Abstract
Most river deltas are densely populated areas with intensive agriculture. The increased shortage of fresh surface water that results from rising demands are expected to lead to increased groundwater pumping, which leads to sea water intrusion. To correctly project the future of fresh groundwater resources in deltas, knowing the current fresh-salt groundwater distribution is a prerequisite. However, uncertainties about these distributions and their drivers are large. To understand these uncertainties, we conducted a global sensitivity analysis of a complex three-dimensional variable- density groundwater model of a synthetic delta, simulating the effect of the last glacial low stand and the subsequent marine transgression. The analysis is unique in its wide range of geometries, hydrogeological parameterizations, and boundary conditions analyzed, making it representative for a large number of deltas worldwide. We find that the aquifer hydraulic conductivity is the most uncertain input and has a strong nonmonotonous effect on the total salt mass onshore. The calculated fresh-salt groundwater distributions were classified into five classes and compared to real-world case studies. We find that salinity inversions occur in deltaic systems with high representative system anisotropies as a remnant of a marine transgression. These salinity inversions were observed in half of the real-world cases, indicating that their fresh-salt groundwater distributions are not in a dynamic equilibrium. We conclude that it is very likely that past marine transgressions are still reflected in the current fresh-salt groundwater distributions in deltas. This makes paleo-groundwater modeling a prerequisite for effective simulation of present-day groundwater salinity distributions in these systems.
| Original language | English |
|---|---|
| Article number | e2020WR027290 |
| Number of pages | 19 |
| Journal | Water Resources Research |
| Volume | 57 |
| Issue number | 1 |
| DOIs | |
| Publication status | Published - Jan 2021 |
Bibliographical note
Funding Information:We like to thank Perry de Louw for his helpful suggestions for our model setup. Furthermore, we like to thank two anonymous reviewers and Daniel Fernàndez‐Garcia for helping to improve this manuscript. This research has been supported by the Nederlandse Organisatie voor Wetenschappelijk Onderzoek (NWO) under the New Delta program (grant 869.15.013). This work was carried out on the Dutch national e‐infrastructure with the support of the SURF Cooperative, on a NWO Pilot Project Grant. The authors declare that they have no conssflict of interest.
Publisher Copyright:
© 2020. The Authors.
Keywords
- 3D
- global sensitivity analysis
- paleo-groundwater flow
- salt water intrusion
- variable-density groundwater model
