Hint: A dam is a structure that prevents or restricts water or underground streams from flowing. Dams build reservoirs that not only prevent flooding, but also provide water for irrigation, human use, industrial use, aquaculture, and navigation.
A dam is a structure constructed across a river or stream to keep water from flowing downstream. Over the years, various materials have been used to build dams. Natural materials such as rocks and clay were used to build ancient dams. Concrete is frequently used by modern dam builders.
Large-scale degradation of natural vegetation and wildlife occurs as a result of the construction of a massive dam in areas that are submerged. This is bad for the environment. As a result, environmental considerations must be carefully considered prior to the construction of large dams.
Some environmental hazards of dams are:
- Dams, unless explicitly designed to allow fish to pass through them, provide a barrier for fish that need to migrate downstream and upstream along a river to spawn and reproduce.
- Flooding and habitat destruction: Dammed rivers build a reservoir upstream from the dam, which flows into the local area, flooding ecosystems and habitats.
- Since a dammed river can no longer flow freely, sediment that would have been deposited naturally downstream continues to accumulate behind the dam, creating new riverbanks, river deltas, alluvial fans, braided channels, oxbow lakes, levees, and coastal shores. Changes in sedimentation can cause significant changes in plant and animal life.
- Production of methyl-mercury: Stagnant water in lakes allows inorganic mercury to be converted to methyl-mercury through the decomposition of organic matter from rotting plants. Unfortunately, methyl-mercury has a tendency to bioaccumulate and cause toxic effects in humans and wildlife that consume reservoir fish.
Note: Some disadvantages of dams are:
- During building, people are displaced.
- Reservoirs release a significant amount of greenhouse gases.
- Local habitats are often disrupted.
- It wreaks havoc on the groundwater table.
- Water cannot flow to other nations, states, or areas.