Difference Between Dam and Reservoir

Dam vs Reservoir

Dam and reservoir are two interconnected terms. Since ancient times, mankind has been involved in a constant struggle to harness the water of flowing rivers so as to be able to supply the right amount of water to right places. The most popular means of achieving this endeavor is to create dams across rivers to control the flow of rivers and also to store water for various purposes. Thus a dam can be described as a man made barrier that is placed in between a flowing river to use its water in desired manner such as preventing excess flow in specific regions and making it flow to regions where there is a deficit of water. Reservoir is a term that in always used in connection with dams. It refers to the water body, more commonly called a lake that is created by the high walls of a dam. The major purpose of a reservoir is to store water but it is also used for many more purposes.

Today, nearly all major river systems in the world have dams built across them. This is done for economic and social development of the inhabited areas near these rivers. Dams are hard to build as they require heavy infrastructure and huge amounts of money. Dams bring along many benefits to us, but they also have detrimental effects such as displacing people living in nearby areas. There are also ecological disturbances but creation of dams has become a necessity in modern times. Sometimes a series of dams is built across a river system called a cascade of dams, to maximize benefits accruing through these dams. However, they can result in calamities to human beings and also adversely affect the biodiversity of the river system.

The major advantages of dams are in flood control, hydropower electricity generation, agriculture and in water transfers to areas with deficit of water. They are also used for domestic water supply. They make a river navigable by slowing down the flow of water.

Though a dam is not just a concrete structure and a reservoir is an integral part of a dam, people mistakenly consider the high concrete wall created to control the passage of water as a dam. Reservoir is technically impounding of water behind a dam. These reservoirs can be very large or like small lakes. There are two water levels, the high level and the low level. The difference between these two water levels of a reservoir is termed as drawdown zone which when multiplied by the area of reservoir gives the usable volume of water. This is the volume of water available for power generation and other purposes such as irrigation or domestic water supply.