Manual on pumping test analysis in fractured rock aquifers
| dc.contributor.advisor | Van Tonder, G. J. | |
| dc.contributor.author | Van Bosch, Izak Jacobus | |
| dc.date.accessioned | 2017-11-06T10:27:12Z | |
| dc.date.available | 2017-11-06T10:27:12Z | |
| dc.date.issued | 2000-11 | |
| dc.description.abstract | English: With the depletion of surface water resources in South Africa the utilisation of groundwater as the only potable water resource for communities in some rural areas is quickly becoming a reality. Failure of this resource will cause serious problems and it may even lead to loss of life. To prevent failure and to ensure the sustainability of this new resource, pumping tests are performed to determine the long-term sustainable yield of bore hole. This is the main reason why pumping tests are performed in South Africa, but in some instances pumping tests are performed to determine parameter values for aquifers. This research focussed on presenting guidelines on the proper planning and execution of the different types of pumping tests. To perform a proper pumping test involves big financial costs and therefor it is important to ensure that the correct information is obtained during such a test. Recommendations regarding the lengths of pumping tests as well as the abstraction rates during pumping tests are also made in this research. Before the interpretation of pumping test data it is important to obtain a better understanding of the basic concepts and characteristics involved in groundwater hydraulics. These concepts, together with the interpretation of diagnostic and derivative data plots are discussed in detail and it will provide the reader with enough knowledge to identify and understand the different flow regimes present in an aquifer. This research looks at the different steps involved in the interpretation of pumping test data and these steps are illustrated by means of worked examples. The different analytical methods to determine parameter values for an aquifer are also discussed in this thesis and the assumptions made in developing these methods are pointed out to the reader. In most cases these assumptions result in incorrect parameter value estimates. Numerical models, developed for the unique aquifer systems of South Africa, yielding the correct parameter values, are also discussed. Well losses can be divided into linear and non-linear losses. Non-linear well losses are mainly caused by turbulent flow inside the aquifer and borehole. This research however shows a non-linear relationship between drawdown and abstraction rate while the flow inside the aquifer is still linear. The non-linearity between drawdown and abstraction rate is corroborated by means of several examples and this nonlinearity can only be the result of the unique composition of aquifers in this country. Different abstraction rates result in different fractures being dewatered and fracture extents that are reached, causing a smaller effective T-value. The consequence of this non-linearity is that it is very difficult to extrapolate the future water levels in an aquifer. To estimate a sustainable yield in the case of non-linearity this research recommends a revised step drawdown test. This l00-minute test, conducted without constant time intervals, will also point out the positions of the main water strikes. A method, developed in South Africa, with which the long-term sustainable yield can be determined, is also discussed in detail and it is explained by means of a step by step worked example. Included in this method is the effect of boundary conditions as well as a risk analysis. | en_ZA |
