The groundwater level in north India has been declining at a rate of 2 cm per year during the period 2002-2013, while in north-central and south India, it has increased by 1-2 cm per year during the same period, says a study carried out by a team of researchers from the Indian Institute of Technology (IIT) Gandhinagar.
While changes in monsoon rainfall pattern during the period of study can largely explain the total variability of groundwater storage in north-central and south India, the usage of groundwater for irrigation purposes accounts for groundwater variability in northwest India. The increased usage of groundwater for irrigation in northwest India is, in turn, linked to changes in monsoon rainfall pattern. The results were published in the journal Nature Geoscience.
“A 2009 study carried out in Punjab and Haryana showed that groundwater extraction was mainly responsible for declining groundwater storage. But our study shows that changes in groundwater storage are linked to changes in rainfall pattern in most parts of India,” says Prof. Vimal Mishra from the Civil Engineering Department, IIT Gandhinagar and the corresponding author of the paper. “In north-central and south India, rainfall is a major driver of groundwater storage change. But in northwest India, groundwater pumping is a major cause of groundwater storage variability,” he said.
Reduced monsoon rainfall in north India due to Indian Ocean warming has led to reduced groundwater storage and increased usage of groundwater for irrigation.
For instance, over the Gangetic Plain and other parts of north India monsoon rainfall has been declining since 1950, leading to reduced recharge of groundwater.
As a result of declining monsoon rainfall and intensive agriculture, groundwater withdrawals in the country have increased over tenfold since the 1950s — from 10-20 cubic km per year in 1950, to 240-260 cubic km per year in 2009.
Prof. Mishra’s team used GRACE satellite data to estimate groundwater storage anomalies.
They also used information on groundwater levels from observation wells.