Total dissolved gas and water temperature in the lower Columbia River, Oregon and Washington, 2005: quality-assurance data and comparison to water-quality standards

Significant Findings

When water is released through the spillways of dams, air is entrained in the water, increasing the downstream concentration of dissolved gases. Excess dissolved-gas concentrations can have adverse effects on freshwater aquatic life. The U.S. Geological Survey (USGS), in cooperation with the U.S. Army Corps of Engineers, collected dissolved-gas and water-temperature data at eight sites on the lower Columbia River in 2005. Significant findings from the data include:

• Variances to the Oregon and Washington water-quality standards for total dissolved gas were exceeded at five of the monitoring sites: Camas (11 days), John Day tailwater (3 days), The Dalles forebay (3 days), Bonneville forebay (3 days), and John Day navigation lock (1 day).
• From mid-July to early September, water temperatures were above 20°C (degrees Celsius) at each of the eight lower Columbia River sites. According to the Oregon temperature standard, the 7-day average maximum temperature of the lower Columbia River should not exceed 20°C; Washington regulations state that the 1-day maximum should not exceed 20°C due to human activities.
• Most field checks of total-dissolved-gas sensors with a secondary standard were within ± (plus or minus) 1% saturation. Most of the field checks of barometric pressure were within ±1 millimeter of mercury of a secondary standard, and water temperature field checks were all within ±0.2°C.
• For the eight monitoring sites in water year 2005, an average of 98.2% of the total-dissolved-gas data were received in real time by the USGS satellite downlink and were within 1% saturation of the expected value, based on calibration data, replicate quality-control measurements in the river, and comparison to ambient river conditions at adjacent sites.