It is a renewable or inexhaustible resource.
It is pollution-free.
However, this source of energy has two major drawbacks.
Firstly, it calls for huge financial lay out particularly in those regions where water is to be impounded in huge quantity to ensure free flow of water all the year round.
Secondly, in most cases its gestation period is too long.
With the water power potential of 41000mw, India ranks fifth in world after congo, Russia, Canada and the U.S.A.
Development of hydroelectric power started in the last decade of the 19th century with the establishment of a hydroelectric plant for supplying electricity to Darjeeling in 1897.
In 1902, another hydro power plant was erected at Sivasamundram water fall on Kaveri river in Karnataka.
Total installed capacity of hydroelectricity increased to 25, 219.55 MW at the end of 2000-01, which was nearly one-fourth of the total installed capacity, of electricity.
In spite of being cheaper, pollution-free and renewable source of power, significance of hydroelectricity has declined in post-independence period.
Its share in total power generation declined from 49 percent in 1950-51 to only 14.9 percent in 2000-01.
Nevertheless, hydroelectricity plays a very significant role in northern, western and southern grids.
The Northeastern grid is primarily dependent on hydel power.
In context of the energy crisis in the country hydroelectric power has assumed pivotal significance.
Indian rivers drain 1677 billion cubic metres of water to the sea every year.
The Central Water and Power Commission estimated the potential of hydroelectric power at about 40 million kW at 60% load factor from these rivers.
Central Electricity Authority re-estimated this potential at 84,000 MW at 60% load factor.
It is equivalent to about 450 billion units of annual energy generation.
The rivers originating from the northern mountainous region are the most important ones in this respect.
They have their sources in glaciers and snowfields, therefore, they are perennial and their flow of water is regular throughout the year.
Velocity of flow is high because of dissected terrain and the competition for use of water for other purposes is low.
The northeastern part of this mountainous region, constituting the Brahmaputra basin, has the largest power generating potential.
The Indus basin in the northwest is at second place.
The Himalayan tributaries of the Ganga have a potential of 11,000 MW.
Thus, three-fourths of the total potential is confined in the river basins originating from the northern mountainous region.
The rivers of peninsular India are comparatively poor in this respect.
They depend entirely on the rainfall for their flow, and therefore, their flow is very erratic exceptionally high flow during the monsoon period fol1owed by a long period of lean flow.
Storage of water is essential to regulate the flow.
The bulk of the potential in this part is confined in the hilly regions along the middle and upper reaches of various river systems.
The Western Ghats, Northwestern Karnataka, Nilgiri and Anamalai hills and upper Narmada basin are major areas of concentration of potential in peninsular India.
Despite this, potential of hydro power has been comparatively more developed in southern states because these states are far away from coalfields of the northeastern plateaus.
Hydro electricity dominated region
The states included under this category are Karnataka, Kerala, Himachal Pradesh, Uttarakhand, Jammu and Kashmir, Meghalaya, Nagaland, Tripura, and sikkim.