Total Dissolved Gas and Water Temperature in the Lower Columbia River, Oregon and Washington, Water Year 2013: Quality-assurance data and comparison to water-quality standards

Significant Findings

An analysis of total-dissolved-gas (TDG) and water-temperature data collected at eight fixed monitoring stations on the lower Columbia River in Oregon and Washington in water year 2013 indicated the following:

• During the spill season of April–August 2013, the averages of the 12 highest hourly TDG values in a day were periodically greater than 115-percent saturation for the forebay stations (John Day navigation lock, The Dalles forebay, and Bonneville forebay) and the Camas station. The 12 highest average daily values of TDG were also periodically greater than 120-percent saturation at Cascade Island. TDG values at the other tailwater stations (John Day Dam tailwater, The Dalles tailwater, and Warrendale) did not exceed 120-percent saturation.
• During parts of July, August, and September 2013, hourly water temperatures were greater than 20 degrees Celsius at all eight monitoring stations on the lower Columbia River.
• All of the 98 TDG sensor laboratory checks that were performed after field deployment were within ±0.5-percent saturation of a primary standard.
• After 3–4 weeks of deployment in the river, all but 1 of 85 TDG sensor field checks were within ±1.0-percent saturation of a secondary standard. All but 1 of 87 barometric pressure field checks were within ±1 millimeter of mercury of a primary standard, and all 86 water-temperature field checks were within ±0.2 degrees Celsius of a secondary standard.
• For the eight monitoring stations, a total of 99.2 percent of the TDG data were received in real time and were within 1-percent saturation of the expected value on the basis of calibration data, replicate quality-control measurements, and comparison to river conditions at adjacent sites. Data completeness for the monitoring stations ranged from 97.7 to 100 percent.
• All quality-assurance and data completeness values exceed the criteria established by the U.S. Army Corps of Engineers TDG monitoring plan.

First posted August 19, 2014