total dissolved gas data at the main and duplicate probes at John Day tailwater.

result of each probe responding at a different rate.

Future deployment of redundant probes should have

paired membranes with the same age and use, to reduce

differences in response time.

A slight bias existed between the two probes as

depicted by figure 13, which represents 4,317 hourly

values from March 23 to September 18, 2000. The

duplicate probe was 1 foot higher in the water column

and tended to read lower than the main probe. A likely

cause of this bias may be a reduced flow over the membrane on the duplicate probe. Perforations in the housing were originally intended for one probe located at the

end of the housing. This concern will be eliminated by

installing two adjacent TDG sensors on the same

Hydrolab.

Duplicate TDG and water temperature data 

collected at the John Day forebay from 4/5/2000 a

hours to 4/12/2000 at 1400 hours. The duplicate 

was mounted approximately 6 feet horizontally f

the main probe at the same depth. The duplicate 

were collected to confirm the rapid changes in tem

ture and TDG above the John Day Dam that did 

occur below the dam, as depicted in figures 14 an

TDG and water temperature measured by the ma

probe compared well with the duplicate probe. Ba

the strong correlation between the two units, the 

changes in water temperature and TDG appear to b

and not a problem with instrumentation. The cau

these rapid changes is not known at this time; how

it is suspected that water near the probes is not w

mixed and occasionally water in the vertical sect

transported across the face of the dam by certain 

patterns that cause poorly mixed water to flow ov

probes.

SITE-SPECIFIC CONSIDERATIONS

Even though the same type of electronic eq

ment and instruments were used at each site, there 

differences among the sites in the physical setup 

environment of equipment. Some sites were at a 

location with limited depth, some had greater cir

tion of water past the probe, and some were pron

damage by insects. These site-specific considera

are summarized below for each of the eight sites

N = 4,317

-8.0

10.0

-6.0

-4.0

-2.0

0

2.0

4.0

6.0

8.0

TOTAL DISSOLVED GAS, IN PERCENT SATURATION

EXPLANATION

10th percentile

25th percentile

Median

75th percentile

90th percentile

10th and 90th percentiles Data values outside the

Figure 13. All of the total dissolved gas data at the main

and duplicate probes at John Day tailwater.
17

8.0

8.5

9.0

9.5

10.0

10.5

11.0

11.5

5 6 7 8 9 10 11 12

APRIL 2000

WATER TEMPERATURE, IN DEGREES CELSIUS

John Day forebay

John Day tailwater

John Day forebay duplicate

Figure 14. Duplicate water temperature data at John Day forebay and water temperature data at John Day tailwater.

760

770

780

790

800

810

820

5 6 7 8 9 10 11 12

APRIL 2000

TOTAL DISSOLVED

G

AS, IN MILLIMETERS OF MERCURY

Main probe

Duplicate probe

Figure 15. Duplicate total dissolved gas data at John Day forebay.

Camas

At the Camas site, there were three separate occasions (June 29, July 23, and July 31, 2000) when the

TDG membrane was pierced by aquatic insects, which

were observed inside the probe housing. When this happened, the hole in the membrane allowed water pressure

instead of dissolved gas pressure to act on the TDG

pressure sensor. As a result, the measured values for

TDG rose suddenly to about 1,000 mm Hg, even t

there was not an unusual amount of spill from Bo

ille Dam, which is upstream of the Camas site. T

condition was diagnostic of a broken membrane, 

accordingly, an emergency field trip was made to

replace the probe with a newly calibrated probe. D

the third trip due to a damaged membrane, screen

was added to the probe to exclude insects, and the 

lem did not reoccur. TDG data that were lost due 
18

type of damage were not recoverable because there is no

way to know precisely what would have been recorded

at those times.

Also at the Camas site, the barometer was

adjusted incorrectly, resulting in a bias of -5 mm Hg for

21 hours beginning on June 5, 2000, at 1200 hours. The

barometer was readjusted, and the 21 hours of data were

corrected in the database.

Skamania

At Skamania, a newly calibrated probe was

placed in the river on August 30, 2000, at 1036 hours.

The following day, scheduled spill ended for the season

at Bonneville Dam, just upstream. As a result, the TDG

was expected to decrease at the Skamania site, and a

decrease was observed. However, the TDG eventually

decreased to levels lower than would be expected.

When the probe was inspected, it was found to have a

faulty sensor, which accounted for the TDG readings

being too low. Subsequently, a linear shift was applied

to the data, with no shift for August 30 at 1100 hours,

and shifts increasing until a final shift of +56 mm Hg on

September 18 at 1100 hours. This was an example of

data being transmitted in a real-time manner, but not

being correct. Further, in this case, the data were correctable because the gradual decline in TDG readings

(with no change in spill) was consistent with a gradually

failing TDG sensor.

Warrendale

At Warrendale, there was a faulty TDG sensor,

which resulted in erratic TDG values from February 29,

2000, at 1300 hours until March 2, 2000, at 0800 hours.

The sensor was replaced, but there was no way to correct the data in question, so it was deleted from the database.

