US Army Corps of Engineers
Northwestern Division

Total dissolved gas
In addition to several fish passage systems in place at the lower Columbia River and lower Snake River dams, spillway deflectors produce a more horizontal spill flow and limit the plunge depth of water over the dam spillway. This reduces the amount of entrained nitrogen that creates total dissolved gas, or TDG.

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Photo by: Army Corps of Engineers |  VIRIN: 190925-A-A1408-001.JPG