Water is Switzerland's most important natural resource. It is exploited for the production of electricity.

Power stations have been built along several of the major rivers, most notably the Rhine and some of its tributaries.

The construction of such dams has drastically reduced the flow of the water. They also hamper the migration of fish and other animals.

Power companies are well aware of the problem. When stations are modernised, efforts are made to provide natural banks as far as possible. Ladders are built for fish and other animals to bypass the obstacle.

Reservoir dams in the mountains have also had a negative impact on rivers. They release water from their turbines at different rates according to the demand for power, causing water levels downstream to fluctuate considerably. Fish and their eggs may be washed away, or stranded when the water falls again.