Monsoon rainfall changes affecting groundwater level
doi:10.1038/nindia.2017.18 Published online 7 February 2017
Excessive pumping for agriculture may not be the prime reason behind plummeting groundwater tables in India, a new study says, suggesting instead that long-term changes in monsoon rainfall could be the key reason influencing groundwater storage1.
Analysing precipitation and water extraction data from satellites records and ground wells, researchers from India and the USA found that declining monsoon rainfall has been adversely affecting groundwater storage in India.
The effect of a weakening monsoon was most pronounced in north-central India, where variability in groundwater storage was mostly due to decrease in precipitation. In north-western India, both abstraction and precipitation were found to influence groundwater storage. However, higher abstraction rates were also the result of a monsoon system losing steam.
Between 2002 and 2013, groundwater storage in northern India decreased by 2 cm a year on an average. Interestingly, in southern India, storage increased at the rate of 1 to 2 cm per year, even though the number of ground wells in the southern states has seen a rapid increase.
The researchers also found a link between a warmer Indian Ocean and a decrease in rainfall over north India, eventually leading to higher groundwater abstraction in the region. This teleconnection, unrecognized so far, between sea surface temperature and groundwater storage needs further study.
Vimal Mishra, one of the lead researchers from Indian Institute of Technology Gandhinagar, says there’s need to ramp up recharge activities in rainy season and ensure efficient usage of groundwater in dry season.