On fresh-saline groundwater in deltaic areas

http://freshsalt.deltares.nl/

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zoetzout.deltares.nl

Introduction

Salinisation causes problems for farmers, water managers and nature in many coastal areas of the world. Deltares has in-house databases, numerical modelling techniques, monitoring tools and the knowledge to thoroughly investigate salinisation issues and to implement innovative solutions for a robust climate proof fresh water supply in the coastal zone.

Threats to fresh water resources

Permanent groundwater drainage keeps the polder areas sustainable in a large part of The Netherlands accelerate due to the anticipated sea level rise, climate change, future land subsidence and especially due to human factors like groundwater extraction and lowering of differentiated polder water levels. The processes described here for the Dutch situation prevail in many other deltas and coastal areas. Concluding, not taking any mitigation and/or adaptation measures will lead to a world-wide increase of salinisation.

Focus on regional and local processes

Deltares researchers investigate the processes of fresh, brackish and saline groundwater on different scales. On a regional scale, the effects of climate change, land, and water use change and the combined effects of preventive measures on groundwater salinisation are studied. Other studies give answers on how groundwater concentration changes affect surface water quality. On a local scale, the dynamics of fresh rainwater lenses on saline groundwater as a result of natural or artificial recharge are studied. These lenses allow agriculture where shallow groundwater is very saline. Other research topics are preferential groundwater flow via sandy layers and boils that connect deep saline aquifers with shallow aquifers and with fresh surface water bodies. These preferential flow paths largely contribute to the salinisation of Dutch low-lying areas. Our knowledge is not specific for the Netherlands and can be applied in similar deltaic areas around the world.

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Solutions of salinisation problems

Deltares has the knowledge and expertise to study processes in combined fresh and saline groundwater systems. We develop and apply monitoring tools and techniques like the T-EC probe, EM-Slimflex and other online real-time measurement techniques. Moreover, Deltares has the modelling experience and the numeric compute codes (like MOCDENS3D/SEAWAT) at its disposal to simulate variable-density groundwater flow and coupled solute transport. Deltares is engaged in the design of specific measures needed for salinisation prevention and adaptation and for saline aquifer management. We have a long professional track record on groundwater salinisation studies built up during numerous relevant projects worldwide.