Dam

A dam is a physical obstruction constructed across a river to store the water in reservoir and divert it for multipurpose from its upstream side.

The pool of water form on the upstream side of the dam, is called as the reservoir of the dam. 

Purpose

1. Irrigation

The primary and main purpose of constructing a dam is to store water and use it for irrigation. The World Commission of Dam estimates around 30-40% of irrigated land relies on dams. It is estimated that 60% of the food production that comes to the market is dependent on dam water for their irrigation.

The major irrigation projects, which are dependent on the dam, often help prevent the mitigation of rural people to the cities, while giving them a higher standard of living in their native areas.

2. Hydropower Generation

Hydropower is considered the largest renewable energy source of electricity and clean because it does not contribute to global warming, air pollution, acid rain, or ozone depletion.

Hydropower generated by the dams is the most plentiful and most efficient renewable energy resource, contributing to 24% of all renewable electric energy produced all over the world. The Itapúa Dam on the Parana River in South America generates 14 GW and supplied 93% of the energy consumed by Paraguay and 20% of that consumed by Brazil as of 2005.

3. Flood Prevention

Flood control is a significant purpose for many of the existing dams and continues as the main purpose for some of the major dams of the world currently under construction. The dams are used to effectively regulate the level of water flowing in the river by temporarily storing the flood volume and releasing it later. Every dam has an integrated water management plan for regulating the storage and discharge of water into the river basin without damage. This plan helps to impound floodwaters and then either release them under control to the river below the dam or store or divert the water for other uses. This strategy eliminates flooding which prevents the loss of life and property.

4. Water Supply

Dams play an important role in the water supply for domestic and industrial use. Dams store the water and supply it during the shortage of times.

The major percentage of rainfall precipitates on the ocean and the rainfall on the earth is wasted as runoff, a mere 2% of infiltrated to replenish the groundwater. So properly planned and designed dams can store contribute significantly toward fulfilling our water supply requirements.

5. Inland Navigation

Dams just not only serve as an irrigational lifeline, but also provide inland navigation throughout the heartland of the nation. The advantages of inland navigation, however, when compared with highway and rail are the large load-carrying capacity of each barge, the ability to handle cargo with large-dimensions and fuel savings.

Enhanced inland navigation is a result of comprehensive basin planning and development utilizing dams, locks, and reservoirs which are regulated to provide a vital role in realizing regional and national economic benefits.

6. Recreation

Dams provide prime recreational facilities such as boating, skiing, camping, picnic areas, and boat launch facilities are all supported by dams. The large water stored due to the construction of dams facilitates the growth of flora and fauna in the region due to which many recreational activities such as natural history, bird watching, landscape painting, walking, and hiking are on the rise.

7. Mine Tailing

A mine tailing dam is usually constructed by earth-filled embankment for the purpose of storing byproducts of mining operations. Tailings can be liquid, solid, or a slurry of fine particles, and are usually highly toxic and potentially radioactive.

The mines of copper, coal, gold, and uranium produce many kinds of waste, much of it toxic by-products which pose varied challenges for long-term containment of the environment. To mitigate this challenge, tailing dams are constructed to contain the effects of these harmful by-products.

8. Other Purposes

The purposes of dams are grouped into two categories, single-purpose and multipurpose. But maximum dams constructed are of multipurpose having one major purpose such as hydropower generation or irrigation and secondary purpose as recreation, flood control, waste management, river navigation, and wildlife habitat.

Structure Of Dam

Heel: contact with the ground on the upstream side

Toe: contact on the downstream side

Abutment: Sides of the valley on which the structure of the dam rest

Galleries: small rooms like structure left within the dam for checking operations.

Diversion tunnel: Tunnels are constructed for diverting water before the construction of dam. 

This helps in keeping the river bed dry.

Spillways: It is the arrangement near the top to release the excess water of the reservoir to downstream side

Sluice way: An opening in the dam near the ground level, which is used to clear the silt accumulation in the reservoir side.