Wednesday, April 21, 2010

Irrigation interfering with monsoons, says study

M Virat in Agricultural intensification and irrigation may decrease the Indian monsoon rains over the long term, a Purdue University and Indian Space Research Organisation study has found — suggesting regional land surface feedbacks play an important role in climate change.

The study analysed Indian Meteorological Department rainfall data of more than 50 years and tracked land use change using satellite imagery. Using a set of statistical tools, the researchers attempted to co-relate and then causally relate the data.

While the average rainfall over the whole of India remained stable, the study found a drastic change over north-western India where average seasonal rainfall has decreased by 35–40 per cent. The largest region with a negative trend in rainfall included portions in the states of Punjab, Haryana and western Uttar Pradesh — which benefited from India's Green Revolution when foodgrain production increased in the 1960s with adoption of high-yielding varieties, fertilisers and pesticides.

The scientists analysed the trend more closely and found further clues in soil moisture data for the country from the National Oceanic and Atmospheric Administration series of satellites. This data suggested a 300 per cent increase in pre-monsoon soil wetness over north-west India between 1988 and 2002. The study authors argue that the increase in soil moisture is due to irrigation during the pre-monsoon phase….

Despite the heavy clouds and sprinkle of rain (and despite it being Monday afternoon), famous Chowpatty beach is crowded with roamers, loiterers and visitors. Shot by McKay Savage, Wikimedia Commons via Flickr, under the Creative Commons Attribution 2.0 Generic license

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