Dams are particularly controversial due to its negative environmental implications particularly those related to land erosion and aquatic species extinction. According to International Rivers, there are two main categories of environmental impacts associated with dam construction: those inherent to dam construction and those caused by operational features in each dam (McCully, 2001).
Examples of these are:
Impacts due to existence of the dam: upstream change from river valley to reservoir, changes in downstream morphology, changes in water quality, and reduction of biodiversity because of blocking of movement.
Impacts due dam's operation: changes in downstream hydrology (E.g.: total flows, seasonal timing), changes in downstream morphology, changes in quality, and reduction of riparian habitat diversity because of flood elimination.