Quality-assurance data, comparison to water-quality standards, and site considerations for total dissolved gas and water temperature, lower Columbia River, Oregon and Washington, 2001

Significant Findings

• For eight monitoring sites, in water year 2001, an average of 99.3% of the total-dissolved-gas data were received in real time and passed quality-assurance checks.
• After 2 to 3 weeks of deployment in the river, most comparisons of field total-dissolved-gas sensors with a secondary standard (another calibrated total-dissolved-gas sensor) were within 1%.
• The only exceedances of Oregon water-quality standards for total dissolved gas occurred on May 23 and 24, 2001, at the Camas, Washington, station.
• At the forebay of the John Day Dam, temporary increases in water temperature and total dissolved gas occurred on hot afternoons during periods of low wind. These increases were not observed at the John Day tailwater station.
• At Camas, Washington, daily variations of total dissolved gas were probably due to the production of oxygen by aquatic plants and to water-temperature variations on warm, sunny days.
• During spill over Bonneville Dam in water year 2001, the site on the Oregon side of the Columbia River, Warrendale, measured larger total-dissolved-gas levels than the site directly across on the Washington side at Skamania.
• Apparently, streamflow through generating facilities on the north side of the dam forced supersaturated water from the spill bays over to the Oregon side of the river.
• At times in July and August 2001, the total-dissolved-gas probe at Warrendale could not be positioned below the minimum compensation depth because the river was too shallow at that location. Consequently, degassing at probe depth may have occurred, and total dissolved gas may have been larger in locations with greater depths.