Original Research - Special Collection: Granite catena ecosystem

Groundwater–surface water interactions in an ephemeral savanna catchment, Kruger National Park

Edward S. Riddell, Jaco Nel, Johan van Tol, Daniel Fundisi, Faith Jumbi, Ashton van Niekerk, Simon Lorentz
Koedoe | Vol 62, No 2 | a1583 | DOI: https://doi.org/10.4102/koedoe.v62i2.1583 | © 2020 Edward S. Riddell, Jaco Nel, Johan van Tol, Daniel Fundisi, Faith Jumbi, Ashton van Niekerk, Simon Lorentz | This work is licensed under CC Attribution 4.0
Submitted: 05 September 2019 | Published: 29 October 2020

About the author(s)

Edward S. Riddell, South African National Parks, Conservation Management, Skukuza; Centre for Water Resources Research, University of KwaZulu-Natal, Pietermaritzburg, South Africa
Jaco Nel, Institute for Water Studies, University of the Western Cape, Cape Town; Groundwater Consulting Services, Pretoria, South Africa
Johan van Tol, Department of Soil, Crop and Climate Sciences, Faculty of Science and Agriculture, University of the Free State, Bloemfontein, South Africa
Daniel Fundisi, Centre for Water Resources Research, University of KwaZulu-Natal, Pietermaritzburg; Digby Wells Environmental (Pty) Ltd, Johannesburg, South Africa
Faith Jumbi, Centre for Water Resources Research, University of KwaZulu-Natal, Pietermaritzburg; Department of Earth Science, Faculty of Natural Science, University of the Western Cape, Cape Town, South Africa
Ashton van Niekerk, Institute for Water Studies, University of the Western Cape, Cape Town; Department of Human Settlements, Water and Sanitation, University of Western Cape, Cape Town, South Africa
Simon Lorentz, Centre for Water Resources Research, University of KwaZulu-Natal, Pietermaritzburg; SRK Consulting, Pietermaritzburg, South Africa


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Abstract

The semi-arid conditions in savanna landscapes ensure that ephemeral drainage dominates the hydrological network in these dryland systems. Quantification of their hydrological processes is important to inform ecosystem understanding and future conservation efforts under a changing climate, and to provide guidance for restoration. By combining in situ hydrometric observations, hydrochemistry, remote sensing and a soil water balance model, we characterise the groundwater–surface water interactions in ephemeral low-order catchments of the granitoid regions of the southern Kruger National Park (KNP). Streams at the lowest orders are augmented by lateral interflows from the catena, although the second- and third-order stream reaches are conduits for groundwater recharge to the fractured rock aquifer; the soils of the crests and foot-slopes also show preferential flow, and are truly recharge soils, whilst the duplex soils of the midslopes clearly show their responsive nature to a low soil moisture deficit in the shallow horizons. Actual evaporation (aET) differed between catena elements with surprisingly little variation at third-order hillslopes, with the greatest overall aET at the first order. Meanwhile, soil water balances demonstrated a significant variation in storage of the riparian zones as a result of interflow from upslope and aET losses. Furthermore, data support broader-scale observations that groundwater recharge through the vadose zone to the fractured rock aquifer is dependent upon threshold antecedent precipitation conditions. Moderate precipitation events (5 mm/day – 35 mm/day) over a 2–3 week period initiate groundwater responses with a 2–3 month lag, whilst intense precipitation events (>100 mm/day) are expressed within 2–3 weeks.

Conservation implications: Understanding the lateral connectivity of terrestrial ecosystems to the ephemeral drainage network expressed via hydrological processes in these savanna landscapes is important to infer potential impacts of climate variability on the continued conservation of these ecosystems, both within and external to protected areas.


Keywords

Flow processes; Groundwater recharge; Actual evapotranspiration; Ephemeral; Granitic catchments; Savannas

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Crossref Citations

1. Connections between abiotic and biotic components of a granite catena ecosystem in Kruger National Park
Beanelri B. Janecke, Johan van Tol
KOEDOE - African Protected Area Conservation and Science  vol: 62  issue: 2  year: 2020  
doi: 10.4102/koedoe.v62i2.1638