Total dissolved gas and water temperature in the lower Columbia River, Oregon and Washington, 2007: 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 2007. Significant findings from the data include:

• From early July to mid-September 2007, 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 in-situ field checks of total-dissolved-gas sensors with a secondary standard were within ± (plus or minus) 1% saturation after 3 to 4 weeks of deployment in the river. All of the field checks of barometric pressure were within ±2.5 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 2007, an average of 99.5% 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 on the basis of calibration data, replicate quality-control measurements in the river, and comparison to ambient river conditions at adjacent sites. Data received from the sites ranged from 97.9% to 100.0% complete.