Offshore Freshened Groundwater (OFG) is a potentially strategic resource for coastal water security. Despite its discovery in the 1960s and estimates of substantial global volumes, OFG remains poorly understood. Existing data are sparse and largely incidental, originating from offshore hydrocarbon drilling. Research efforts so far have lacked coordinated approaches to assess OFG’s potential for sustainable use.

Advancing the understanding of OFG systems requires research into their emplacement history and age, as well as recharge and discharge mechanisms. Investigations into permeability, porosity, and fluid flow pathways will improve predictions of OFG behaviour under natural conditions and potential utilisation scenarios. Fluid flow processes, hydraulic properties, and connectivity between onshore and offshore aquifers must be studied to assess long-term viability and estimate the sustainable yield of an OFG reservoir. Understanding recharge processes under current conditions should be a prerequisite before any large-scale exploitation, as abstraction could significantly impact the freshwater-saltwater interface.

Scope of the call

The primary objective of this Joint Call is to act as a “proof of concept” through the launch of a pioneering scientific drilling campaign that integrates hydrogeological and geochemical characterisation, with pumping tests, to validate OFG systems and generate critical data on their distribution, properties, recharge mechanisms, and long-term viability as a resource. 

This initiative aims to lay the groundwork for the potential future strategic use and sustainable management of OFG resources. The campaign will target knowledge gaps, including: 

• Data scarcity and inconsistency: generating systematic and comprehensive data on OFG properties and dynamics.

• Environmental, technological, and economic feasibility: assessing the environmental impacts and evaluating the technological and economic viability of potential OFG utilisation.

• Legal and governance frameworks: informing and potentially contributing to the development of guidelines and regulatory frameworks for the integration of OFG exploration and exploitation into existing regimes. 

The following themes are identified as priorities for the Joint Call:

1. Characterisation, validation, and assessment of offshore freshened groundwater bodies, through a drilling campaign. Scientific questions originated from knowledge gaps: 

• Functioning of OFG systems and onshore-offshore connectivity

• Age of emplacement of the OFG

• Hydraulic and hydrogeologic properties

• Potential environmental impacts emerging from use of OFG 

2. Environmental assessment of offshore freshened groundwater seeps (developing environmental baselines)

• Seep characterisation (functioning of seepage)

• Seep-related ecosystems characterisation (bio-geochemical aspects)

• Monitoring 

The geographical spread of the proposed research should include the northern Adriatic Sea but will not exclude studies in other European marine basins, including other marginal seas of the Mediterranean Sea, the North Sea and the Baltic Sea.

This call is expected to be launched on 4 December 2025 with a deadline on 6 March 2026.

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