Narasimhan, 1985; Evans and Nicholson, 1987; Peters and. Klavetter, 1988 ... The rock ledge can be either a natural small cliff or an exca- vated rock ledge.
WATER RESOURCES RESEARCH, VOL. 35, NO. 11, PAGES 3315-3326,NOVEMBER 1999
Field observationof flow in a fracture intersecting unsaturated
chalk
Ofer Dahan, • Ronit Nativ, • Eilon M. Adar, 2 Brian Berkowitz,3 and Zeev Ronen2
Abstract. Flow througha naturalfracturecrossing unsaturated chalkin an arid region wasinvestigated in a field experimentusinga speciallydesignedexperimentalsetup.The setupallowedcompletecontrolof the flow domaininlet and outlet. Water flux into and out of the fracturewasmeasuredin smallsegments of the fractureopenings,and flow trajectories were identifiedusingsevenfluorobenzoic acidtracers.A 5 daypercolation experimenton a 5.3 rn longfractureshowedsignificantspatialand temporalvariabilityof the flow regime.Flow throughfractureopeningsdid not reacha steadystateeither in individualsegments or acrossthe entire flow domain,althoughthe boundaryconditions were kept relativelysteadyfor the entire durationof the experiment.Flow trajectories within the fractureplanevaried over time; however,mostof the flow wasconfinedto smallsectionsof the fracture.Over 70% of the fluxwastransmittedthrough
