When water is released through the spillways of dams, air is entrained in the water, increasing the concentration of total dissolved gas. 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 total- dissolved-gas and water-temperature data at seven sites on the lower Columbia River in 2003. Significant findings from the data include:

• For the seven monitoring sites in water year 2003, an average of 98.9% 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.
• Most field checks of total-dissolved-gas sensors with a secondary standard were within plus or minus 1% saturation. Field checks of barometric pressure and water temperature were usually within plus or minus 1 millimeter of mercury and plus or minus 0.1 degree Celsius, respectively.
• The variances to the States of Oregon and Washington water-quality standards for total dissolved gas were exceeded at six of the seven monitoring sites. The sites at Camas and Bonneville forebay had the most days exceeding the variance of 115% saturation. The forebay exceedances may have been the result of the cumulative effects of supersaturated water moving downstream through the lower Columbia River. Apparently, the levels of total dissolved gas did not decrease rapidly enough downstream from the dams before reaching the next site.
• From mid-July to mid-September, water temperatures were usually above 20 degrees Celsius at each of the seven lower Columbia River sites. According to the Oregon water-quality standard, when the temperature of the lower Columbia River exceeds 20 degrees Celsius, no measurable temperature increase resulting from anthropogenic activities is allowed. Transient increases of about 1 degree Celsius were noted at the John Day forebay site, due to localized solar heating.