Although dams serve many important purposes, they can also have a negative impact on the environment by

Negative impact on the environment by dams:

We all know that dams are important where there is heavy flow of water. Dams also have negative impact which are numerous and varied. They create impact on biological, chemical and physical properties. When dams are built across the river, fish migrations are affected. They also trap the sediments which affects the physical processes.  

The temperature changes, composition of chemicals and the dissolved oxygen levels are not suitable for aquatic plants and animals. Due to the downstream of riverbed in dams it may affect more than 100 kilometers below a dam.

Thus, we can conclude that construction of dams can affect aquatic species, loss of forest, wetland and farmland and extinction of birds in the floodplains.