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Fig. 3. Experimental results of Henry and Smith (2002) after 202.5 h of surfactant solution (surfactant and dye tracer) application at a point source on the soil surface. Porous medium was a homogeneous fine sand with a capillary fringe thickness of approximately 55 to 60 cm. Ambient horizontal groundwater flow was from right to left in figure. The light gray area is the region that experienced surfactant-induced drainage. The darker region is a dye plume that was retarded relative to the movement of the drainage front. Dashed line above top of initial capillary fringe indicates that visual identification of the drainage front was difficult in those locations.
