Water quality studies for hydro licenses

Three case studies of the impact of hydroelectric power station operation on dissolved oxygen concentration performed for hydro licence applications are discussed. A negative impact results from the fact that discharges previously aerated over a spillway are substituted by turbine discharges from lower reservoir levels, usually having lower dissolved oxygen concentrations. The methodology used, including field measurements, data analysis, and proposed mitigation measures, is outlined. Although the three cases were similar in power output, the impact was found to be quite different in each case, depending on reservoir morphology, productivity and structure type. (A)