ABSTRACT
The severe degradation of the headwater wetlands of the Sand River, South Africa, by large erosion gullies has been the focus of a hydrological monitoring programme in order to determine the hydrodynamic response of these wetlands to rehabilitation interventions. This paper presents the findings relating to the behaviour of a headwater wetland’s groundwater phreatic surface prior to rehabilitation. The findings of hydrometric observations include the delineation of a stratified water table system. The behaviour of this suggests the occurrence of hydrodynamically distinct regions within the wetland, and loss of groundwater through head-cut erosion. Two Dimensional Electrical Resistivity Tomography (ERT) surveys identified a zone of finer sediment which is thought to act as a sub-surface flow buffer within this otherwise sandy wetland substrate. These findings suggest that these impacted wetlands need to be ‘plugged’ with a hydraulic stopper structure in order to restore their hydrological regime.