| dc.description.abstract | Afrikaans: Met die uitputting van oppervlak waterbronne in Suid-Afrika word die gebruik van grondwater bronne as die enigste bruikbare waterbron vir sommige landelike gemeenskappe 'n realiteit. Indien hierdie bron onvoldoende is, kan dit ernstige probleme en selfs lewensverlies tot gevolg hê. Om die swigting van boorgate te vehoed en om die volhoubaarheid van hierdie bron te verseker, word pomptoetse gedoen om die langtermyn lewerings van boorgate korrek te bereken. Dit is dan ook die hoof doelwit van die meeste pomptoetse wat in Suid-Afrika gedoen word, maar in sommige gevalle word pomptoetse ook gedoen om parameters vir akwifere te bepaal. Hierdie navorsing fokus op die onwikkeling van riglyne vir die behoorlike beplanning en uitvoering van die verskillende tipes pomptoetse. Groot kostes word aangegaan om pomtoetse uit te voer en daarom is dit belangrik dat akkurate inligting tydens so 'n pomptoets bekom word. Aanbevelings rondom die tydsduur van pomptoetse sowel as ontrekkingstempo 's tydens pomptoetse, word ook gemaak. Voordat pomptoetse ontleed word, is dit belangrik om 'n goeie kennis van die basiese begrippe en eienskappe wat by grondwater betrokke is, op te doen. Hierdie begrippe, saam met die ontleding van afgeleide grafieke word breedvoerig bespreek en dit sal die leser toerus met voldoende kennis om die verskillende vloeipatrone in akwifeer te kan identifiseer. Die navorsing kyk na die veskillende stappe wat by die ontleding van pomptoetse betrokke is en hierdie stappe word aan die hand van voorbeelde verduidelik. Die verskillende analitiese metodes wat gebruik word om parameters te bepaal, word ook bespreek en die aannames wat by die ontwikkeling van die verskillende metodes gemaak is, word uitgelig. In die meeste gevalle het hierdie aannames tot gevolg dat foutiewe parameter waardes verkry word. Numeriese metodes, wat vir die unieke akwifeer toestande in Suid-Afrika ontwikkel is en wat korrekte parameter waardes lewer, word ook bespreek. Boorgat verliese kan in lineêre en nie-lineêre verliese verdeel en nie-lineêre verliese is die gevolg van turbulente vloeie in die boorgat en akwifeer. Hierdie navorsing bewys egter dat daar 'n nie-lineêre verband tussen die afttrekking in die boorgat en die ontrekkingstempo bestaan, selfs al is die vloei in die boorgat en die akwifeer lineêr. Hierdie waarneming word met behulp van verskeie voorbeelde gestaaf Hierdie nielineariteit is die gevolg van die unieke samestelling van akwifere in Suid-Afrika. Verskillende ontrekkingstempo's het tot gevolg dat verskillende frakture ontwater word en in sommige gevalle word die einde van frakture bereik. Dit het tot gevolg dat die effektiewe T-waarde kleiner word. As gevolg van hierdie nie-lineariteit word die vooruitskatting van toekomstige watervlakke in akwifere bemoeilik. Om die volhoubare lewering in die geval van nie-lineariteit te bereken, word 'n hersiene staptoets in die navorsing aanbeveel. Hierdie l00-minuut toets, waarvan die tydsintervalle nie gelyk hoefte wees nie, salook die posisies van die hooffrakture aandui. 'n Metode wat in Suid-Afrika ontwikkel is en wat gebruik word om die langtermyn volhoubare lewering van 'n boorgat te bereken, word volledig bespreek. Die metode word aan die hand van 'n uitgewerkte voorbeeld verduidelik. Ingesluit in die metode is die uitwerking van grenstoestande sowel as 'n risiko analise. | af |
| dc.description.sponsorship | Department of Water Affairs and Forestry | en_ZA |
| dc.identifier.uri | http://hdl.handle.net/11660/7423 | |
| dc.language.iso | en | en_ZA |
| dc.publisher | University of the Free State | en_ZA |
| dc.rights.holder | University of the Free State | en_ZA |
| dc.subject | Pumping test analysis | en_ZA |
| dc.subject | Double porosity systems | en_ZA |
| dc.subject | Parameter estimation | en_ZA |
| dc.subject | Long term sustainable yield calculation | en_ZA |
| dc.subject | Abstraction rate | en_ZA |
| dc.subject | Available drawdown | en_ZA |
| dc.subject | Length of pumping tests | en_ZA |
| dc.subject | Non-linearity between drawdown and abstraction rate | en_ZA |
| dc.subject | Two-dimensional numerical model | en_ZA |
| dc.subject | Revised step drawdown test | en_ZA |
| dc.subject | Aquifers -- Measurement | en_ZA |
| dc.subject | Groundwater flow -- Measurement | en_ZA |
| dc.subject | Groundwater | en_ZA |
| dc.subject | Dissertation (M.Sc. (Geodhydrology))--University of the Free State, 2000 | en_ZA |
| dc.title | Manual on pumping test analysis in fractured rock aquifers | en_ZA |
| dc.type | Dissertation | en_ZA |