Solar influences on hydrological processes in South Africa

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dc.contributor.advisorDu Plessis, Jakobus Andriesen_ZA
dc.contributor.authorBowmaker, Alan Philip Macgowanen_ZA
dc.contributor.otherStellenbosch University. Faculty of Engineering. Dept. of Civil Engineering.en_ZA
dc.date.accessioned2024-02-20T13:05:08Zen_ZA
dc.date.accessioned2024-04-26T17:32:35Zen_ZA
dc.date.available2024-02-20T13:05:08Zen_ZA
dc.date.available2024-04-26T17:32:35Zen_ZA
dc.date.issued2024-03en_ZA
dc.descriptionThesis (MEng)--Stellenmbosch University, 2024.en_ZA
dc.description.abstractENGLISH ABSTRACT: South African water resources play a vital role in the well-being of the country. The deeper understanding of the complex mechanisms that influence the decadal variability of hydrological processes is both needed and beneficial. With firm knowledge of the terrestrial systems that impact hydrological processes on hourly to annual bases already established, insufficient understanding of the extra-terrestrial forces that influence decadal hydrological variability in South Africa is evident. Therefore, examining the existence and extent of a relationship between decadal periodic solar activity and South African hydrological processes is necessary. This relationship has been investigated on a global scale, with the use of various methodologies, with no unanimous conclusions being drawn between different studies. This research aimed to ascertain if an observable relationship existed between solar activity and the occurrences of above and below average hydrological processes in South Africa. The research aim is achieved by investigating if a greater proportion of historical hydrological above average events, defined by the 99th percentile, occurred during lowered solar activity, defined by the sunspot number. Data is collected on the daily sunspot number and long term streamflow volumes, rainfall depths, flood peaks and daily rainfall depths from 1900 to 2022. The above average hydrological events, after quality analysis, are defined using the 99th percentile and analysed on an instantaneous, monthly and annual time basis to ensure all observable facets of the relationship were investigated. The difference in time between the occurrence of identified above average hydrological events and sunspot minimum is calculated, and termed the Lag-time, for the entire study period and for individual solar cycles. The cumulative sum of normalised hydrological events is plotted to depict when within individual solar cycles, abrupt changes in the accumulated magnitude of events occur. This research found that the occurrence of above average flood peaks and monthly and annual streamflow volumes occurred more often during the sunspot minimum. However, the inspection of individual solar cycles revealed inconsistency in observed flood peak and streamflow Lag-times and cumulative sums over the study period. Over the study period, increased daily rainfall depths are observed to occur less during the sunspot minimum. Increased total monthly and annual rainfall depths are observed to occur more often during the sunspot minimum, yet not as significantly as exhibited by the flood peaks and streamflow volumes. Similarly, inconsistency in the occurrence of rainfall events within individual solar cycles is observed. Overall, the existence of a relationship between solar activity and hydrological processes exists and appears to possess a stronger influence over decadal streamflow compared to rainfall. The annual average sunspot number can be used as an indication that above average floods and extreme rainfall events have a greater probability of occurring during the sunspot minimum.en_ZA
dc.description.abstractAFRIKAANSE OPSOMMING: Suid-Afrikaanse waterbronne speel 'n belangrike rol in die welstand van die land. 'n Dieper begrip van die komplekse meganismes wat dekadelange variasies in hidrologiese prosesse beïnvloed, is sowel nodig as voordelig. Alhoewel kennis van die aardse stelsels wat hidrologiese prosesse op 'n uurlikse tot jaarlikse basis beïnvloed reeds gevestig is, is daar 'n onvoldoende begrip van die buite-aardse kragte wat dekadelange hidrologiese variasie in Suid-Afrika beïnvloed. Daarom is dit noodsaaklik om die bestaan en omvang van 'n verband tussen dekadelange periodieke sonaktiwiteit en Suid-Afrikaanse hidrologiese prosesse te ondersoek. Hierdie verhouding is op 'n globale skaal ondersoek, met behulp van verskeie metodes, sonder dat daar eenstemmige gevolgtrekkings tussen verskillende studies is. Hierdie navorsing het beoog om te bepaal of 'n waarneembare verhouding bestaan tussen sonaktiwiteit en die voorkoms van bo- en ondergemiddelde hidrologiese prosesse in Suid-Afrika. Die navorsingsdoelwit is bereik deur ondersoek in te stel of 'n groter verhouding van historiese hidrologiese gemiddelde gebeurtenisse, omskryf deur die 99ste persentiel, voorgekom het tydens laer sonaktiwiteit, omskryf deur die sonkolgetal. Data is ingesamel oor die daaglikse sonkolgetal en langtermynstroomvolumes, reënval, vloedpieke en daaglikse reënval vanaf 1900 tot 2022. Die bogemiddelde hidrologiese gebeurtenisse, na gehalte-ontleding, is omskryf met behulp van die 99ste persentiel en is op 'n oombliklike, maandelikse en jaarlikse tydbasis ontleed om te verseker dat alle waarneembare aspekte van die verhouding ondersoek is. Die verskil in tyd tussen die voorkoms van geïdentifiseerde bogemiddelde hidrologiese gebeurtenisse en die sonkolminimum word bereken en as die 'wag-tyd' vir die hele studietydperk en vir individuele sonkringe bepaal. Die kumulatiewe som van genormaliseerde hidrologiese gebeurtenisse word uitgestip om aan te toon wanneer individuele sonsiklusse skielike veranderinge in die kumulatiewe omvang van gebeurtenisse ondervind. Hierdie navorsing het gevind dat die voorkoms van bogemiddelde vloedpieke en maandelikse en jaarlikse stroomvolumes meer gereeld gedurende die sonkolminimum plaasgevind het. Die inspeksie van individuele sonsiklusse het egter inkonsekwente resultate gelewer vir vloedpiek, stroomvloei wagtydperke en kumulatiewe totale oor die studietydperk. Dit word waargeneem dat daaglikse reën minder voorkom gedurende die sonkolminimum oor die studietydperk. Die totale uiterste maandelikse en jaarlikse reën word meer gereeld gedurende die sonkolminimum waargeneem, maar nie so beduidend soos deur die vloedpieke en stroomvolumes uitgebeeld nie. ‘n Soortgelyke ongelykheid in die voorval van reën gebeurtenisse binne individuele sonsiklusse word waargeneem. Daar bestaan dus 'n verhouding tussen sonaktiwiteit en hidrologiese prosesse en dit blyk asof dit 'n sterker invloed op dekadelange stroomvloei het as op reënval. Die jaarlikse gemiddelde sonkolgetal kan as 'n aanduiding gebruik word dat bogemiddelde vloede en uitermate hoe reenval gebeurtenisse 'n groter waarskynlikheid het om gedurende die sonkolminimum voor te kom.af_ZA
dc.description.versionMastersen_ZA
dc.format.extentxiv, 213 pages : illustrationsen_ZA
dc.identifier.urihttps://scholar.sun.ac.za/handle/10019.1/130436
dc.language.isoen_ZAen_ZA
dc.language.isoen_ZAen_ZA
dc.publisherStellenbosch : Stellenbosch Universityen_ZA
dc.rights.holderStellenbosch Universityen_ZA
dc.subject.lcshSolar activity -- South Africaen_ZA
dc.subject.lcshStreamflow -- South Africaen_ZA
dc.subject.lcshSunspots -- South Africaen_ZA
dc.subject.lcshWater-supply -- South Africaen_ZA
dc.titleSolar influences on hydrological processes in South Africaen_ZA
dc.typeThesisen_ZA
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