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 ad-verse effects on freshwater aquatic life. The U.S. Geological Survey (USGS), in cooperation with the U.S. Army Corps of Engineers, collected dissolved-gas concentration and water-temperature data at eight stations on the lower Columbia River in 2006. Significant findings from the data include:
- Variances to the Oregon and Washington water-quality standards for total dissolved gas were exceeded at all of the monitoring stations: Cascade Island (67 days), Camas (60 days), Bonneville forebay (51 days), The Dalles forebay (36 days), John Day tailwater (35 days), John Day navigation lock (20 days), The Dalles tailwater (8 days), and Warrendale (4 days).
- From early July to the end of August 2006, water temperatures were above 20°C (degrees Celsius) at each of the eight lower Columbia River stations. 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. All 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 stations in water year 2006, an average of 99.1% 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 stations.
