Advances in the Coastal and Submarine Groundwater Processes: Controls and Environmental Impact on the Thriassion Plain and Eleusis Gulf (Attica, Greece)

Demetrios Hermides,George Kontakiotis,Panayota Makri,Assimina Antonarakou

doi:10.3390/jmse8110944

Abstract

This study focuses on the hydrogeological conditions in the coastal (Thriassion plain) and submarine (Eleusis Gulf) environment of West Attica, Greece. Up to now, the predominant aspect for the Thriassion plain groundwater—hosted within the Neogene-Quaternary sediments—was its direct hydraulic contact with the seawater. Due to that, the coastal plain groundwater is strongly believed to be of brackish quality irrespective of the local hydrodynamic conditions. Our major goal is to evaluate the actual mechanism controlling the groundwater flow, the origin and distribution of saline water, and the existence of fresh groundwater in the submarine environment. We summarize the following: (1) groundwater of the Thriassion plain is partly discharged as an upwards leakage from deeper aquifers, (2) modern direct seawater intrusion is not possible in the Neogene-Quaternary sediments, and (3) fresh groundwater possibly exists below the sea floor of the Eleusis Gulf. The results may serve as hint of further research in groundwater resources below the Mediterranean Sea floor, and, consequently, a new perspective on water resource management could emerge.

Highlights

The sustainable management of coastal aquifer resources requires a good understanding of the relationship between salt and fresh water
The study on the Land Reclamation Service of Agricultural Ministry (LRSAM) data showed that the water level in most wells stood above the top of the aquifers as high as 1–5 m during the drillings phase
A completely revised hydrogeological conceptual model was proposed for the Thriassion Plain, West Attica, Greece

Summary

Introduction

The sustainable management of coastal aquifer resources requires a good understanding of the relationship between salt and fresh water. The common problem in coastal aquifers, which are hydraulically connected to the sea, is seawater intrusion mainly, but not exclusively, due to overpumping. Overpumping forces the salt-fresh water interface shift landward, resulting in the contamination of the fresh groundwater with seawater. This phenomenon is depended on (i) the geological-hydrogeological and hydraulic characteristics of the aquifer, (ii) human activities, and (iii) tidal effects and coastal and sea bottom conditions [5]. The hydrostatic equilibrium (Figure 1a) between salt and fresh water is described by the Ghyben-Herzberg principle, Equation (1): z=

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Conclusion