Supersaturation in hydropower installations

Abstract

Gas supersaturation occurs when the amount of dissolved gas in water exceeds the solubility for the given local pressure. Such conditions may happen in natural watercourses, but more observations are associated with hydropower installations in rivers. The main anthropogenic sources either originate from water spilled over dams into deep pools or from air entrained through tunnel systems in hydropower plants. Supersaturated water in rivers have significant ecological consequences to aquatic biota. This report provides a literature review of the available reports and publications regarding supersaturation from hydropower installations. The main focus is on high-head HPPs with secondary intakes, which is the most common source of supersaturation in Norway. This report provides an overview of the physical processes, main sources of supersaturation associated with in hydropower installations and mitigation measure.