Driving water under ground

22nd day of Aug 09

Nasa's twin GRACE satellites orbitting the earth in formation at a height of 300 miles and roughly 137 miles apart are tasked with an ambitious

mission: They track the world's freshwater reserves, including those hidden far from the naked eye under thick rock in vast underground aquifers spanning transnational boundaries. As Nasa scientist Mark Rodell and his colleagues trawled data on Punjab, Haryana and Rajasthan, states the Indian government accepts are affected by groundwater depletion, they discovered water was vanishing at the rate of 17.7 cubic km of water (+- 4.5 km) every year as against the official estimate of 13.2 cubic km. Clearly, estimates of replenishment or usage, or both, had been incorrectly calculated. According to GRACE, India's food bowl, with a paddy coverage of 38,061 sqkm, is losing groundwater at the rate of 1 metre every three years or a foot each year. The science behind the GRACE mission is fairly simple. The satellites map shifts in the gravitational pull of large underground water reservoirs, in this case the 560,000 km Indus River plain aquifer, straddling the India and Pakistan border, to check groundwater. The findings are quite undeniable but have been met with a surprising lack of official response in India, particularly to the argument that more than 90% of underground water is used for irrigation. What the satellites revealed ought not to be a surprise. Central groundwater board studies point to a worrying country-wide trend. Data relating to 2006 shows a staggering fall of 2 metres in several Andhra Pradesh and Karnataka districts in comparison to previous years. Tamil Nadu was worse with levels dropping by 2-4 metres. Water fluctuation in January 2007 in comparison to the average — between 1997-2006 — revealed more than 20% of monitoring wells in Punjab, Haryana, Chandigarh, Bihar, West Bengal, east Madhya Pradesh and east Rajasthan registered a decline of more than 2 metres. Only parts of UP and the hilly areas of the north registered improved groundwater use. The 2007 CGWB report states 18% of assessed units in Andhra Pradesh, 78% in Delhi, 49% in Haryana, 75% in Punjab, 59% in Rajasthan, 37% in Tamil Nadu, 14% in Gujarat and 12% in Uttarakhand are "over-exploited." Its projections of groundwater availability for irrigation in 2025 — not surprisingly — show negative figures for Haryana, Punjab and Rajasthan. Only in some areas, like the hilly terrain of West Bengal, Assam, parts of Meghalaya, Tripura and Jharkhand, there is rise in water levels by more than 2m as in the case in parts of the sub-Himalayas. But this year, with the drought now covering nearly 250 of the country's 500-odd districts, the stress on groundwater has increased manifold. Now, even in the hills of Uttarakhand and Himachal Pradesh, drinking water needs are being rationed through tankers. In Punjab, out of the 138 blocks, 103 have over exploited groundwater, five have reached critical levels and another four are nearing the red zone. The groundwater development in Punjab is 145% which means that water is being used at a rate of 45% more from underground sources than natural systems or artificial recharging can replenish. A planning commission report records number of critical blocks grew from four per cent in 1995 to 15 per cent in 2004. With crop productivity declining, there has been a shift to use of more and more fertilizers and pesticides requiring larger quantities of water. With the government planning to combat drought by sinking in hundreds of tubewells, the pressure on groundwater is bound to increase. As a hydrological cycle, groundwater replenishment sees a percentage of water that falls on the ground seeping through to fill underground aquifers. When a well or a diesel pump pulls out water it begins to deplete the water bank underneath. Normally rains and river water recharge the ground. But clearly, agriculture and drinking water is taking a serious toll. These signs have been visible in green revolution states for more than a decade now with the diesel costs running higher each year as pumps have to be sunk deeper. The crop boom in Haryana and Punjab helped achieve food security but this has come at an ecological cost even as sustaining agriculture became more difficult as productivity tapered off. The green states of the north are now witnessing a situation where extensive irrigation required is not adequately met by the surface water alone. A bad monsoon has only shown how close to the edge we live.