Dams in India have been built across many perennial rivers, as a part of several multi-purpose projects to serve a variety of needs. Basically, dams are built to harness the river water so that it can be utilised according to the needs. The aim of a multipurpose project is storing water for irrigation purposes, generating hydro-electricity by utilising the water stored by the dams, preventing floods and facilitating afforestation in the catchments areas of the reservoirs. Moreover, the dams also provide drinking water, using the canals for navigation in some areas and also facilitating Pisciculture and recreational activities. The main multipurpose projects constituting Indian dams are the Hirakud Dam in Orissa, the Bhakra-Nangal Project in Punjab, the Damodar Valley Project in Bihar and West Bengal, the Tungabhadra Project in Andhra Pradesh and Karnataka, the Rihand Project in Uttar Pradesh.

Some of the most efficient Dams in India are Nagarjuna Sagar Dam, Prakasham Barrage, Somasila, Koil sagar Dam, Ranganadi Dam, Salaulim Dam, Sukhi Dam , Pong Dam Reservoir, Ranjeet Sagar Dam, Salal Hydroelectric Project , Bursar Dam, Maithon Dam, Linganamakki Dam, Chakra Dam , Mattupetty Dam, Bansagar Dam, Khuga Dam, Tansa, Isapur Dam, Balimela Reservoir, Jawahar Sagar Dam, Rangit Dam, Kallanai Anaicut, Vaigai Dam, Ramganga Dam, Tehri Dam, Farakka Barrage etc.

Construction of Dams in India
The construction process of Dams are rather multifarious and prolonged, which requires high level of technical expertise, along with suitability of various natural factors. One particular determinant of construction of dams in India is topographic suitability. River gradient strongly influences the location of dams. Like for instance, a river flowing at comparative positive gradient usually favours irrigation dams; while elevated water levels upstream aid water storage and distraction into irrigation canals. As a result, new dams are likely to be constructed in those areas, which have river flowing at a modest incline. After one accounts for the impact of the overall higher altitude of the district and the availability of rivers, the gradient of the rivers is unlikely to have a direct impact on changes in agricultural productivity or other district-level outcomes before and after a state builds new dams. Therefore, it is advised to use the variation in dam construction induced by differences in river gradient across districts within Indian states to determine the impact of large dams.

Construction of large dams has always been a significant and costly undertaking of the Government of India. The case of large dams recommends strongly that distributional implications of public polices should be integral to any decision.

Development of Dams in India
Punjab, Haryana and Rajasthan have jointly launched the Bhakra-Nangal Project. It is the biggest Multi-Purpose River Valley Project in India, started in 1948 and completed in 1968. This project derives its name from the two dams Bhakra and Sutlej, built on a tributary of the Indus River, the Sutlej River. Hirakud Dam Project is the first chief multi-use river valley project in India, after its independence. Constructed across Mahanadi River at about 15 km upstream of Sambalpur town in Orissa the main dam, the Hirakud is 6 kms from National Highway 6.

The Rihand project is one of the most significant multi-purpose projects in the state of Uttar Pradesh. Rihand River flows across a narrow gorge in the Vindhyan mountain ranges in the Mirzapur district of Uttar Pradesh. Tungabhadra project is a combined undertaking of the states of Karnataka and Andhra Pradesh. This dam is 2441 m in length and 49.38 m in height. It is built on Tungabhadra River at Mullapuram (in Bellary district about 4.8 km from Hospet. An important feature of Tungabhadra project is the 11.6 m high and 692 meters long barrage built across Damodar at Durgapur.

Other dams include, Polavaram Dam, Somasila, Singur Dam, Ranganadi Dam, Hasdeo Bango Dam, Dudhwa Dam, Salaulim Dam, Kakrapar Dam, Ukai Dam, Chamera Dam, Ranjeet Sagar Dam, Bursar Dam, Sawalkot Dam, Palna Dam, Tilaiya Dam, Kadra Dam, Linganmakki Dam, Chikahole Dam, Taraka Reservoir, Chakra Dam, Vazhani dam, Pothundi Dam, Bansagar Dam, Loktak, Kolkewadi Dam, Temghar, Farakka Barrage and many others.

Advantages of Dams in India
In the year 1947, there were around 300 large dams throughout the country and number gradually increased by the year 2000, when it reached to almost 4000. India holds a strong position in the list of dam building countries, after US and China. Primarily some of the dams in India were constructed for the prevention of floods, supplying water for irrigation and generation of electricity. Dam construction is considered as one of the greatest investments in the field of irrigation. Most irrigation dams in India are embankment dams, meaning that they consist of a wall built across a river valley to impound water so as to form a reservoir upstream and a system of spillways and gates to bypass the wall so as to maintain normal river flow and convey water to a network of canals feeding irrigated regions downstream.

The upstream areas that feed the dam and those submerged by its reservoir are called its Catchments area, and the downstream areas fed by its irrigation canals and are known as the Command area. Owing to the construction of dams in India, the country`s food grain production increased rapidly over the past few decades. As a result importation rate has also increased tremendously.

Disadvantages of Dams in India
However, there are also certain disadvantages of dams in India. Large-scale confiscation of water raises contact to several vector-borne diseases, like filarial, malaria, schistosomiasis and river blindness.

The dams of India have developed the internal navigation by which the pressure on the railways has relieved to some extent. Moreover, these dams have effectively controlled floods on rivers, thus preventing untold damage to the people of the nation.