Northern India Rapidly Depleting its Groundwater Due to Excessive Irrigation; Major Water Crisis Looms If Trend Continues
Northern India, probably the most heavily irrigated region in the world, is rapidly depleting its groundwater, according to a new study by researchers from the National Geophysical Research Institute, Hyderabad (CSIR), India; the University of Colorado, Boulder; and the US National Center for Atmospheric Research. If sustained, the trend will lead to a major water crisis in the region, the researchers conclude in a paper to be published in the AGU journal Geophysical Research Letters.
Combining gravity observations recorded by the GRACE satellite missions with hydrological models to remove natural variability, the team concluded that the region lost groundwater at a rate of 54 ± 9 km3/yr between April, 2002 (the start of the GRACE mission) and June, 2008.
The results for the period suggest a total groundwater extraction rate of about 70% larger than estimates for the mid-1990s. “This dramatic increase shows the dynamic nature of this increasingly critical situation,” they write in their paper. Northern India and its surroundings are home to roughly 600 million people.
This is probably the largest rate of groundwater loss in any comparable-sized region on Earth. Its likely contribution to sea level rise is roughly equivalent to that from melting Alaskan glaciers. This trend, if sustained, will lead to a major water crisis in this region when this non-renewable resource is exhausted.
...The region where GRACE shows decreasing groundwater storage has among the world’s highest population densities. The demand for agricultural products is intense. Groundwater demand is expected to grow many fold in coming years, with increasing agricultural growth and industrialization. Although future climate change is expected to intensify the precipitation and thus increase water availability in this region, evaporation will likely also increase due to the warmer climate. It could thus well be that one of the most populated areas on Earth will eventually be struggling for water. It is of immediate concern to recharge the aquifers of north India, Nepal and Bangladesh through suitable management of surface water for the sustainable availability of water and the preservation of ecosystems.—Tiwari et al.
GRACE provides monthly, global, gravity field solutions at scales of a few hundred km and greater, in the form of spherical harmonic coefficients. Models remove atmospheric and oceanic contributions. The researchers computed monthly mass changes in southern Asia, which they interpreted in terms of changes in continental water storage.
The gravity field results are equally sensitive to water at all depths: surface water, soil moisture, and groundwater, and include anthropogenic effects. To isolate the anthropogenic contributions, they subtracted monthly water storage estimates predicted by land surface models.
V. M. Tiwari , J. Wahr and S. Swenson (2009) Dwindling groundwater resources in northern India, from satellite gravity observations. Geophys. Res. Lett., doi: 10.1029/2009GL039401, in press