ESTIMATING THE CONTRIBUTION OF PREFERENTIAL FLOW TO SUBSURFACE RUNOFFFROM A HILLSLOPE USING DEUTERIUM AND CHLORIDE

The concentrations of deuterium and chloride in rainfall, soil water a nd throughflow are reported for flow components through a mid-level ge ntly sloping hillside podzolic soil with a well developed network of m acropores. The deuterium and chloride signatures of the throughflow ar e shown to resemble that of rainfall rather than soil water for all ra infall events. Flow through macropores is considered to be the major m echanism for infiltration and throughflow. During the initial stages o f rainfall, infiltrating water bypasses much of the soil matrix and a transient water table is established. Storage associated with this wat er table dampens much of the noise from the deuterium and chloride sig nature of the rainfall while maintaining the mean rainfall signature. The possible implications on the use of stable isotopes and conservati ve tracers such as chloride for streamflow partitioning are discussed.