Not poor rainfall but over-use of water behind drought, say NASA scientists
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Amounts of rainfall have not changed, but water use has. Four north Indian states -- Punjab, Rajasthan, Haryana and Delhi -- are using up 30% more of their groundwater resources than has been estimated by the Indian government, says a new NASA report
About a quarter of India is experiencing drought conditions, with a weak and delayed monsoon this year. However, says a US National Aeronautical and Space Administration (NASA) study, weather and climatic factors are not responsible for water depletion in the northwestern states of Rajasthan, Haryana and Punjab.
The study, carried out by a team of NASA scientists, is published in the latest online edition of Nature, a peer-reviewed scientific journal. The findings come within days of an Indian government report warning of a potential water crisis in the country this year.
Union Finance Minister Pranab Mukherjee said on August 11 that 161 out of 604 districts were experiencing drought because of a deficient monsoon, decreasing sowing by 20% in the ongoing crop season. Finance Secretary Ashok Chawla said states were being asked to submit reports of losses brought on by poor rainfall for the Centre to take necessary steps to avoid its adverse impact on economic growth.
Meanwhile, the Indian Meteorological Department (IMD) has revised its monsoon forecast to 87% of the long-period average (LPA) in the June-September season.
“We looked at the rainfall record and, during this decade, it’s relatively steady -- there have been some up and down years but generally there’s no drought situation, there’s no major trend in rainfall,” Matt Rodell, a hydrologist at NASA’s Goddard Space Flight Centre near Washington DC, said. “So naturally we would expect the groundwater level to stay where it is unless there is an excessive stress due to people pumping out too much water, which is what we believe is happening.”
The scientists used satellite imagery from the Gravity Recovery and Climate Experiment, or GRACE, a pair of satellites launched by the space agency in 2002. The mission can measure groundwater depletion because the amount of water in aquifers has a small gravitational attraction for the satellites.
Three years ago, GRACE scientists noted loss of water in parts of Africa. But the Indian result is more striking. “Over the six-year timeframe of this study, about 109 cubic kilometres of water were depleted from this region -- more than double the capacity of India’s largest reservoir is gone between 2002 and 2008,” Dr Rodell told the BBC.
While only 58% of India’s groundwater is recharged every year, Rajasthan, Punjab and Haryana are the only three states digging beyond the dynamic zone for groundwater. The scientists report that these states depleted, on average, 17.7 billion cu m (bcm) of water annually, between August 2002 and October 2008, more than the government’s estimate of 13.2 bcm in the same period. They conclude that groundwater depletion in the region was equivalent to a net irreplaceable loss of 109 bcm, or nearly 20% of India’s annual water consumption of 634 bcm.
The study warns that northern parts of India are on track for severe water shortages, with the water table falling by about 4 cm (1.6 inches) per year in the region that includes Delhi. The four states account for almost 114 million people, or almost 10% of the country’s population, and are dependent largely on irrigation for farming. Across India, groundwater accounts for around 50-80% of domestic water used, and 45-50% of water used for irrigation.
“The study clearly says there’s a plus/minus 4.5 bcm error in the estimate. So on the lower side that’s close to our estimate,” claimed B N Jha, chairman of the Central Groundwater Board which monitors groundwater levels in the country using a reliable method of measuring water levels in a national network of 15,000 wells. “When you take satellite measurements over such a large area, as opposed to physical measurements, there are bound to be errors,” he added.
According to the Planning Commission, irrigation consumes 83% of the country’s annual water budget. Northwest India is heavily irrigated and the government’s ‘State of the Environment Report’, published earlier this week, noted that irrigation increased rice yields seven-fold in some regions compared to rain-fed fields.
Dr Raj Gupta, a scientist working for the International Maize and Wheat Improvement Centre (CIMMYT), said that the current drought would lead to more groundwater extraction. “Farmers receive no rains so they are pumping a lot more water than the government expected, so the water table will fall further.”
He noted that some farmers might be able to switch from rice to crops that demand less water such as maize or sorghum. But, he said, that would depend on government policy (which has traditionally promoted rice) and on market demand.
“This issue is of grave importance,” said K Sreelakshmi, a natural resource economist at New Delhi’s Energy and Resources Institute, TERI. Sreelakshmi, who was not connected to the study, noted that previous research projects had revealed the dropping of groundwater levels, though this one had employed a new approach by relying on satellite data. “The question is, what do we do about the problem,” she said. “How do we recharge India’s dropping water table?”
Ashok Jaitly, director of water resources policy at TERI, said: “How do you reduce inefficiency when you don’t price water? Water has a long-term economic value that needs to be recognised.” In the agricultural heartland state of Punjab, for example, farmers are given free electricity so they can run pumps to bring up groundwater for irrigation; little is done to encourage them to adopt more expensive but sustainable techniques like drip irrigation. Elsewhere too water is heavily subsidised, if not free. “The whole policy framework is encouraging water-intensive farming,” Jaitly said.
The north Indian region has seen an enormous increase in water use since the 1960s. Part of that is because of growing populations, though a lot is due to the Green Revolution which dramatically increased India’s agricultural production -- in part by exponentially expanding the use of groundwater for irrigation.
Another recent study based on GRACE data, using results from a 2,000 km stretch across eastern Pakistan, northern India and Bangladesh, showed about 54 cubic km of groundwater lost per year. “Severe groundwater depletion is occurring as a result of human consumption,” the researchers concluded in the study.
“This is probably the largest rate of groundwater loss in any comparable-sized region on earth,” that study said. “As in other nations composed of smaller sovereignties and encompassing competing interests that have become dependent on a certain level of water availability, it is difficult to implement a coordinated and appropriately stringent response,” it concluded.
Source: http://news.bbc.co.uk, August 2009
The Financial Times, August 13, 2009
http://www.livemint.com, August 2009