MONITORING THE BANK STORAGE DYNAMICS COMPONENT OF THE RIPARIAN WATER-BALANCE IN THE SABLE RIVER, KRUGER-NATIONAL-PARK

Transpiration by riparian vegetation is a major consumptive water use in natural river systems, and must be considered when making water all ocations for environmental conservation. Transpiration needs can be es timated by integrated modeling of bank storage dynamics, transpiration processes, and river hydraulics. Development and application of the b ank storage model require field data describing the response of the ph reatic surface to river stage fluctations, the spatial and temporal di stributions of water content in the unsaturated zone, and the geometry of the bedrock boundaries. A site on the Sable River in the Kruger Na tional Park, South Africa, is currently being monitored to collect suc h data. The phreatic surface response is interpreted to improve unders tanding of the nature of the subsurface flow, and its response to tran spiration. Measurement of soil moisture by neutron probe and laborator y analysis has confirmed the effectiveness and reliability of the neut ron probe method, and provided the necessary calibration data. Delinea tion of bedrock boundaries by physical probing and the use of ground-p enetrating radar has demonstrated the effectiveness of the radar techn ique.