A multidisciplinary approach to unravel the groundwater-surface water dynamics of the Kafue Flats, Zambia

The Kafue Flats wetland of Zambia is a vital surface water resource for both humans and animals alike. However anthropogenic disturbances to this wetland are effecting the wetlands perennial surface water bodies. One of the missing pieces in the puzzle in much of the research upon wetlands is groundwater-surface water interaction. The identification of groundwater inputs into a wetland allows stakeholders a greater understanding of the dynamics of the wetland. This aids in the effective management of this vital resource. This research has employed a multidisciplinary approach, incorporating remote sensing and hydrochemical and isotopic analysis. Remote sensing was employed using NDVI green island analysis to identify possible surface expressions of groundwater. The NDWI and MNDWI satellite indices were utilised within the Google Earth Engine, to identify perennial surface water bodies of the Kafue Flats. These green islands, perennial water bodies and groundwaters of the Kafue Flats were then hydrochemically and isotopically analysed, to investigate groundwater-surface water interactions. These methods identified that various groundwater flow systems (regional, intermediate and local) are feeding some surface water bodies of the Kafue Flats. The hydrochemical analysis identified a genetic link between surface waters and numerous rock types of the region, suggesting that there is a connectivity between the surface waters of the Kafue Flats and regional groundwater flow. It is hypothesised that this regional groundwater flow has connectivity with the surface waters of the Kafue Flats, due to the faulted nature of the contacts between the multiple aquifer lithologies. Surface expressions of groundwater sampled within this research, are found upon the delineated drainage networks that feed into the Kafue River. The hydrochemical signatures of these locations resemble a mixture between the hydrochemical signature of the rocks they are situated in, and the hydrochemical signature of the rocks that there specific drainage network/tributary has crossed. This has led to the identification that drainage network/tributary underflow may be an important mechanism of groundwater-surface water interactions within the Kafue Flats, responsible for supplying a flow of groundwater to surface water locations throughout the year