Answer:
Out of the given statements, the statement that best describes the impact of a dam on the environment is that it causes changes in the river ecosystem.
Step-by-step explanation:
- Dams are usually built on rivers that flow through valleys formed by two elevated landforms on two sides.
- Thus, when a dam is built, it interferes with the natural setting and stops the natural flow of the water.
- This makes the water levels behind the dam grow considerably. Many a times, the landforms in the surrounding regions get submerged in the water due to the increased levels of water.
- The natural movement of aquatic animals like fishes and crabs is also hindered by the dam.