Water consumption from hydropower plants - review of published estimates and an assessment of the concept

Since the report from IPCC on renewable energy (IPCC, 2012) was published; more studies on water consumption from hydropower have become available. The newly published studies do not, however, contribute to a more consistent picture on what the true water consumption from hydropower plants is. The dominant calculation method is the gross evaporation from the reservoirs divided by the annual power production, which appears to be an over-simplistic calculation method that possibly produces a biased picture of the water consumption of hydropower plants. This review paper shows that the water footprint of hydropower is used synonymously with water consumption, based on gross evaporation rates. This paper also documents and discusses several methodological problems when applying this simplified approach (gross evaporation divided by annual power production) for the estimation of water consumption from hydropower projects. A number of short-comings are identified, including the lack of clarity regarding the setting of proper system boundaries in space and time. The methodology of attributing the water losses to the various uses in multi-purpose reservoirs is not developed. Furthermore, a correct and fair methodology for handling water consumption in reservoirs based on natural lakes is needed, as it appears meaningless that all the evaporation losses from a close-to-natural lake should be attributed to the hydropower production. It also appears problematic that the concept is not related to the impact the water consumption will have on the local water resources, as high water consumption values might not be problematic per se. Finally, it appears to be a paradox that a reservoir might be accorded a very high water consumption/footprint and still be the most feasible measure to improve the availability of water in a region. We argue that reservoirs are not always the problem; rather they may contribute to the solution of the problems of water scarcity. The authors consider that an improved conceptual framework is needed in order to calculate the water footprint from hydropower projects in a more reasonable way.