Spatial modelling of the hydrogeological connection between groundwater-dependent ecosystems and aquifers in the Kruger National Park, South Africa.
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Date
2025
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University of the Western Cape
Abstract
An improved understanding of the hydrogeological connection between aquifers and groundwater-dependent ecosystems (GDEs) is essential for an improved assessment and management of groundwater resources. In the Kruger National Park (KNP), which is also a prime conservation area of South Africa, groundwater plays the vital role of sustaining ecosystem functioning. Conducting hydrogeological assessments in this area will help to provide a robust methodological framework and a strategic tool for understanding groundwater flow and the influence of geology on groundwater occurrence and consequently the groundwater dependent ecosystems. This study therefore sought to assess the onnectivity
between groundwater-dependent ecosystems and groundwater in the Kruger National Park, South Africa. Two specific objectives were set mainly focussing on the characterisation of the aquifers within the KNP and secondly the delineation of GDEs in the KNP using freely accessible remote sensing data coupled with cloud computing approaches. To achieve the objectives of the study, the first step was to develop an understanding of the aquifers in the area. This was accomplished by utilizing pre-existing pumping test data to estimate the hydraulic parameters of the aquifers, as well as constructing geological cross- sections and analyzing borehole lithological core logs to identify preferential groundwater flow paths. Groundwater recharge was estimated using the cumulative rainfall departure and rainfall infiltration breakthrough methods. The analysis of the pumping test data showed that transmissivity ranged from 0.5 m2 d
-1 to 11.2 m2 d -1 , while storativity ranged from 1.28 × 10-6 to 4.38 × 10-4 . These results reveal that most of the selected boreholes have low transmissivity and storativity, as well as slightly high transmissivity for a few boreholes
drilled into the hard granite/gneiss rock. This suggested a porous but low permeability weathered aquifer, which agrees with the observed borehole lithological logs. Groundwater recharge received in the area ranged between 20.55 Mm3
a -1 and 29.4 Mm3 a -1. . The results further showed that groundwater mainly occurs/stored in joints, fractures, faults, zones of weathering and structures such as dyke intrusions. The site-specific conceptual model of the southern part of the KNP showed the aquifer mostly fractures to various extents. The area mostly consists of weathered rock material. GDEs were delineated using the weighted overlay tool. The thematic output layer was spatially classified into four classes: poor, fair, good and excellent according to the likelihood of GDE occurrence in the area. The results showed that only 2.39% of the total area is characterized by excellent likelihood of GDEs occurring. Most II of these areas are around rivers and areas on gentle slopes. The findings of this study demonstrate the effectiveness of incorporating hydrogeological study in understanding the relationship between GDEs and groundwater. The study therefore underscores the relevance of hydrogeological analysis for improved conceptualization of GDEs, rather than relying on surface indicators which do not consider connectivity between underlying aquifers and potential GDEs
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Keywords
Conceptual mode, hydrogeological connection, Kruger National Park, multi- criteria analysis, Numerical model