India is facing a dire need for greater and more efficient water storage, without which the country’s grossly insufficient storage capacity amplifies the effect of rainfall deficits, and exacerbates drought conditions. On the one hand, per capita availability of fresh water has declined sharply from 3,000 cubic metres to 1,123 cubic metres over the past 50 years, while the global average hovers at around 6,000 cubic metres. Simultaneously, each year India is estimated to lose the approximately two-thirds of the new water storage capacity to excessive siltation and improperly managed runoff. Between 1992 and 2004, for example, 200 large and medium-sized irrigation works were constructed yet the area irrigated by such schemes shrank by 3.2mn hectares. Unless sizeable investments are undertaken to de-silt reservoirs and repair damaged canals, dams and irrigation works some estimate that by 2050 India may well run short of water. The fourth installment of a six-part series examines the problems of water storage and surplus management in the Mettur Dam catchment area in Tamil Nadu.
Anbu, a businessman, from Govindappadi village near the majestic Mettur dam, is one of many residents caught in what seems to be an unusual predicament. “Our villages, despite proximity to the Cauvery, face acute drinking water scarcity,” he says, adding, “It is no better than the drought prone areas of Krishnagiri and Dharmapuri districts.”
His story is not uncommon to this area. The Mettur dam may be the lifeline of the Cauvery delta supplying drinking water to almost one-third of the population of the state, but for villages surrounding the structure water scarcity is an everyday reality. Irrigation has also been compromised in the proximity of what should in theory be a water- zone, and after fighting for over four decades to divert the dam’s water to water bodies in the district farmers in delta are ready to throw in the towel.
N. Perumal, State General Secretary of the Tamil Maanila Congress Vivasaya Sangam is cynical. He says that despite receiving excess rainfall during the months of November-December, the rural areas of Salem district are bracing for an acute water crisis with Mettur Dam and other water bodies drying up fast. “The farm activities in about 45,000 acres in Salem, Namakkal and Erode districts under the Mettur dam’s East-West Canal scheme is undertaken with much difficulty every year,” he says, with a resigned air.
Frustrated by the constant wastage of surplus water released through 16-vent Ellis Saddle surplus channel, office-bearers of the Cauvery Surplus Water Action Committee complain, “It is painful to see surplus water flowing into the sea without benefiting anyone.”
If supply is this erratic during times of relative comfort, then how severe would water scarcity be when drought-like conditions grip the region?
Wasting precious water
Even though parts of Tamil Nadu have escaped the burning heat and dry conditions of North India, such as what the Marathwada region in Maharashtra is witnessing, the efficiency of water storage here inspires neither confidence nor hope.
The Mettur dam has "surplussed" more than 40 times in its 82 years of existence. Surplussing occurs during the southwest monsoon when five to 80 thousand million cubic feet (tmcft) of water drains in to the sea, while 70 per cent of lakes in Salem remain dry.
Despite such surplussing, on Thursday the water level in the Mettur dam had dropped to an alarming 50.10 feet against its total capacity of 120 feet. While the inflow was only 44 cubic feet per second (cusec) 2,000 cusecs had to be discharged to supply drinking water to the delta districts. Even worse, it would appear that the discharge is not being taken up efficiently, either for drinking water or for irrigation. Instead it ends up as run-off, which is water that is wasted rather than channelled for any useful purpose.
On multiple occasions the farming community here demanded that the government harvest surplus water released from Mettur dam to fill water bodies in Salem, Namakkal and Erode. If the authorities had complied, the water-laden tanks, ponds and reservoirs in the area would have recharged the groundwater. They have not.
Silt accumulation
Besides poor water management owing to ineffective systems for tapping the run-off of surplus water, the accumulation of silt has been a serious obstacle to attaining full storage potential at the Stanley reservoir in Mettur. The Reservoir was constructed in 1934. Yet it has not been desilted even once. Such negligence has resulted in a situation where the Mettur dam has been losing on an average 0.4 per cent of its holding capacity due to silt and sand every year, according to A. Mohanakrishnan, former Advisor to State Government on Water Resources.
Today the dam’s actual capacity stands at only about 65 tmcft, down from its total capacity of 93.47 tm, with silt accumulation accounting for 20 per cent of the storage capacity of the dam.
Unless there is a major intervention in the water storage ecosystem of this region, residents such as Anbu and Perumal will continue to be water-poor in potentially one of the most water-rich regions of the state.
