Opinion ID: 411109
Heading Depth: 3
Heading Rank: 5

Heading: Supersaturation

Text: 15 When water plunges at high velocity from the reservoir into the downstream river, it becomes mixed with air. Depending on the velocity and turbulence of the falling water and the depth of the receiving basin, this can cause downstream water to become supersaturated--aerated in excess of normal concentration. Supersaturated water does not harm people and is suitable for most uses, but can be fatal to fish; documented fish kills have occurred at a number of dams. 17 16 Supersaturation can be prevented or reduced to non-fatal levels by reducing the turbulence of the falling water (water released from a spillway at the top of a dam is more turbulent than water released through a pipe in the dam), increasing reservoir capacity to reduce the need for spillway releases during flood periods, using a shallow receiving basin below the dam, or constructing spillway deflectors. 18 Supersaturation does not appear at present to be a major problem. The most recent fish kills discussed in the record occurred at Truman Dam in Missouri in 1978 and 1979 while the dam was under construction, and subsequent installation of a spillway deflector has reduced supersaturation to non-fatal levels. 19