Compensation depth for TDG measurement is the

depth above which degassing will occur. In order to

measure TDG accurately, the probe must be deeper than

the compensation depth, which is calculated as [TDG

pressure, in millimeters of mercury, minus barometric

pressure, in millimeters of mercury] divided by 23 (a

constant). This equation was based on a formula derived

from Colt (1984, page 104). If the probe is above the

minimum compensation depth, the measured TDG may

be less than it would be if measured at a greater depth.

The compensation depth can be calculated for

any given percent saturation of TDG if an assumption is

made for the barometric pressure. For example, i

barometric pressure is assumed to be 760 mm Hg

the TDG level is 120%, the TDG pressure would b

mm Hg (120% of 760 mm Hg), and the compens

depth would be [912 - 760]/23 = 6.6 feet. Using 

same assumption for barometric pressure, at a TD

level of 145%, the compensation depth would be 

feet. Where possible, the TDG probes were kept 

depth of 15 feet or greater.

Warrendale was the only site where the TD

probe was above the compensation depth at any t

water year 2000. After the end of the spill on Augu

2000, the river stage had dropped, but supersatur

water remained in the river from upstream dams, 

ing in the probe depth being above the compensa

depth for several days (fig. 16). This was becau

the physical characteristics of the site. The instru

were housed on a floating wooden dock, and the 

probe was suspended from the dock. When the riv

shallow at the Warrendale site, as it was in early 

tember, the probe depth was about 4 feet because 

was the total depth of the river below the dock at 

time. In order to measure TDG at a greater depth

probe would need to be moved to a deeper part o

river, but that was not possible because of the fixe

tion of the site.

Bonneville

At the Bonneville site, there were data tran

sion problems from January 1 to January 5, 2000, 

ing in 46 hours of missing real-time TDG data. T

cause of this missing data is unknown, but it may 

been due to large cranes that work in the dam are

which have been known to sometimes be placed

between the DCP antenna and the orbiting satellit

occluding the satellite. These 46 hours of TDG d

were restored to the permanent database using th

logged onsite by the DCP.

From July 21 to July 25, 2000, 91 hours of 

were missing from the Bonneville site due to fail

the DCP. In this case, the data were not logged o

so it was not possible to restore the data to the dat

The Dalles Tailwater

Only 2 hours of TDG data were missing fr

The Dalles tailwater site. One datum was missing 

calibration activities on July 20, 2000, and the ca

loss of the other datum is not known.
19

-2

0

2

4

6

8

10

12

14

10/1 11/20 1/9 2/28 4/18 6/7 7/27 9/15

WATER YEAR 2000

Actual probe depth

Compensation depth

DEPTH BELOW ATER SURFACE, IN FEET

Figure 16. Compensation depth and actual probe depth at Warrendale.

The probe housing at The Dalles tailwater site is

strapped to anchors along a slope of rock rip-rap. On

several occasions during the monitoring season, the probe

housing was raised or lowered according to the river stage.

In this manner, it was possible to maintain the probe depth

below the minimum compensation depth.

The Dalles Forebay

TDG data were missing from The Dalles forebay site

for a 72-hour period from April 15 to April 18, 2000, due

to a ruptured TDG membrane. It was not possible to

restore these data to the database.

DCP problems from August 29 to September 5,

2000, were the cause of 19 hours of data that were missing

in real-time. These data were later restored to the database

from the data logged onsite by the DCP.

John Day Tailwater

For the duplicate unit at the John Day tailwater site,

45 hours of TDG data were missing from September 4 to

September 6, 2000, due to a rupture or tear in the TDG

membrane. These data could not be restored. There were

only 3 hours of missing TDG data for the main unit at John

Day tailwater.

John Day Forebay

Beginning on August 3, 2000, 23 hours of TDG data

were missing from the John Day forebay site due to an

error in reconnecting the electronic barometer during a

routine calibration. These data could not be re

database.

On several occasions at the John Day fo

TDG value was observed to suddenly rise 10 o

for several hours for no apparent reason. It wa

the water temperature also rose during these ti

excursions of TDG and water temperature we

on hot, sunny days, and it is believed that a par

water was drawn past the submerged TDG pro

spill, causing the increase in water temperatur

measured at the probe would be expected to a

because when a gas is heated and the volume i

is inside the TDG membrane), the pressure of 

increase.

REFERENCES CITED

 Colt, J. 1984. Computation of dissolved gas conce

water as functions of temperature, salinity, an

American Fisheries Society Special Publicati

Jones, J.C., Tracey, D.C., and Sorensen, F.W., eds.

ating manual for the U.S. Geological Survey’

tion system with the Geostationary Operation

Environmental Satellite: U.S. Geological Surv

Report 91–99, 237 p.

Tanner, D.Q., Harrison, H.E., and McKenzie, S.W

dissolved gas, barometric pressure, and water 

data, lower Columbia River, Oregon and Wash

U.S. Geological Survey Open-File Report 96

U.S. Environmental Protection Agency, 1986, Qual

water: Washington, D.C., EPA–440–5–86–00