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A revision of evaporation and pan factors in use in South Africa
Thesis (MEng)--Stellenbosch University, 2023.
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| Format: | Thesis |
| Language: | en_ZA en_ZA |
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Stellenbosch : Stellenbosch University
2023
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| _version_ | 1867613894819708928 |
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| access_status_str | Open Access |
| author | Taljaard, Carl Magnus Lönngren |
| author2 | Du Plessis, Jakobus Andries |
| author_browse | Du Plessis, Jakobus Andries Taljaard, Carl Magnus Lönngren |
| author_facet | Du Plessis, Jakobus Andries Taljaard, Carl Magnus Lönngren |
| author_sort | Taljaard, Carl Magnus Lönngren |
| collection | Thesis |
| dc_rights_str_mv | Stellenbosch University |
| description | Thesis (MEng)--Stellenbosch University, 2023. |
| format | Thesis |
| id | oai:scholar.sun.ac.za:10019.1/127336 |
| institution | Stellenbosch University (South Africa) |
| language | en_ZA en_ZA |
| last_indexed | 2026-06-10T12:43:24.214Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from SUNScholar — Stellenbosch University Repository |
| publishDate | 2023 |
| publishDateRange | 2023 |
| publishDateSort | 2023 |
| publisher | Stellenbosch : Stellenbosch University |
| publisherStr | Stellenbosch : Stellenbosch University |
| record_format | dspace |
| source_str | SUNScholar — Stellenbosch University Repository |
| spelling | oai:scholar.sun.ac.za:10019.1/127336 A revision of evaporation and pan factors in use in South Africa Taljaard, Carl Magnus Lönngren Du Plessis, Jakobus Andries Stellenbosch University. Faculty of Engineering. Dept. of Civil Engineering. Evaporation, pan factors Pan evaporation Thesis (MEng)--Stellenbosch University, 2023. ENGLISH ABSTRACT: South Africa is an arid country where water is a valuable and scarce resource. The management of this resource, and the quantifying and mitigation of the losses from the large reservoirs are of paramount importance. Open water evaporation is responsible for large losses from reservoirs, and it is thus important to have a firm understanding of this phenomenon to effectively plan and manage water resources. The understanding of evaporation also plays a vital role in agriculture. This research aims to report on evaporation trends and revise certain aspects of evaporation in South Africa. The relationship between S-pan and A-pan evaporation, as well as the pan coefficients (used to estimate open water evaporation) currently in use in South Africa, is severely outdated and in need of updating, especially as evaporation changes over time. Various analyses were completed by utilising daily data sets pertaining to evaporation and large reservoirs. Data limitations constrained this research to a great extent, but valuable insights were gained. To gain a holistic understanding of evaporation in a South African context, this research had three main goals: • Performing trend analyses of S-pan evaporation over various time periods. • Updating the relationship between S-pan and A-pan evaporation. • Updating pan coefficients used to determine open water evaporation. The S-pan trends were determined for 30-year, 60-year and longer-term periods to compare the rates of change over various time periods. The data was compiled into daily, monthly, annual, individual monthly (daily and monthly) and seasonal (daily and monthly) data sets, and the trends for each of these formats were determined. Overall, declining trends dominated each of the analyses, but no consistent patterns or clear shifts could be detected. The relationship between S-pan and A-pan evaporation was found to be linear in each of the various tested formats. This part of the research was done in daily, monthly, annual and individual monthly contexts, determining new equations to estimate pan evaporation values for one type of evaporation pan from observed pan evaporation values of the other type of evaporation pan. Station-specific and general equations were generated and tested for accuracy, comparing the results to those of the existing equations. It was found that the existing annual equations are still applicable, but new monthly equations, which are applicable to any evaporation station, are proposed. The availability of good quality data limited the research