How are dams created over perennial rivers?

Streams and rivers have to be diverted to create a dry area to construct the dam. Small rivers and streams are usually diverted through a tunnel, or a channel that is constructed around the side of the dam. Soft soils and rocks are excavated to form the route, while harder rocks have to be blasted with explosives. read more

A perennial stream or perennial river is a stream orriver (channel) that has continuous flow in parts of its stream bed all year round during years of normal rainfall. For most people, talking about a"perennial" river is redundant - as ALL the rivers and streams in their area are perennial rivers. read more

A weir (also sometimes called an overflow dam) is a type of small overflow dam that is often used within a river channel to create an impoundment lake for water abstraction purposes and which can also be used for flow measurement or retardation. read more