Changing rainfall pattern linked to Indian Ocean warming

The changing rainfall pattern, which is linked to the warming of the Indian Ocean, is the key factor driving changes in groundwater storage in India, says a new study led by the Indian Institute of Technology (IIT) in Gandhinagar.

Published in the journal Nature Geoscience in January, the study shows that changing monsoon patterns "which are tied to higher temperatures in the Indian Ocean" are an "even greater driver of change" in groundwater storage than the pumping of groundwater for agriculture.

"Groundwater plays a vital role in food and water security in India. Sustainable use of groundwater resources for irrigation is the key for future food grain production," said study leader Vimal Mishra, of IIT Gandhinagar.

"And with a fast-growing population, managing groundwater sustainability is becoming even more important. The linkage between monsoon rainfall and groundwater can suggest ways to enhance groundwater recharge in India and especially in the regions where rainfall has been declining, such as the Indo-Gangetic Plain," he added.

Groundwater withdrawals in the country have increased over ten-fold since the 1950s, from 10-20 cubic kms per year in 1950 to 240-260 cubic kms per year in 2009. And satellite measurements have shown major decline in groundwater storage in some parts of the country, particularly in northern India, the study notes.

"This study adds another dimension to the existing water management framework. We need to consider not just the withdrawals, but also the deposits in the system," said Yoshihide Wada, co-author and the deputy director of the Water programme at the International Institute for Applied Systems Analysis in Austria.

By looking at water levels in wells around the country, the researchers could track groundwater replenishment following the monsoon.

In addition, the researchers found that the monsoon precipitation is correlated with Indian Ocean temperature, a finding which could potentially help to improve precipitation forecasts and aid in water resource planning.

"Weather is uncertain by nature, and the impacts of climate change are extremely difficult to predict at a regional level. But our research suggests that we must focus more attention on this side of the equation if we want to sustain manage water resources for the future", Wada added.

--IANS

sgh/sm/bg