Aerating weirs for environmental enhancement of hydropower tailwaters

Abstract

Aerating weirs were used to enhance dissolved oxygen during hydropower generation and to enhance minimum flow between periods of generation. Two different types of weirs (labyrinth and infuser) were designed, constructed, and field tested for performance. The labyrinth is characterized by an extended crest length with a “W” shape in plan view, while the infuser is acting as a broadcrest weir with flow through it. In plan view, the infuser is more compact in the channel, with the appearance of a broadcrest weir. Both exhibited excellent aeration characteristics in performance testing, achieving 55 percent to 70 percent aeration efficiency, where aeration efficiency is defined as a fraction of the oxygen deficit removed by weir aeration. The labyrinth exhibited somewhat more aeration per unit drop height than the infuser. In terms of economy of construction, the infuser appears more favorable in situations of high river specific discharge (>1.9 m2 s−1), while the labyrinth is more favorable in low river flow situations (<0.9 m2 s−1). In the intermediate range, economics of both are comparable, and other site-specific factors are required to assess the best choice. © 1995 Taylor & Francis Group, LLC.