The usefulness of outcrop analogue air permeameter measurements for analyzing aquifer heterogeneity: Quantifying outcrop hydraulic conductivity and its spatial variability

Bart Rogiers, Koen Beerten, Tuur Smeekens, Dirk Mallants, Matej Gedeon, Marijke Huysmans, Okke Batelaan, Alain Dassargues

Research output: Contribution to journalArticlepeer-review

5 Citations (Scopus)

Abstract

Saturated hydraulic conductivity (K) is one of the most important parameters determining groundwater flow and contaminant transport in both unsaturated and saturated porous media. Although several well-established laboratory methods exist for determining K, in situ measurements of this parameter remain very complex and scale dependent. Often, the limited accessibility of subsurface sediments for sampling means an additional impediment to our ability to quantify subsurface K heterogeneity. One potential solution is the use of outcrops as analogues for subsurface sediments. This paper investigates the use of air permeameter measurements on outcrops of unconsolidated sediments to quantify K and its spatial heterogeneity on a broad range of sediment types. The Neogene aquifer in northern Belgium is used as a case study for this purpose. To characterize the variability in K, 511 small-scale air permeability measurements were performed on outcrop sediments representative over five of the aquifer's lithostratigraphic units. From these measurements, outcrop-scale equivalent K tensors were calculated using numerical upscaling techniques. Validation of the air permeameter-based K values by comparison with laboratory constant head K measurements reveals a correlation of 0.93. Overall, the results indicate that hand-held air permeameters are very efficient and accurate tools to characterize saturated K, as well as its small-scale variability and anisotropy on a broad range of unconsolidated sediments. The studied outcrops further provided a qualitative understanding of aquifer hydrostratigraphy and quantitative estimates about K variability at the centimetre-scale to metre-scale.

Original languageEnglish
Pages (from-to)5176-5188
Number of pages13
JournalHydrological Processes
Volume28
Issue number20
DOIs
Publication statusPublished - Sep 2014

Keywords

  • Air permeameter
  • Anisotropy
  • Hydraulic conductivity
  • Sedimentary structures
  • Spatial variability
  • Upscaling

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