Unstable Waters: Tamil Nadu

Tamil Nadu is a water scarce area and rain water is the major source of water supply in the state. Tamil Nadu accounts for 4 per cent of the land area and 6 per cent of the population, but only 3 per cent of the water resources of the country. Most of Tamil Nadu is located in the rain shadow region of the Western Ghats and hence receives limited rainfall from the south-west monsoon. The total water potential of the State is 36 km3 or 24,864 M cum. There are 17 major river basins in the State with 61 reservoirs and about 41,948 tanks. Of the annual water potential of 46,540 million cubic metres (MCM), surface flows account for about half. Most of the surface water has already been tapped, primarily for irrigation which is the largest user. There are about 24 lakh hectares irrigated by surface water through major, medium and minor schemes. The utilisation of surface water for irrigation is about 90 percent. The utilisable groundwater recharge is 22,423 MCM. The current level of utilisation expressed as net ground water draft of 13,558 MCM is about 60 percent of the available recharge, while 8,875 MCM (40 percent) is the balance available for use. Over the last five years, the percentage of safe blocks has declined from 35.6 per cent to 25.2 percent while the semi-critical blocks have gone up by a similar percentage. There is shortage of water for various competing requirements such as, domestic, agricultural, commercial and industrial purposes. Moreover, over the years, proper attention has not been given to maintain the sources of water storage built in the past, viz., lakes, ponds and tanks (including the Temple tanks), which criss cross all over the State, besides the naturally formed lakes and estuaries. Over the years, a large number of the water bodies have been encroached by anti-social elements. Temple tanks all over the State are invariably occupied by encroachers. Moreover, most of the lakes, tanks and ponds have remained unattended for long and as a result, silt formation has reduced their storage capacities. Above all, unscientific (mostly illegal) sand mining has caused severe damage to most of the river systems in the State. As there is growing pressure on available water resources due to the burgeoning demand for water, concrete steps have to be initiated to desilt, renovate and restore the existing water bodies and create new sources to increase water storage facilities so as to enable adequate supply of water. For providing equitable, affordable piped water supply to the people of the State it is required to explore and tap all obtainable sources of water, including rain water, groundwater, surface sources, desalination and waste-water re-use.