A proposal to save fish from a potentially fatal sickness caused by dissolved gases in spill waters has suggested shifting spills from the Grand Coulee dam on the Columbia river to the Chief Joseph dam further downstream.

The state of Washington Department of Ecology and the US Environmental Protection Agency are jointly seeking public comment on the proposed plan to ‘clean up Columbia waters from dissolved gases. The resulting loss of power production at Chief Joseph would be compensated by increased production at Grand Coulee.

The proposal identifies ways to reduce the total dissolved gas (TDG) content in the Mid-Columbia river and Lake Roosevelt. The tolerable amount of TDG in river water is often exceeded at hydro dams during spillage. Hydro dams discharge excess water via spillways during periods of high inflows or when power demand is small. The spilled water mixes into the river water at high pressure causing an increase in TDG content and ‘gas-bubble trauma’ in fish, a condition similar to ‘the bends’ suffered by scuba divers. Seven dams in the Mid-Columbia are potential caused of increased TDG.