Abstract
Excessive freshwater pumping in coastal areas result in an inland intrusion of the saltwater wedge underlying the freshwater aquifer, leading to salinization of coastal aquifers. While multiple approaches and techniques in the form of analytical solutions, numerical simulations, mass balance calculations and laboratory experiments have been used to study the flow dynamics of the density-driven circulation of saltwater, little is known regarding the groundwater ages in coastal aquifers and the process timescales. The current study makes use of multiple age tracers such as 3H, 85Kr and 39Ar, allowing to calculate both modern and sub-modern groundwater ages. The ages derived based on the measured tracer values were compared to a numerical flow simulations. The results indicate that seawater intrusion in the Nitzanim coastal reserve (prompted by excessive freshwater pumping upstream) has a different effect on the ages of the shallow groundwaters in comparison with the deeper groundwater. Close to the shoreline (<~200 m) at shallow depths (<40 m below sea level), the intruding saline groundwater is younger than the freshwater system leading to young ages of <50 years. Further away from the shoreline (~700 m), at greater depths (~60 m below sea level), the deep intruding saline groundwater is dated to ~350 years, which is significantly older than fresh groundwater ages in this part of the coastal aquifer. The approach brought forward in the paper allows to better understand the timescales of density-driven circulation mechanism and the effect of seawater intrusion on groundwater ages.
| Original language | English |
|---|---|
| Article number | 125721 |
| Journal | Journal of Hydrology |
| Volume | 597 |
| DOIs | |
| State | Published - Jun 2021 |
Bibliographical note
Funding Information:We dedicate this work to the late Chaim Chemo, our colleague and friend who led countless field expeditions during his career at the Geological Survey of Israel, including the field work conducted for this study. We thank the Israel Water Authority, for collecting and providing the water table elevation data and Nimrod Rabinovitch for generating the water table elevation maps. We thank Shaked Stein for the EC profile measurements in the Nitzanim coastal reserve. We thank the staff of the geochemical laboratories at the Geological Survey of Israel for their precise analytical work and results. Dr. Avihu Burg is thanked for providing initial feedback regarding the premise of the work. Finally, the authors appreciate and thank the two anonymous reviewers, the Associate Editor, Dr. Vincent E.A. Post and the Editor-in-Chief, Prof. Corrado Corradini, for their detailed review which gave us the opportunity to improve the quality of this manuscript.
Publisher Copyright:
© 2020
Keywords
- 39Ar
- 3H-3He
- 85Kr
- Coastal aquifer
- Groundwater dating
- Seawater intrusion
