Infodoc : Sciences, Techniques et Culture

The determination of minimum instream flow downstream from hydroelectric impoundments is composed of different aspects including social choices and technical evaluations. The available techniques, from purely hydrological methods to more complex biological models, are rapidly displayed to show that many helps in decision already exist. Besides, the relationships between hydrology and hydroecology are quite important now. The recurrent difficulty to obtain a consensus in the final decision lies more in the fact that the objectives are often not clear, and that the social evolutions towards ecological concerns are not well accepted. The result is that scientists are usually asked to improve again the methods instead of having the right debate. Among different solutions, the most importa[...]

The determination of minimum instream flow downstream from hydroelectric impoundments is composed of different aspects including social choices and technical evaluations. The available techniques, from purely hydrological methods to more complex biological models, are rapidly displayed to show that many helps in decision already exist. Besides, the relationships between hydrology and hydroecology are quite important now. The recurrent difficulty to obtain a consensus in the final decision lies more in the fact that the objectives are often not clear, and that the social evolutions towards ecological concerns are not well accepted. The result is that scientists are usually asked to improve again the methods instead of having the right debate. Among different solutions, the most important one is to obtain the essential feedback experience in ecological studies, wilh an accurate quantification of the real evolution of the stream after application of predicted minimum flows. It is the only new step to be expected, and it is the only one to avoid other laws like the "loi relative à la pêche en eau douce" of 1984, often regarded as too arbitrary.