Hydropower and good health of aquatic ecosystems: from current to future innovative solutions

As an intersection between environmental (e.g. ecological continuity restoration) and societal (e.g. flexible source of energy) needs, the development of sustainable hydropower is a great challenge. In this context, the issue is to find out solutions allowing hydropower energy to be as “green” and sustainable as possible. Hydropower is obviously not the only source of disturbance in environmental/ecological processes, but it may have an impact by various ways: i) the transport of sediment toward downstream sections is reduced, which may subsequently produce morphological alterations, ii) small and large dams induce physical barriers for upstream and downstream fish migrations, iii) these barriers create upstream reservoirs that can swamp habitats such as spawning grounds, iv) the passage through turbines can injure fish or induce mortality, v) modifications of river discharges and regimes may alter the availability and quality of downstream habitats, vi) chemical and thermal qualities of water can be altered, especially in huge reservoirs, vii) cumulative impacts are observed. The picture seems dark, but there actually are various solutions (and perspectives) to mitigate hydropower effects on aquatic ecosystems. To propose effective solutions, it is important to develop a certain "way of working", considering the regulatory framework and operational needs, in order to product and transfer adapted methods and tools. To manage this, interactions between the different stakeholders should be as great as the challenge