Effects of Dams and Reservoirs On The Environment

Effects of Dams and Reservoirs On The Environment

First of all, what are dams and reservoirs?

Well according to Wikipedia:

"A dam is a barrier that impounds water or underground streams. Dams generally serve the primary purpose of retaining water, while other structures such as floodgates or levees (also known as dikes) are used to manage or prevent water flow into specific land regions. Hydropower and pumped-storage hydroelectricity are often used in conjunction with dams to generate electricity. A dam can also be used to collect water or for storage of water which can be evenly distributed between locations."


A dam usually look like this:

Building dams are for the benefits of the human community as it provides clean energy, water supply control flood and many more.

However nowadays the building of dams has caused quite a lot of concerns due to the increase awareness of negative environmental impacts of dam building.

So how does building dams and water reservoirs affect our environment?

1. It blocks fish migrations such as salmon, completely separating spawning habitats from rearing habitats.

2. Dams trap sediments, which are critical for maintaining physical processes and habitats downstream of the dam. This includes the maintenance of productive deltas, barrier islands, fertile floodplains and coastal wetlands which have important ecological functions to the environment and the animals.

3. Transformation upstream of the dam from a free-flowing river ecosystem to an artificial slack-water reservoir habitat. There will be major changes in temperature, chemical composition, dissolved oxygen levels and the physical properties of a reservoir which are often not suitable to the aquatic plants and animals that evolved with a given river system. 

4. Disrupting and altering water flows which could lead to rivers drying up. This will directly affect the chances of survival of the aquatic life (plants & animals) in the river down stream.

5. Water quality can be degraded. Reductions in water quantities can increase salinity and make the water unusable for drinking and irrigation. Decomposition of organic matter and the leaching of mercury from the soil can introduce toxins.

6. Reservoirs can emit climate-changing greenhouse gases. Particularly in tropical areas, the release of carbon dioxide (CO2) and methane as flooded trees and plants decompose is a serious cause for concern that needs more investigation.

However, not everything about dams and water reservoirs are negative.

Dams can be used to generate hydroelectricity which is a renewable source of energy. Also proper mitigation plans on the negative effects of dams towards the environment can be planned to reduce the negative effects on the environment. An example would be implementing habitat restoration for the wildlife.