Daily Mains Question - GS 1 - 24th September 2025
- TPP
- Sep 25
- 3 min read
Updated: Sep 25
Welcome to your Daily UPSC Mains Answer Writing Practice – GS Paper 1 (Geography & Environmental Issues).
Today’s question examines offshore aquifers, hidden freshwater reserves beneath the sea floor, and contrasts them with terrestrial aquifers in terms of their origin and structure. With studies estimating nearly 1 million km³ of undersea freshwater—around 10% of all terrestrial groundwater—these aquifers are emerging as potential game-changers in the context of global water scarcity.
For UPSC aspirants, the topic offers strong linkages across GS1 (physical geography, hydrological cycle, resource distribution), GS2 (water governance, international cooperation over maritime resources), and GS3 (disaster management, climate change adaptation, sustainable technologies). It provides scope to integrate UN reports, scientific studies, and case-based evidence while balancing opportunities with ecological and technological challenges.
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QUESTION
What are offshore aquifers, and how do they differ from terrestrial aquifers in terms of origin and structure? Discuss the potential importance of offshore aquifers in addressing global water scarcity.
Answer: Freshwater aquifers are vital subsurface reservoirs sustaining human societies for centuries. Beyond terrestrial systems, recent explorations have confirmed the presence of offshore aquifers—freshwater-bearing porous rocks or sediments beneath the sea floor. Studies suggest these undersea reserves could extend up to 90 km off the coast and hold more freshwater than all water ever extracted from land aquifers, offering new avenues to address the looming global freshwater crisis.
Offshore vs. Terrestrial Aquifers: Origin and Structure
Terrestrial Aquifers
Found beneath land, formed primarily by rainfall and snowmelt recharge.
Freshwater percolates through soil and porous rocks, stored under confined or unconfined conditions.
Recharge is continuous depending on precipitation, watershed conditions, and geological permeability.
Offshore Aquifers
Located beneath the seabed, often tens of kilometres offshore.
Freshwater may have accumulated during past ice ages, when sea levels were lower and present-day seabeds were exposed as land. Rainwater seeped into sediments, later preserved under the sea floor.
Alternatively, offshore aquifers may remain hydrologically connected to coastal aquifers, replenished by terrestrial recharge.
Protected by a cap rock of compacted clay-rich sediment, preventing upward mixing with saline seawater.
Example: The Atlantic offshore aquifer from New Jersey to Maine, estimated to provide water for a city like New York for ~800 years.
Global Evidence and Estimates
A 2021 study in Environmental Research Letters estimated ~1 million km³ of freshwater beneath the sea floor, about 10% of terrestrial groundwater reserves.
Confirmed sites include offshore regions of Australia, China, South Africa, and North America.
Drilling expeditions, e.g., off the US northeastern coast, reached depths of 1,289 feet and collected 50,000 litres of freshwater samples, confirming large-scale reserves.
Potential Importance in Addressing Water Scarcity
Global Water Crisis Context
According to the United Nations (2023), global freshwater demand is projected to exceed supply by 40% by 2030.
Climate change is intensifying droughts, erratic rainfall, and reduced snowmelt, lowering recharge of terrestrial aquifers.
Water pollution and inefficient usage further aggravate scarcity.
Strategic Significance of Offshore Aquifers
Untapped reserves: Provide alternative water sources for coastal megacities under stress.
Buffer against climate impacts: Can complement declining terrestrial recharge.
Geographical advantage: Many reserves are located near densely populated coastal belts, reducing transport distances.
Long-term security: If sustainably tapped, offshore aquifers could serve as strategic reserves in times of acute scarcity.
Challenges and Limitations
Economic Costs: Offshore drilling and exploration are capital-intensive; extraction off the US northeast cost nearly $25 million.
Technical Barriers: Designing wells beneath the seabed, preventing seawater intrusion, and transporting water onshore demand advanced engineering.
Environmental Concerns: Impact on marine ecosystems remains uncertain. Extraction could disturb seabed geology and habitats.
Finite Nature: If water trapped since the ice age is non-renewable, aquifers must be considered strategic reserves, not routine supplies.
Governance Issues: International maritime boundaries may complicate ownership and sustainable utilization.
Offshore aquifers represent a hidden frontier of freshwater resources, potentially alleviating the global water crisis amid rising demand and climatic stress. Their distinct origin and protective structure differentiate them from terrestrial systems. However, economic, technological, and ecological challenges imply that offshore aquifers should be approached as strategic emergency reserves, integrated with broader measures like water-use efficiency, demand management, and renewable desalination. Harnessing them prudently could contribute meaningfully to global water security in the 21st century.
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