[NEW DELHI] Parts of India could face a severe water crisis due to the overexploitation of groundwater for irrigation and other human uses, new satellite data shows.
Scientists from the US-based National Aerospace and Space Administration's (NASA's) Goddard Space Flight Center studied satellite images of groundwater storage in three states in northwestern India — Rajasthan, Punjab and Haryana — from 2002 to 2008.
They found that groundwater levels are falling by four centimetres a year, and about 110 cubic kilometres of groundwater have been lost over the six-year study period, they report in Nature today (13 August).
If the current level of unsustainable over-consumption, mainly for agriculture, continues, India could face severe water shortages, they caution. They add that the reduction cannot be attributed to changes in climate.
"Groundwater is extremely valuable as a resource which stores water during the wet years and makes it available in the dry years, so that people and farmers can survive droughts, whether part of the natural variability or related to climate change. However, groundwater must be managed sustainably, or in time this capability could be lost," Matthew Rodell, a NASA hydrologist and lead author of the study, told SciDev.Net.
Rodell says 95 per cent of groundwater withdrawal from the region is for irrigation, mainly for rice, wheat and barley. "If farmers shift away from water intensive crops, such as rice, and also implement more efficient irrigation methods, that would help," he says.
He hopes his team's research will provide the data for the Indian government to carry forward proposals to regulate groundwater use.
The NASA data roughly tallies with estimates from India's ministry of water resources based on a simpler and cheaper method of drilling holes and measuring water levels four times in a year. This water level fluctuation method helps assess both how much rainwater is contributing to underground aquifers and reservoirs, and how much is being used.
A recent (25 June) report in Current Science by Rana Chatterjee and Raja Ram Purohit, senior hydrologists at India's Central Ground Water Board, reports overexploitation of groundwater in northwestern, western and peninsular India.
Chatterjee and Purohit estimate that Indians use 231 billion cubic metres of groundwater each year, 92 per cent of it for irrigation. Their detailed estimates, carried out by splitting the country into 5,723 500-square-hectare units, aimed to identify areas requiring immediate attention. They found that 839 are overexploited, most of them in northwestern India.
Nature doi 10.1038/nature08238 (2009)
Current Science 96, 1581 (2009)