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

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 pr...

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Bibliographic Details
Published in:	Koedoe Vol. 62; no. 2; pp. 1 - 14
Main Authors:	Lorentz, Simon, Riddell, Edward S, Nel, Jaco, Van Tol, Johan, Fundisi, Daniel, Jumbi, Faith, van Niekerk, Ashton
Format:	Journal Article
Language:	English
Published:	Pretoria AOSIS 2020 African Online Scientific Information Systems (Pty) Ltd t/a AOSIS AOSIS (Pty) Ltd South African National Parks (SANParks)
Subjects:	Actual evapotranspiration Antecedent precipitation Aquifers Arid lands Arid zones Aridity Biodiversity Conservation Catchment area Catchments Climate Climate change Climate variability Connectivity Conservation Creeks & streams Drainage Drainage patterns Ecosystems Environmental aspects Environmental Sciences Ephemeral Evaporation Flow processes Global positioning systems GPS Granitic catchments Grasses Grasslands Groundwater Groundwater recharge Humidity Hydraulics Hydrochemistry Hydrology Landscape Moisture content National parks Observations Precipitation Preferential flow Protected areas Remote sensing Restoration Riparian land Rocks Savanna ecology Savannahs Savannas Soil Soil moisture Soil water Soil water storage Soils Streams Surface water Surface-groundwater relations Terrestrial ecosystems Vadose water Water balance Water, Underground Watersheds South Africa Granitic catchments Groundwater recharge Actual evapotranspiration Ephemeral Flow processes Savannas
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Summary:	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 secondand 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.
ISSN:	0075-6458 2071-0771 2071-0771
DOI:	10.4102/koedoe.v62i2.1583