Changing rainfall patterns may be depleting India’s groundwater storage more than withdrawals for agricultural irrigation, says a new study published in January by Nature Geoscience.
While India’s diminishing groundwater is widely attributed to over extraction, especially in the northern agricultural belts of Punjab and Haryana, the study holds decline in rainfall caused by the rise in the temperatures in the Indian Ocean — a major factor in monsoonal rainfall patterns over the Indo-Gangetic Plain — to be a more important cause.
“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,” says Yoshihide Wada, co-author of the study and deputy director, Water Programme, International Institute for Applied Systems Analysis, Austria.
Importantly, the study finds links between the rise in sea surface temperatures of the Indian Ocean and the declining monsoonal rainfall which the study’s lead author Vimal Mishra says may be linked to climate change, though this is yet to be scientifically proven. Author Mishra, who is an assistant professor at the Indian Institute of Technology, Gandhinagar/Gujarat, adds that the rise in sea surface temperature in the Indian Ocean affects the rainfall in the Indo-Gangetic Plain. The long-term decline in rainfall in the area Plain is related to temperature in the Indian Ocean. This indirectly suggests that the declining trends may continue in the future because of this warming — which can affect water availability in the region.
India relies heavily on groundwater for irrigation particularly in the dry northern regions where precipitation is scarce. Groundwater withdrawal has increased tenfold — from 10-20 cubic kilometres per year in 1950 to 240-260 cubic kilometres in 2009. Satellite imagery shows major declines in groundwater, particularly in the north of the country.
India should avoid growing water-intensive crops in water-stressed regions such as Punjab, Mishra says in an interview with SciDev and suggests the development of policies and technology to improve groundwater recharge during the monsoon season and also improvement of irrigation efficiency through adoption of scientific methods such as the use of sprinkler and drip systems.