Coupling ground and airborne geophysical data with upscaling techniques for regional groundwater modelling of heterogeneous aquifers: case study of a sedimentary aquifer intruded by volcanic dykes in Northern Ireland

Neil Edwin Matthew Dickson, Jean-Christophe Comte, Jennifer McKinley, Ulrich Ofterdinger

Research output: Contribution to journalArticlepeer-review

15 Citations (Scopus)

Abstract

In highly heterogeneous aquifer systems, conceptualization of regional groundwater flow models frequently results in the generalization or negligence of aquifer heterogeneities, both of which may result in erroneous model outputs. The calculation of equivalence related to hydrogeological parameters and applied to upscaling provides a means of accounting for measurement scale information but at regional scale. In this study, the Permo-Triassic Lagan Valley strategic aquifer in Northern Ireland is observed to be heterogeneous, if not discontinuous, due to subvertical trending low-permeability Tertiary dolerite dykes. Interpretation of ground and aerial magnetic surveys produces a deterministic solution to dyke locations. By measuring relative permeabilities of both the dykes and the sedimentary host rock, equivalent directional permeabilities, that determine anisotropy calculated as a function of dyke density, are obtained. This provides parameters for larger scale equivalent blocks, which can be directly imported to numerical groundwater flow models. Different conceptual models with different degrees of upscaling are numerically tested and results compared to regional flow observations. Simulation results show that the upscaled permeabilities from geophysical data allow one to properly account for the observed spatial variations of groundwater flow, without requiring artificial distribution of aquifer properties. It is also found that an intermediate degree of upscaling, between accounting for mapped field-scale dykes and accounting for one regional anisotropy value (maximum upscaling) provides results the closest to the observations at the regional scale.
Original languageEnglish
Pages (from-to)7894-8001
Number of pages18
JournalWater Resources Research
Volume50
Issue number10
Early online date16 Oct 2014
DOIs
Publication statusPublished - Oct 2014

Bibliographical note

Funded by
Northern Irish Department of Education and Learning

Acknowledgments

This work was carried out thanks to a PhD scholarship funding from the Northern Irish Department of Education and Learning. We acknowledge the Northern Ireland Environment Agency for supplying regional pumping rates and the Geological Survey of Northern Ireland for supplying Tellus airborne geophysical data, borehole records, and GIS shapefiles; in particular, Alex Donald, Mark Cooper, and William Smyth. Hugh Anderson from Midland Valley is also thanked for supplying GIS dyke shapefiles as well as Philippe Renard and Jean-Michel Vouillamoz for their comments regarding the work during personal discussions. Finally, we are grateful to the associate editor and anonymous reviewers for their constructive comments and suggestions which have contributed to improving the quality of the manuscript.

Keywords

  • groundwater
  • dykes
  • modeling
  • geophysics
  • upscaling
  • anisotropy

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