Preprints
https://doi.org/10.5194/hess-2021-29
https://doi.org/10.5194/hess-2021-29

  11 Mar 2021

11 Mar 2021

Review status: this preprint is currently under review for the journal HESS.

Effects of aquifer geometry on seawater intrusion in annulus segment island aquifers

Zhaoyang Luo1,2, Jun Kong1,3, Chengji Shen1, Pei Xin1, Chunhui Lu1, Ling Li4, and David Andrew Barry2 Zhaoyang Luo et al.
  • 1State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering, Hohai University, Nanjing, China
  • 2Ecological Engineering Laboratory (ECOL), Environmental Engineering Institute (IIE), Faculty of Architecture, Civil and Environmental Engineering (ENAC), École Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
  • 3Jiangsu Key Laboratory of Coast Ocean Resources Development and Environment Security, Hohai University, Nanjing, China
  • 4School of Engineering, Westlake University, Hangzhou, China

Abstract. Seawater intrusion in island aquifers is considered analytically, specifically for annulus segment aquifers (ASAs), i.e., aquifers that (in plan) have the shape of an annulus segment. Based on the Ghijben-Herzberg and hillslope-storage Boussinesq equations, analytical solutions are derived for steady-state seawater intrusion for ASAs, with a focus on the freshwater-seawater interface and its corresponding watertable elevation. These analytical solutions, after comparing their predictions with experimental data, are employed to investigate the effects of aquifer geometry on seawater intrusion in island aquifers. Three different geometries of ASA are compared: convergent (smaller side facing the lagoon), rectangular and divergent (larger side facing the sea). The results show that the predictions from the analytical solutions are in well agreement with the experimental data for both recharge events. In addition, seawater intrusion is most extensive in divergent aquifers, and conversely for convergent aquifers. Accordingly, the watertable elevation is lowest in divergent aquifers and highest in convergent aquifers. Moreover, the effects of aquifer geometry on the freshwater-seawater interface and watertable elevation vary with aquifer width and distance to the no-flow boundary. Both a larger aquifer width and distance to the no-flow boundary weaken the effects of aquifer geometry and hence lead to a smaller deviation of seawater intrusion between the three geometries.

Zhaoyang Luo et al.

Status: open (until 10 May 2021)

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Zhaoyang Luo et al.

Zhaoyang Luo et al.

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Short summary
We develop analytical solutions to examine the effects of aquifer geometry on seawater intrusion. These analytical solutions are validated by comparing their predictions with experimental data. We find seawater intrusion is most extensive in divergent aquifers, and conversely for convergent aquifers. The analytical solutions facilitate engineers and hydrologists to evaluate seawater intrusion more efficiently in aquifers with different geometries.