Total Dissolved Gas and Water Temperature in the Lower Columbia River Oregon and Washington Water Year 2009

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 monitoring stations on the lower Columbia River in Oregon and Washington in 2009. Significant findings from the data include: During the spill season of April through August 2009, hourly values of total dissolved gas (TDG) were occasionally larger than 115-percent saturation for the forebay stations (John Day navigation lock, The Dalles forebay, Bonneville forebay, and Camas). Hourly values of total dissolved gas were occasionally larger than 120-percent saturation for two tailwater stations (John Day Dam tailwater and Cascade Island). From mid- to late July to mid-September 2009, water temperatures were greater than 20 degree(s) C (degrees Celsius) at seven stations on the lower Columbia River. According to the State of Oregon temperature standard, the 7-day average maximum temperature of the lower Columbia River should not exceed 20 degree(s)C; Washington regulations state that the 1-day maximum should not exceed 20 degree(s) C as a re-sult of human activities. All 96 laboratory checks of the TDG sensors with a certified pressure gage were within 0.4 percent saturation after 3 to 4 weeks of deployment in the river. All but 2 of the 73 in situ field checks of TDG sensors with a secondary standard were within + or - (plus or minus) 1.0-percent saturation after 3-4 weeks of deployment in the river. All 74 of the field checks of barometric pressure were within + or - 2.0 millimeters of mercury of a secondary standard, and all 65 water-temperature field checks were within + or - 0.2 degree(s) C. For the eight monitoring stations in water year 2009, a total of 99.2 percent