Infiltration into fractured bedrock

• Published in: Water resources research 2008-01, Vol.44 (1), p.n/a
• Main Authors: Salve, Rohit, Ghezzehei, Teamrat A., Jones, Robert
• Format: Article
• Language: English
• Subjects: fractures; Infiltration; rock
• ISSN: 0043-1397; 1944-7973
• DOI: 10.1029/2006WR005701

One potential consequence of global climate change and rapid changes in land use is an increased risk of flooding. Proper understanding of floodwater infiltration thus becomes a crucial component of our preparedness to meet the environmental challenges of projected climate change. In this paper, we present the results of a long‐term infiltration experiment performed on fractured ash flow tuff. Water was released from a 3 × 4 m2 infiltration plot (divided into 12 square subplots) with a head of ∼0.04 m, over a period of ∼800 days. This experiment revealed peculiar infiltration patterns not amenable to current infiltration models, which were originally developed for infiltration into soils over a short duration. In particular, we observed that in part of the infiltration plot, the infiltration rate abruptly increased a few weeks into the infiltration tests. We suggest that these anomalies result from increases in fracture permeability during infiltration, which may be caused by swelling of clay fillings and/or erosion of infill debris. Interaction of the infiltration water with subsurface natural cavities (lithophysal cavities) could also contribute to such anomalies. This paper provides a conceptual model that partly describes the observed infiltration patterns in fractured rock and highlights some of the pitfalls associated with direct extension of soil infiltration models to fractured rock over a long period.