Field observation of flow in a fracture intersecting unsaturated chalk

Ofer Dahan, Ronit Nativ, Eilon M. Adar, Brian Berkowitz, Zeev Ronen

Research output: Contribution to journalArticlepeer-review

86 Scopus citations

Abstract

Flow through a natural fracture crossing unsaturated chalk in an arid region was investigated in a field experiment using a specially designed experimental setup. The setup allowed complete control of the flow domain inlet and outlet. Water flux into and out of the fracture was measured in small segment of the fracture openings, and flow trajectories were identified using seven fluorobenzoic acid tracers. A 5 day percolation experiment on a 5.3 m long fracture showed significant spatial and temporal variability of the flow regime. Flow through fracture openings did not reach a steady state either in individual segments or across the entire flow domain, although the boundary conditions were kept relatively steady for the entire duration of the experiment. Flow trajectories within the fracture plane varied over time; however, most of the flow was confined to small sections of the fracture. Over 70% of the flux was transmitted through <20% of the studied fracture openings. Observations from the tracer tests suggest that flow paths can coexist near each other without water mixing, probably because the fracture fill generates unconnected flow paths across the main fracture void.

Original languageEnglish
Pages (from-to)3315-3326
Number of pages12
JournalWater Resources Research
Volume35
Issue number11
DOIs
StatePublished - 1 Jan 1999

ASJC Scopus subject areas

  • Water Science and Technology

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