Offshore aquifers

Why in news?

Recently, the international scientists have discovered the existence of large aquifer, under the Atlantic Ocean, first global expedition to drill systematically under the sea for freshwater.

• Offshore aquifers –
  • The offshore aquifer is just one of many depositories of freshwater known to exist in shallow salt waters around the globe.
  • Like aquifers on land, offshore aquifers are bodies of rock or sediment which contain freshwater.
  • Scientists believe that offshore aquifers can extend up to 90 kilometres off the coast and contain more freshwater than all the water that has ever been removed from aquifers on land.
• Extent - The scientists have confirmed the existence of offshore aquifers at several locations, including off the coasts of Australia, China, North America, and South Africa.
• It is estimated that there was a million cubic kilometers of freshwater beneath the sea floor about 10% of all terrestrial fresh groundwater.
• Source of freshwater – There are two theories -
  • Ice Age Hypothesis – The water might have reached beneath the sea floor, when sea levels were lower and large areas that are currently covered by the ocean were dry land.
  • As a result, rain trickled into the ground, building up large volumes of freshwater.
  • Connection Hypothesis - Offshore aquifers could be connected to onshore aquifers, which regularly supply them with water after rainfall.
• Freshwater Preservation - The freshwater beneath offshore aquifers may not be getting mixed with salty water due to a cap rock layer, built from compacted clay-rich sediment, over the aquifers.
• Challenges in extraction - offshore drilling is quite expensive; not clear about the impact of the ecology and marine life; and the issues of ownership and rights.
• Significance - Offshore aquifers can be untapped freshwater reserves and help deal with water scarcity on land.

According to a 2023 United Nations report, the world is currently facing an unprecedented water crisis, with global freshwater demand predicted to exceed supply by 40% by 2030.

A triple crisis - misusing water, polluting water, and changing the whole global hydrological cycle

Reference

Indian Express | Offshore aquifers