Selecting a small run-of-river hydropower plant by the analytic hierarchy process (AHP): A case study of Miño-Sil river basin, Spain

•The number of small hydropower plants can increase around the world.•Small run-of-river hydropower plants must be subjected to EIA process.•Multi criteria decision analysis techniques are very suited to this type of problem.•The AHP method is applied to select the best alternative from three viable ones.•Protected fauna, water quality and fish population are the main identified factors. Hydroelectric power is obtained by harnessing the potential energy of a mass of water flowing along a river bed to convert it first into mechanical and then into electrical energy. The system is therefore both clean and autonomous and has a high potential for development. A small hydropower plant has an installed power capacity of below 10MW and is considered run-of-river when it diverts part of a river flow to generate its electricity. The use of multicriteria techniques in environmental decision making, including selecting between various alternatives, is important when it involves complex decisions in a number of disciplinary fields. The most widely used of these techniques is the analytic hierarchy process (AHP). This work proposes an application of the AHP method to select the best alternative for the installation of a small run-of-river hydropower plant. The systemization of the process, together with its mathematical rigor, means the best project will be selected from the available technical, economic and environmental alternatives. The main criteria identified in this study for the selection of RoR plant are: protected fauna, fish population, water quality, landscape quality, flow regime and vegetation. Finally, the best alternative was the project of the company Energia of Galicia.