| چکیده انگلیسی مقاله |
India with a total area of 3,287,263 km2 is situated in the monsoon climate zone of south Asia. The country is divided into 28 states and 9 :union: territories. Rainfall from the southwest monsoon is the main source of fresh water in India. The country receives almost 80-90% of its annual rainfall during the southwest monsoon season from June to September. Since most of the fresh water in India occurs during 4 months in a year, whereas the country needs water throughout the year for domestic use (including drinking water), irrigation, industry, production of hydro electricity and a host of other purposes. Therefore, there is a need for the conservation of the monsoonal rainwater through the construction of dams across the Indian rivers for its use throughout the year. The main principle guiding the water conservation has been to ensure adequate supply of water for various uses as described above. The average annual flow in India’s river systems is 1869 km3 (BCM) which gives per capita water availability of 1902 m3.yr-1. Today world per capita use of water is 710 m3.yr-1. According to the ford foundation team India has one of the largest supplies of water in the world. It is estimated that out of 1869 km3 water only about 690 km3 water can actually be stored because of the geographical factors, especially the location of proper sites, climate and soil conditions. There were only 250 storage dams in the country at the time of India’s independence in 1947 with total water storage of about 12 km3 (BCM). The need for increasing dams for more water conservation was felt after 1947. As a result India exhibited great engineering feats in the construction of a large number of dams in the different states of the country for the conservation of the monsoonal rainwater to meeting water needs of the growing population. Consequently, there has been a rise in the number of dams and up to the end of the year 1990 there were about 3634 dams in India (CWC, 1990). Out of these about 2154 dams are large each having storage of more than 60 million m3 water. These dams provide water supply for domestic use, agriculture, industry, power generation also for flood control works. The storage build up in the completed dams was about 254 km3 (BCM). This indicates that about 36% of the estimated usable water resource or 14% of average annual flow in the rivers was being stored up to the end of the year 1990. While the situation has improved from 250 dams in 1947 but there is a great scope for more rainwater conservation through dams. India proposes to continue with its program of dam construction to create additional storage of 200 km3 to ensure continued sufficiency in food grain production and to meet the energy and drinking water needs of a growing population. In this paper, we review realistic situation as to what proportion of the available rainwater in each state of India is presently being conserved through their dams. |
