Abstract
This paper analyzes the dynamic nature of the near stream flow mechanism in a forested mountain catchment, showing the flow mechanism changing with the antecedent conditions, magnitude and intensity of the rain. The transient nature of the near stream flow mechanism is demonstrated with stream bank tensiometer data. The stream SC (Specific Electric Conductance) behavior is explained by the different flow paths taken during different moisture content stages in the soil. The mobilization of near stream vadose zone water due to rain water input and possible later effect of blending of upslope water with near stream water are demonstrated. The direct correlation between pre-event base flow and after event baseflow SC values is shown and the relevant flow mechanism identified. Baseflow is shown to have a lower SC signal contrary to the normally expected high values. This result is verified in a laboratory soil column test. Physical and chemical data are presented to suggest the baseflow generation mechanism to be an unsaturated matrix flow along the clayey layer and the occasional upslope inputs to hydrographs to be saturated matrix flow along the semi impermeable boundary, once the water reaches that layer. The results of field investigations and soil column experiments show the feasibility of flow path determination by the chemical fingerprint on the stream and soil water samples.
