According to a study conducted by researchers at the Indian Institute of Technology Gandhinagar (IIT GN), North India accounts for 95 per cent of the country's groundwater depletion. The study also found an increase in rainfall in the future will be insufficient to fully recover the already depleted resources.
The researchers found that until excessive pumping is limited, groundwater depletion in India will continue, leading to water sustainability issues in the future, stated a report by PTI. They also added that non-renewable (unsustainable) pumping has a dominant influence on groundwater storage, causing the water table to drop.
What the researchers say
"Limiting tube well depth and including extraction costs is beneficial to prevent overexploitation of deep aquifers," said Vimal Mishra, Professor, Civil Engineering and Earth Sciences, IIT Gandhinagar. "Limiting global mean temperature rise within 2 degrees Celsius can benefit groundwater storage in North India," Mishra added, as stated by the PTI report.
The researchers analysed data from the Central Groundwater Board (CGWB) in-situ groundwater well levels and satellite observations to study groundwater storage variability and the study was recently published in the journal, One Earth.
The team then used global climate model projections having different future warming scenarios for hydrological model simulations. Swarup Dangar, a PhD scholar in Civil Engineering at IIT Gandhinagar was part of the team. They estimated the relative contribution of groundwater pumping and recharge on future changes in groundwater storage. The wettest historical and future periods support partial groundwater recovery despite the continuing abstraction from non-renewable groundwater resources, they added.
The study shows that the projected increase in precipitation may not directly translate to an increase in groundwater storage. The positive impact of the increase in rainfall will be affected by the rise in the potential evapotranspiration (PET) due to the warming climate.
Getting into more details
"It is crucial to reduce groundwater depletion to maintain sustainable groundwater resources in the region, even if there is an expected increase in precipitation that could help recharge the groundwater," Dangar told PTI. He further added, "Even with an increase in precipitation, excessive groundwater withdrawal can lead to the drying or deepening of wells. Additionally, information on the costs associated with deeper groundwater pumping could inform better groundwater use and management practices."
The researchers noted the excessive pumping of groundwater due to the decline in precipitation and the rapid increase in tube wells for groundwater abstraction as a factor leading to a severe depletion of groundwater resources in North India. They also found that during the pre and post-monsoon seasons in North and Central India, the groundwater is mainly used for irrigation of rice and wheat crops.
Meanwhile, the study attributed the recent increase in groundwater storage in South India to a rise in rainfall during the monsoon season. The researchers further clarified that the limit of groundwater depletion is not yet clear, however, the depletion of deeper groundwater resources can make pumping water economically unviable.
"It may be useful to shift crop growing and procurement areas or switch to less water-intensive cereals and improve water use efficiency in irrigation," Mishra added.
