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Data Collection Methods, Quality Assurance Data, and Site Considerations for Total Dissolved Gas Monitoring, Lower Columbia River, Oregon and Washington, 2000.
Entry ID: WRIR_01_4005

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

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 model for modeling the effect of various management scenarios of
stream flow and spill on TDG levels.

Instrumentation at each fixed station consisted of a TDG probe, an electronic
barometer, a data-collection platform (DCP), and a power supply. The TDG probe
was manufactured by Hydrolab Corporation. The probe had individual sensors for
TDG, temperature, and probe depth (unvented sensor). The TDG sensor consisted
of a cylindrical framework wound with a length of Silastic (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 presure 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. More information abou the TDG probe is provided by
Tanner, D. Q. And Johnston and M.W. 2001.

The fixed station monitors were calibrated every 2 weeks from March 10 to
September 15, 2000, and every three weeks for the remainder of the year, at
which time Warrendale and Bonneville forebay were the only sites in operation.
The general procedure was to check the operation of the TDG probe in the field
without disturbing it, replace the field probe with one that had just been
calibrated in the laboratory, and then check the operation of the newly
deployed field probe. The details of the laboratory calibration procedure are
outlined in Tanner and Johnston, 2001.

Information for this metadata was obtained from the Technical Reports of the
Oregon District available at .

Geographic Coverage
 N: 46.5 S: 44.75  E: -120.0  W: -124.0

Data Set Citation
Dataset Originator/Creator: Dwight Q. Tanner and Matthew W. Johnson
Dataset Title: Data Collection Methods, Quality Assurance Data, and Site Considerationsfor Total Dissolved Gas Monitoring, Lower Columbia River, Oregon and Washington, 2000.
Dataset Release Date: 2001
Dataset Release Place: Portland, Oregon
Dataset Publisher: U.S. Geological Survey
Data Presentation Form: database

Temporal Coverage
Start Date: 2000-03-01
Stop Date: 2000-09-15

Location Keywords

Science Keywords

ISO Topic Category

Duplicate data for John Day tailwater were collected for TDG only. Data
between the two instruments compared well, as depicted on figure 12 in Tanner
and Johnston, 2001, which shows how the two probes responded to daily changes
in spill at the John Day Dam. The greatest differences occurred at times when
gas levels changed rapidly, as a 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 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 were collected at the John Day forebay from 4/5/2000 at 1600
hours to 4/12/2000 at 1400 hours. The duplicate probe was mounted
approximately 6 feet horizontally form the main probe at the same depth. The
duplicate data were collected to confirm the rapid changes in temperature and
TDG above the John Day Dam that did not occur below the dam. TDG and water
temperature measured by the main probe compared well with the duplicate probe.
Based on the strong correlation between the two units, the rapid changes in
water temperature and TDG appear to be real and not a problem with
instrumentation. The cause of these rapid changes is not known at this time;
however, it is suspected that water near the probes is not well mixed and
occasionally water in the vertical section is transported across the face fo
the dam by certain spill patterns that cause poorly mixed water to flow over
the probes.

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 was 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 millimters 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 hour of
missing data for TDG in percent saturation. The percentage of real-time data
received 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 misprogramming of the data-collection platform.
The collection of water temperature data had fewer complications than did the
collection of TDG and barometric pressure data. There were only a few hours of
missing or incorrect temperature data, except for instances where all data
parameters were missing due to problems with the DCP. TDG data were considered
to meet quality-assurance standars if they were within 1 percent TDG of the
expected value, based on calibration data and ambient river conditions at
adjacent sites. The percentage of real-timeTDG data passing quality assurance
is shown in Table 2 (Tanner and Johnson, 2001) The lowest percentage for a
station was 95.3 percent at Skamania, but all of the missing data was
eventually restored to the database. The overall average of real-time data
passing quality-assurance standards was 98.5 percent. Most problems with
meeting quality-assurance standards were due to membrane failure-leaking or
tearing of the TDG membrane.

Access Constraints

Use Constraints

data collection methods
quality assurance data
site considerations
total dissolved gas monitoring
Lower Columbia River
Dalles Tailwater
Dalles Forebay
John Day Tailwater
John Day Forebay
Biological Data Profile

Data Set Progress

Data Center
Water Resource Division, Oregon, U.S. Geological Survey, U.S. Department of the Interior    [Information]
Data Center URL:

Data Center Personnel
Phone: (503) 251-3200
Fax: (503) 251-3470
Email: ddlynch at
Contact Address:
U.S. Geological Survey
10615 S.E. Cherry Blossom Drive
City: Portland
Province or State: Oregon
Postal Code: 97216-3159
Country: USA

Phone: (503) 251-3289
Email: dqtanner at
Contact Address:
10615 SE Cherry Blossom Drive
City: Portland
Province or State: Oregon
Postal Code: 97216
Country: USA

Phone: (301) 614-6898
Fax: 301-614-5268
Email: Tyler.B.Stevens at
Contact Address:
NASA Goddard Space Flight Center
Global Change Master Directory
City: Greenbelt
Province or State: MD
Postal Code: 20771
Country: USA

Tanner, D.Q., and Johnson, M.W., 2001, Data-collection methods, quality
assurance data and site considerations for total dissolved gas monitoring,
Lower Columbia River, Oregon and Washington, 2000 U.S. Geological Survey,
Water-Resources Investigations Report 01-4005 Portland, Oregon, U.S. Geological

Creation and Review Dates
DIF Creation Date: 2001-06-27
Last DIF Revision Date: 2016-01-27
Future DIF Review Date: 2002-06-27

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