Classification of surface-water - groundwater interaction of the Mokolo and Lephalala River systems in the Limpopo WMA

To be able to quantify the groundwater component of the Reserve, the groundwater volumes needed for basic human needs and ecological water requirements need to be quantified. The concept of the Groundwater Reserve and its focus on sustaining rivers and wetlands is not well developed. As a result, water-resource managers in the past decade have put the spotlight on hydrological issues such as groundwater - surface-water interaction. The aim of this investigation was to classify parts of the Mokolo River and lower Lephalala River. A simple classification scheme based on the geology and the hydraulic gradients between surface water and groundwater was used to characterise potential groundwater-surface water interactions. The study showed a clear interaction with the alluvial aquifer whereas a more complex interaction between the river bed and the host rock was identified. In this case a number of situations can occur, namely if the flux is high enough, groundwater will enter the river as baseflow, and if the flux is not high enough it could be used by riparian vegetation or enter the river at selected places. Classification of the river system can be regarded as one of the most important step in quantifying surface-water - groundwater interaction.