A hydrogeological study of the Kasteelberg Mountain aquifer, Western Cape, South Africa

Pieters, Bernardus Lambertus (2020-03)

Thesis (MSc)--Stellenbosch University, 2020.

Thesis

ENGLISH ABSTRACT: The availability of freshwater is one of the major factors that are limiting South Africa’s development. With this in mind the area under investigation in this study forms part of the Sandspruit catchment, which is about 100 km north-east of Cape Town near the town of Riebeek Kasteel. The climate is semi-arid with a Mediterranean landscape. This study forms part of multiple studies that were initiated to assist in alleviating the crisis brought about by the continuing drought in the Western Cape Province. This study investigated the possibility of utilising the Kasteelberg Mountain, located near the town of Riebeek Kasteel, as an additional source of freshwater. The regionally fractured sandstone aquifer was the focus during the modelling, volume and porosity calculations in this hydrogeological research of the Kasteelberg Mountain Aquifer. This resulted in an estimated water reserve that can be sustainably extracted. Sustainable development is needed to protect the sensitive ecosystems against anthropologic and climate-driven impacts. The study started with analysing the responses from water level loggers that were installed in boreholes in the study area to monitor the water fluctuations during the seasons so as to utilise this resource sustainably. During the study, the physical geology of the area was characterised. Geographic Information Systems (GISs) were used to generate maps and derive volumetric information needed to estimate water volumes, and this included the delineation of the watershed, elevation and the spatial maps of the boreholes that were monitored. A cascade model was created by using climate data collected from local weather stations and the physical character of the local sandstone to study the waterflow through the mountain. The cascade model was used to appraise its potential in runoff. Some common features between the proposed model and HYDRUS-1D runoff model are also discussed. Data was also used in the HYDRUS-1D model where the results generated were compared with the cascade model results and the measured results from fieldwork studies. The study therefore reflected on the volume of water present in the mountain aquifer and despite the area experiencing its worst drought in a century, this excess water was available for extraction.

AFRIKAANSE OPSOMMING: Die studie-area vorm deel van die Sandspruit-opvangsgebied. Die klimaat is semi-droog en kan beskryf word as ’n bedreiging vir ontwikkeling. ’n Studie is gedoen met die hoop om ʼn addisionele varswaterbron te vind. Hierdie studie vorm deel van ʼn groter studie wat ten doel het om die droogtegeteisterde Wes-Kaap se druk te verlig deur addisionele varswaterbronne te vind. Die studie fokus op die Kasteelberg, wat net buite die dorp Riebeek Kasteel geleë is. Tydens hierdie hidrologiese ondersoek is daar gevind dat die akwifer hoofsaaklik bestaan uit sandsteen wat deel van die Tafelberg Groep vorm. Nate en krake is ook volop in hierdie poreuse sandsteenrotse. Vir die doeleindes van hierdie studie is die akwifer as homogeen met betrekking tot sy geologiese samestelling beskou. Die studie het grondwatervlakregistreerders geïnstalleer in bestaande boorgate om die seisoenale waterfluktuering te meet. Die fisiese karakterisering van die geologie is onderneem waar die totale porositeit en samestelling eerstens vasgestel is. Geografiese Inligtingstelsels (GIS)- sagteware is gebruik om die berg te karteer, asook die waterskeidings af te lei, oppervlaktes te bepaal, metings van die berg te doen en die verspreiding van die toetsboorgate te karteer. Plaaslike weerstasiedata is bekom en deur middel van die opstel van ’n kaskade-model in MS Excel is die geofisiese inligting ingespan om meer te ontdek van die water wat deur die berg vloei. Excel is dus ook gebruik om die volume van die akwifer te bepaal en die model kon die waterdravermoë van die akwifer benader. Excel-resultate is gevolglik vergelyk met die HYDRUS-1D-model se resultate en die model het die Excel-resultate bevestig en met fisiese waarnemings ooreengestem wat in die veld gemaak was. Die studie het daarin geslaag om te bewys dat hoewel die Wes-Kaap tans deur die ergste droogte in 100 jaar geteister word, die Kasteelberg Akwifer steeds genoeg neerslag ontvang om as waterbron vir plaaslike ontginning te dien, wat sodoende die druk op die bestaande waterinfrastruktuur sal kan verlig.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/107835
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