CHENNAI: Tamil Nadu is staring at an acute water shortage for agriculture. A draft report ‘Sustainable Land Use Policy’ prepared by the State Planning Commission has pegged the shortage of water for crops at 4,646 tmcft (thousand million cubic feet) by 2050, which is equivalent to nearly 50 times the storage capacity of the Mettur dam.
This means that agriculture, which accounts for 13% of the state economy, may have to undergo a perceptible change in terms of crops, land use, use of water, and productivity. The report has asked the government to encourage cultivation practices such as off-season tillage, the system of rice intensification, the sustainable sugarcane initiative, crop substitution, and micro-irrigation techniques.
What is more worrying is that the state is facing an unprecedented groundwater pollution due to industrial effluents. Accessibility to potable water has become a huge concern in several areas. Industrial regions such as Chennai-Manali, Vellore, Vanniyambadi, Thoothukudi, and Tirupur are facing an acute water pollution threat.
Being one of the most water-deficient states, TN has a low per-capita availability of 900 cubic metres of water annually as compared to the national average of 1,486 cubic metres, says the report. As of now, TN’s total water demand — for domestic, irrigation, livestock, and industrial needs — stands at 1,867.85 tmcft a year, while the total availability of all water resources is only 1,681.78 tmcft.
According to the report, the state’s water deficit is more of a structural one than a seasonal one. TN has 17 river basins, of which Cauvery is the only major basin, whereas 13 are medium and three are minor river basins. About 40% of the land mass of TN has overexploited underground water status.
More than 95% of surface water and 80% of ground water are already in use.Some districts, even in the Cauvery region, show the highest relative decline in groundwater, while a few other districts face the threat of moving towards the critical category. This has enormous implications for agriculture. It is also going to impact domestic needs as well as water-intensive industries. The report has insisted that the land available for water conservation should be maintained and protected from the growing threat of conversion into other land use purposes.
“The supply-demand gap will continue to increase if the government does not look at the issue in a different way,” says Prof S Janakrajan, president, South Asia Consortium for Interdisciplinary Water Resources Studies. “Though the rainfall pattern has changed, the state has yet to look at rainfall accounting, water budgeting, and water accounting. This could help in providing crucial data on how much rainwater is being utilised by the state while how much is let into the sea,” he says
According to the report, there is a decline in the area irrigated by canals and tanks, which has, in turn, led to a rise in the area irrigated by wells. The extreme dependency on groundwater is likely to reduce its availability further and increase the cost of water extraction. Declining ground water tables, encroachment of irrigation channels, decline of community involvement in maintenance of irrigation structures, water disputes, soil erosion, and excessive use of chemicals are some of the critical issues faced by the TN’s agriculture sector.