on pan coefficients used to determine evaporation from the large reservoirs in South Africa to a great extent. The evaporation losses from five reservoirs in South Africa were determined for periods where the dams had no form of inflow, and new pan coefficients were calculated for this limited scope. On comparison, it was found that the current pan coefficients are still viable. This research indicates that an overall decline in evaporation rates was observed over time. It is recommended that the data availability and quality concerns highlighted in this research be addressed, and this research repeated – perhaps by using different means of determining evaporation – to gain a full understanding of evaporation in South Africa without the severe limitations experienced during this research. AFRIKAANS OPSOMMING: Suid-Afrika is ‘n droë land waar water ‘n waardevolle en skaars hulpbron is. Die bestuur van dié hulpbron, en die kwantifisering en vermindering van die verliese van die groot reservoirs is van uiterste belang. Oopwaterverdamping is verantwoordelik vir groot verliese in reservoirs, en dit is belangrik om ‘n grondige begrip van hierdie verskynsel te hê om sodoende waterhulpbronne doeltreffend te beplan en te bestuur. ‘n Begrip van wat verdamping behels, speel ook ‘n deurslaggewende rol in die landbou. Hierdie navorsing poog om verdampingstendense beter te verstaan en sommige aspekte van verdamping in Suid-Afrika te hersien. Verskeie ontledings is gedoen deur datastelle, wat van toepassing is op verdamping en groot damme, aan te wend. Databeperkings het hierdie studie tot ‘n groot mate beperk, maar waardevolle insigte is verkry. Om ‘n holistiese begrip van verdamping in Suid- Afrika te kry, het die navorsing drie hoof doelwitte gehad: • Om tendense van S-pan-verdamping oor verskillende periodes te bepaal. • Die verhouding tussen S-pan- en A-pan-verdamping by te werk. • Om pan-koëffisiënte, wat gebruik word om oopwaterverdamping vas te stel, by te werk. Die S-pan-tendense is bepaal vir 30-jaar, 60-jaar en langertermyn-tydperke om die tempo van verandering oor verskillende tydperke vas te stel. Die data is saamgestel in daaglikse, maandelikse, jaarlikse, individueel-maandelikse (daaglikse en maandelikse) en seisoenale (daaglikse en maandelikse) datastelle, en die tendense vir elkeen van hierdie formate is bepaal. Oor die algemeen, het dalende tendense elkeen van hierdie ontledings gedomineer, maar geen konsekwente patrone of duidelike veranderings kon waargeneem word nie. Die verhouding tussen S-pan- en A-pan-verdamping is in elkeen van die verskillende getoetste formate lineêr bevind. Hierdie deel van die navorsing is in daaglikse, maandelikse, jaarlikse en individueel-maandelikse kontekste gedoen, wat nuwe vergelykings om panverdampingswaardes vir een tipe verdampingspan vanaf waargeneemde panverdampingswaardes van die ander tipe verdampingspan te bepaal. Stasie-spesifieke en algemene vergelykings is bepaal en getoets vir akkuraatheid deur die resultate met dié van die bestaande vergelykings te vergelyk. Dit is bevind dat die bestaande jaarlikse vergelykings steeds geldig is, maar nuwe maandelikse vergelykings, wat op enige verdampingstasie van toepassing is, word voorgestel. Masters 2023-03-07T08:15:01Z 2023-05-18T07:16:45Z 2023-03-07T08:15:01Z 2023-05-18T07:16:45Z 2023-03 Thesis http://hdl.handle.net/10019.1/127336 en_ZA en_ZA Stellenbosch University xvi, 171 pages : illustrations. application/pdf Stellenbosch : Stellenbosch University |
| spellingShingle | Evaporation, pan factors Pan evaporation Taljaard, Carl Magnus Lönngren A revision of evaporation and pan factors in use in South Africa |
| title | A revision of evaporation and pan factors in use in South Africa |
| title_full | A revision of evaporation and pan factors in use in South Africa |
| title_fullStr | A revision of evaporation and pan factors in use in South Africa |
| title_full_unstemmed | A revision of evaporation and pan factors in use in South Africa |
| title_short | A revision of evaporation and pan factors in use in South Africa |
| title_sort | revision of evaporation and pan factors in use in south africa |
| topic | Evaporation, pan factors Pan evaporation |
| url | http://hdl.handle.net/10019.1/127336 |
| work_keys_str_mv | AT taljaardcarlmagnuslonngren arevisionofevaporationandpanfactorsinuseinsouthafrica AT taljaardcarlmagnuslonngren revisionofevaporationandpanfactorsinuseinsouthafrica |