Field Study On The Dissipation Of Supersaturated Total Dissolved Gases In A Cascade Reservoir System

Assessment of the dissipation of total dissolved gases (TDGs) is important in the downstream of hydropower facilities which often encounter TDG supersaturation. An analysis of the two consecutive spill events at the Peace River hydropower system, which includes the Bennett Dam and the Peace Canyon Dam, showed that the percent saturation of TDG and dissolved oxygen (DO) varied with spill rates, pre and post-spill conditions. The decay of TDG was comparatively slower than DO and the rates decreased with the drop of spill flows. For spill of 1,160 m(3)/s at the Peace Canyon Dam, the decay rate for TDG at the dam tailrace and at a distance 7 km downstream was found to be 0.005 and 0.0014 hr(-1), respectively. A conceptual computational fluid dynamics model of the reservoir indicated that density driven currents could affect the TDG dissipation.