SEPARATION OF SUBSURFACE AND GROUNDWATER COMPONENTS IN A RIVER WITH SANDBAR

Abstract

The characteristics of surface-subsurface water interaction in a river with sandbar are threedimensional. The exchange phenomena at the surface-subsurface water interface are still unknown. An investigation has been carried out by tracer experiment and vertical 2D (V2D) simulation at the interface with various bed shapes and hydraulic conditions to understand the phenomena as well as to delineate the subsurface water and groundwater components. The flow properties at the surface and subsurface zone are verified by 1D Darcy theory. A line, which separates the subsurface and ground water components, is determined for individual cases. The experiment as well as V2D simulation shows that at the interface subsurface water components are found to be about 80-90% of the total flow (subsurface plus groundwater) components. The subsurface flow is found to be two-dimensional within the surface water zone and one-dimensional at the subsurface zone, which satisfies the Dupuit's assumption.