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Powerful cyclones can affect groundwater quality in coastal areas: IIT-KGP study
Powerful cyclones can affect groundwater quality in coastal areas: IIT-KGP study
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Kolkata, Powerful cyclones can affect the quality of groundwater even 100 metres below the surface in deep coastal aquifers, posing a challenge to drinking water security, according to a recent study by IIT Kharagpur researchers.
The findings of the study, published recently in the journal 'Scientific Reports', examined the impact of extreme climatic events on groundwater systems in Sundarbans, part of the Ganga-Brahmaputra-Meghna delta and one of the world's most climate-vulnerable coastal regions.
The research, titled 'Groundwater vulnerability to Amphan and other recent cyclones in a tropical mega-delta', was conducted by IIT Kharagpur professors Abhijeet Mukherjee and Aditya Bandopadhyay, SRM University scientist Kousik Das and IIT Kharagpur research scholar Prakrity Majumder, the institute said in a statement on Tuesday.
Researchers studied 11 extreme climatic events between May 2017 and May 2020, including seven atmospheric depressions and four tropical cyclones Titli, Fani, Bulbul and Amphan, the study said.
Using groundwater-level measurements at multiple depths and conducting hydrogeochemical analysis, stable-isotope analysis and numerical modelling, the team examined changes in groundwater before, during and after the extreme weather events.
The study found that cyclones and atmospheric depressions can rapidly alter groundwater levels and hydraulic gradients at different depths, disturbing the balance between freshwater and seawater and facilitating the mixing of the two.
"Importantly, such changes were detected even in aquifers located more than 100 metres below the ground," the study said.
Shallow aquifers generally showed larger and more immediate fluctuations, while changes in deeper aquifers could persist for longer periods.
Analysis of stable isotopes provided additional evidence of water movement and mixing that may not be evident from groundwater-level measurements alone, the study said.
The findings are significant for densely populated coastal regions where groundwater is an important source of drinking water, it said.
The Ganga-Brahmaputra-Meghna delta is already facing multiple threats, including salinisation, arsenic contamination, human-induced pollution, groundwater stress and rising sea levels, it added.
The study indicates that extreme weather events can add another layer of vulnerability by temporarily changing groundwater flow and facilitating the movement of saline water within coastal aquifers.
The researchers' mass-balance assessment also found that the extent of seawater mixing differs between aquifers at different depths.
"This highlights the need for groundwater-management strategies that take into account the depth and characteristics of individual aquifers rather than treating coastal groundwater systems as a single, uniform unit," it said.
The researchers recommended continuous monitoring of groundwater at multiple depths and integrating extreme-weather forecasts into groundwater extraction and water-resource management plans.
Protecting deeper aquifers, regulating groundwater extraction and strategically locating wells away from areas vulnerable to seawater intrusion could become increasingly important for safeguarding freshwater resources in coastal regions, the study said.
The implications of the study extend beyond the Sundarbans, with tropical deltas and coastal regions across South and Southeast Asia and other parts of the world facing growing pressure from population growth, groundwater dependence, sea-level rise and extreme weather events, it said.
The findings show that the impact of cyclones on groundwater may extend well beyond the shallow subsurface, adding an important dimension to climate-resilience and water-security planning.
"Groundwater security must form an integral part of climate adaptation strategies, particularly in vulnerable coastal regions where millions of people depend on underground freshwater resources," it added.
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