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Stability analysis of the unsaturated water flow equation: 2. Experimental verification
Author(s) -
Yao T.,
Hendrickx J. M. H.
Publication year - 2001
Publication title -
water resources research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.863
H-Index - 217
eISSN - 1944-7973
pISSN - 0043-1397
DOI - 10.1029/2001wr900003
Subject(s) - infiltration (hvac) , hydraulic conductivity , soil water , wetting , richards equation , water flow , materials science , soil science , mechanics , environmental science , geotechnical engineering , geology , composite material , physics
In this study, we verify the stability analysis of the unsaturated flow equation presented in paper 1. We compare finger sizes measured in laboratory experiments with predictions by the stability model. Using measured unsaturated hydraulic properties which are fitted and extrapolated over the entire water content range, the model enables us to predict finger sizes over a wide range of nonponding infiltration rates. The model predicts an increase of finger diameter at high and low infiltration rates for all soils. Such increases were also observed in our experiments. The model yields reliable predictions of finger diameters at high and intermediate infiltration rates but does not perform as well at infiltration rates <1 cm/h. This is caused by experimental limitations in accurately measuring hydraulic conductivities at low infiltration rates. A sensitivity analysis for initial water content and the shape parameter of the hydraulic conductivity curve showed that a small change of the parameters resulted in a relatively small change of finger size at high and intermediate infiltration rates but at low infiltration rates the finger size change was large, i.e., several orders of magnitude. We conclude that the stability model presented in paper 1 can be used for the assessment of wetting front instabilities in homogeneous soils over a wide range of nonponding infiltration rates.