Evaluating groundwater storage changes under drought in the Western Cape using satellite and in-situ data

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dc.contributor.advisorChow, Reynolden_ZA
dc.contributor.advisorWatson, Andrewen_ZA
dc.contributor.authorNenweli, Ritshidzeen_ZA
dc.contributor.otherStellenbosch University. Faculty of Science. Dept. of Earth Sciences.en_ZA
dc.date.accessioned2023-02-27T09:45:31Z
dc.date.accessioned2023-05-18T07:02:45Z
dc.date.available2023-02-27T09:45:31Z
dc.date.available2023-05-18T07:02:45Z
dc.date.issued2023-03
dc.descriptionThesis (MSc)--Stellenbosch University, 2023. en_ZA
dc.description.abstractENGLISH ABSTRACT: The Western Cape is a water scarce province of South Africa and has become more reliant on groundwater over the last few decades due to frequent droughts, which are anticipated to worsen in the future. While data on surface water use and storage levels in reservoirs are easily accessible throughout the year, the impact on groundwater storage at the provincial scale has not been evaluated yet. However, lack of monitoring boreholes, discontinuous measurements, unavailable monitoring data, and installation of boreholes without proper licensing has made it difficult to manage groundwater sustainably in the region. Remote sensing from National Aeronautics and Space Administration’s Gravity Recovery and Climate Experiment (GRACE) provides continuous and freely accessible datasets through which trends and variations in groundwater storage can be estimated. This research aims to understand how GRACE and Global Land Data Assimilation System (GLDAS) data can be used to monitor groundwater storage in the Western Cape. In-situ groundwater storage declined prominently in the Western Cape during droughts (2003-2006, 2009-2011, 2015-2018 and 2017-2019). While some aquifers are recovering, others (e.g., Vanhynsdorp Aquifer) are still declining, possibly from over-abstraction for irrigation. GRACE TWS (JPL-M) anomalies showed positive moderate correlation (r = 0.69) with in-situ groundwater measurements from the Adelaide Subgroup Aquifer possibly because of the unit’s large areal extent, unconfined nature, and large groundwater storage fluctuations. While the Table Mountain Group Upper Aquifer Unit (TMG UAU) and Cape Flats Aquifer both showed significant positive correlations with GLDAS CLSM (catchment land surface model) groundwater storage of 0.83 and 0.73, respectively; possibly because they are unconfined and their fast response to precipitation. GRACE TWS anomalies have the potential to monitor groundwater storage of the Adelaide Subgroup Aquifer, while GLDAS CLSM groundwater storage data has the potential to monitor groundwater storage of the unconfined TMG UAU and Cape Flats Aquifer. GRACE and GLDAS CLSM groundwater storage data have the potential to monitor groundwater in other parts of South Africa or data scarce regions of Africa to ensure that future generations have access to groundwater.en_ZA
dc.description.abstractAFRIKAANSE OPSOMMING: Die Wes-Kaap is 'n waterskaars provinsie van Suid-Afrika en het oor die laaste paar dekades meer aangewese geraak op grondwater as gevolg van gereelde droogtes, wat na verwagting in die toekoms sal vererger. Terwyl data oor oppervlakwatergebruik en bergingsvlakke in reservoirs deur die jaar maklik toeganklik is, is die impak op grondwaterberging op provinsiale skaal nog nie geëvalueer nie. Gebrek aan monitering van boorgate, diskontinue metings, onbeskikbare moniteringsdata en installering van boorgate sonder behoorlike lisensiëring het dit egter moeilik gemaak om grondwater volhoubaar in die streek te bestuur. Afstandwaarneming van Nasionale Lugvaartkunde en Ruimte-administrasie se Gravity Recovery and Climate Experiment (GRACE) verskaf deurlopende en vrylik toeganklike datastelle waardeur tendense en variasies in grondwaterberging beraam kan word. Hierdie navorsing het ten doel om te verstaan hoe GRACE en Global Land Data Assimilation System (GLDAS) data gebruik kan word om grondwaterberging in die Wes-Kaap te monitor. In-situ grondwaterberging het prominent afgeneem in die Wes-Kaap tydens droogtes (2003-2006, 2009-2011, 2015-2018 en 2017-2019). Terwyl sommige waterdraers besig is om te herstel, neem ander (bv. Vanhynsdorp Akwifeer) steeds af, moontlik van ooronttrekking vir besproeiing. GRACE TWS (JPL-M) anomalieë het positiewe matige korrelasie (r = 0.69) getoon met in-situ grondwatermetings van die Adelaide Subgroep Akwifeer moontlik as gevolg van die eenheid se groot oppervlakte omvang, onbeperkte aard en groot grondwaterbergings fluktuasies. Terwyl die Tafelberggroep Boonste AkwifeerEenheid (TMG UAU) en Kaapse Vlakte Akwifeer albei betekenisvolle positiewe korrelasies met GLDAS CLSM (opvanggebied landoppervlak model) grondwaterberging van onderskeidelik 0.83 en 0.73 getoon het; moontlik omdat hulle onbeperk is en hul vinnige reaksie op neerslag. GRACE TWS-afwykings het die potensiaal om grondwaterberging van die Adelaide Subgroep Akwifeer te monitor, terwyl GLDAS CLSM grondwaterberging data die potensiaal het om grondwaterberging van die onbeperkte TMG UAU en Kaapse Vlakte Akwifeer te monitor. GRACE en GLDAS CLSM grondwaterbergings data het die potensiaal om grondwater in ander dele van Suid-Afrika of dataskaars streke van Afrika te monitor om te verseker dat selfs toekomstige generasies toegang tot grondwater het.af_ZA
dc.description.versionMastersen_ZA
dc.format.extentxii, 151 pages : illustrations (some color), mapsen_ZA
dc.identifier.urihttp://hdl.handle.net/10019.1/127069
dc.language.isoen_ZAen_ZA
dc.publisherStellenbosch : Stellenbosch Universityen_ZA
dc.rights.holderStellenbosch Universityen_ZA
dc.subject.lcshGroundwater -- South Africa -- Western Capeen_ZA
dc.subject.lcshGroundwater -- Evaluationen_ZA
dc.subject.lcshGroundwater -- Storage -- Monitoringen_ZA
dc.subject.lcshGravity Recovery and Climate Experimenten_ZA
dc.subject.lcshGroundwater -- Effect of drought onen_ZA
dc.subject.lcshGlobal Land Data Assimilation Systemen_ZA
dc.subject.lcshGroundwater -- Quality -- South Africa -- Western Capeen_ZA
dc.subject.nameUCTDen_ZA
dc.titleEvaluating groundwater storage changes under drought in the Western Cape using satellite and in-situ dataen_ZA
dc.typeThesisen_ZA
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