Publication Summary

Total dissolved gas (TDG) was monitored in the Columbia River at Wells Dam and in the Snake River at Lower Granite Dam, May through July 2002. Data will support the development of a total maximum daily load for TDG. One meter was deployed at a tailwater mooring, while readings were collected with a second meter from a boat. Data showed TDG changes over time and laterally across the channel, but did not show conditions close to the spillways of the dams or longitudinally downstream. Recommendations are provided on improvements to future field TDG measurements.

Total dissolved gas (TDG) was monitored in the Columbia River at Wells Dam and in the Snake River at Lower Granite Dam during four surveys (two at each site) in May through July 2002. Data will support the development of a total maximum daily load for TDG in the Mid Columbia and Lower Snake rivers. A data logging meter was deployed at a tailwater mooring, while readings were collected with a second meter from a boat while motoring or drifting. Data showed TDG changes over time and laterally across the channel. However, the method did not allow for accurate measurements close to the spillways of the dams, which limited its ability to show longitudinal variation. Field data did not correlate well with fixed monitoring station data. Recommendations are provided on improvements to field TDG measurements for future work.