Comparing Options for Improving Dissolved Oxygen Below Hydropower Dam

Abstract

Many existing dams will have to address issues of minimum dissolved oxygen concentration and minimum flow before they can be relicensed. All new hydropower applications also must address such issues. Although technology has been developed to reaerate hydropower releases, trade‐offs exist between oxygen levels in the release and the minimum flow provided in relation to downstream assimilative capacity. A case history beginning with the development of the aeration technology followed by the analysis of the impacts of increased dissolved oxygen concentration and river flow on assimilative capacity is presented. Testing of both in‐reservoir oxygen injection systems and turbine aeration systems is described. A modified Streeter‐Phelps model was used to evaluate the effectiveness of aerating the releases and increasing the minimum flows from the dam. The effects of reducing municipal and industrial waste load on dissolved oxygen concentration were also compared to the effects of aerating the releases and changing minimum river flow. For this particular case, increasing minimum flows was found to be one of the most attractive alternatives for increasing the minimum dissolved oxygen concentration predicted in the river.