Heather M. Bragg
Matthew W. Johnston
Dwight Q. Tanner
2011
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<p>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 2010. Significant findings from the data include:</p>
<ul>
<li>During the spill season of April through August 2010, 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 four tailwater stations (John Day Dam tailwater, The Dalles tailwater, Cascade Island, and Warrendale).</li>
<li>From late July to late August or early September 2010, hourly water temperatures were greater than 20°C (degrees Celsius) at the eight 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°C Washington regulations state that the 1-day maximum should not exceed 20°C as a result of human activities.</li>
<li>All 105 laboratory checks of the TDG sensors (without the membrane attached) with a certified pressure gage were within ± (plus or minus) 0.5 percent saturation after 3 to 4 weeks of deployment in the river.</li>
<li>All but 1 of the 85 in situ field checks of TDG sensors with a secondary standard were within <span>±</span>2.0-percent saturation after 3-4 weeks of deployment in the river. All 88 of the field checks of barometric pressure were within <span>±</span>1 millimeter of mercury of a primary standard, and all 87 water-temperature field checks were within <span>±</span>0.2<span>°</span>C of a secondary standard.</li>
<li>For the eight monitoring stations in water year 2010, a total of 99.7 percent of the TDG data were received in real time and were within 1-percent 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. Data received from the individual stations ranged from 98.4 to 100.0 percent complete.</li>
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application/pdf
10.3133/ofr20101293
en
U.S. Geological Survey
Total dissolved gas and water temperature in the lower Columbia River, Oregon and Washington, water year 2010: Quality-assurance data and comparison to water-quality standards
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