https://phys.org/news/2018-11-problems-win-win-solutions.html

In some parts of the world, there are proposals to build thousands of massive new dams for hydroelectricity, flood control and irrigation. In other regions, such as the U.S., there is a growing movement to restore rivers by removing dams that are obsolete, pose safety risks or have large negative impacts on ecosystems. In both instances, difficult trade-offs and divergent stakeholder preferences can greatly complicate decision-making processes.

For example, conservation groups and resource agencies seeking to restore sea-run fish often favor the removal of dams that prevent these species from reaching their spawning grounds. But other stakeholders may value the diverse services that dams can provide, including water supply, hydroelectricity and reservoir-related recreation.