Vermeulen, P. D.Prinsloo, Martiens2018-01-112018-01-112005-02http://hdl.handle.net/11660/7575English: External factors that influence the aquifer characteristics of, and sustainable yield from, the dolomitic aquifer include topography, rainfall, surface drainage, evapotranspiration, plant growth, geology, and soils. The topography is gently undulating with a gradient of between 1:400 and 1:800. The low topographical gradients inhibit surface run-off and promote high recharge rates. The annual rainfall will provide the volume of water present in the catchment area that is available for potential recharge to the aquifer. The average rainfall is 1 115mm/annum. Water that leaves the hydrological system of the study area as surface run-off impacts on the volume of water available for recharge to the aquifer in the area. Despite the high rainfall volume and high rainfall intensity only one perennial surface run-off structure exists in the study area. The Kafue River is on average 10 to 20m wide and 3m deep. Only one non-perennial surface run-off feature exists. This feature feeds into the Ipumbu Dam. The volume of water that evaporates from the soil and vegetation before it can reach the underlying aquifer will impact on the volume of water that can be abstracted from the aquifer without negatively impacting on the volume of water in storage in the aquifer. Very little evaporation data is available for the study area. Comparing the calculated potential total evaporation volume with the measured net evaporation and annual rainfall indicates a discrepancy between the evaporation and rainfall data. The rainfall data is considered to be accurate, and based on perceived inaccuracy of the evaporation data, it is recommended that the evaporation data not be used in water balance calculations. The natural plant growth influences the evapotranspiration and in some cases the surface run-off characteristics. Brachystegia Miombo woodlands cover the study area with areas of widespread grass cover between the trees. The main aquifer consists of Upper Roan Formation limestone and dolomite. The main joint set (160º strike direction) controls the strike direction of the solution cavities in the area. Schist and quartzite of the Lower Roan Formation border the limestone and dolomite. Extensive fracturing in the dolomite is found in the geological logs of the high yielding boreholes drilled in the area. The soil in the study area displays infiltration rates higher than the observed rainfall intensity. Combined with the low topographical gradients that retard run-off the high infiltration rate leads to high recharge percentages. The aquifer hydraulic characteristics were determined during the investigation. It is considered that Lake Nampamba forms part of an extensive, well-connected solution cavity network. No compartmentalisation of the dolomite is evident. Three prominent karstic features (Lake Nampamba, Lake Kashiba and the “Chibili Pavement”) occur in the area. Both Lake Nampamba and Lake Kashiba are sinkholes in the dolomite. The author has no scientific evidence to conclude that the solution cavity network stretches as far as the Kafue River. However, analysis of the water level, abstraction and water level data does confirm that Lake Nampamba in the east and the dambo areas in the west that feed Ipumbu dam are interconnected. The groundwater displays a calcium-magnesium dominant character, as is expected from a dolomitic aquifer. Plotting the chemistry data on a trilinear (Piper) diagram indicates that the groundwater recently recharged. This corresponds to the theory of high recharge due to the relatively high rainfall, flat topography, and high soil infiltration rate. Depth to groundwater varies on a seasonal basis due to fluctuations in rainfall and thus recharge, and abstraction volumes. The groundwater level shows an immediate response to recharge, but does indicate a one to two month delay between maximum rainfall and peak groundwater level. A total of 65 boreholes were drilled in the study area between 1978 and 2004. Preliminary aquifer tests were performed on 38 boreholes, and 14 boreholes were identified as high yielding boreholes. Constant rate aquifer tests were performed on these boreholes. The aquifer test data was analysed to obtain the aquifer transmissivity. The aquifer transmissivity ranges between 1 and 6 900m2/day. This wide range is expected in karstic aquifers where the high transmissivity is associated with solution cavities and fractured areas. The low transmissivities are associated with the fine crystalline, competent, unweathered rock. Sustainable yields from the borehole calculated from the aquifer test data range between 5 and 100l/s (432 and 8 640m3/day). Recharge calculations were performed using the Chloride, SVF, Equal Volume and CRD methods. The chloride method is used only as an indication of the recharge percentage. The SVF, Equal Volume, and CRD methods calculated recharge as 25% of the annual rainfall. Aquifer storativity is calculated using the SVF and CRD methods at 0.02 (2%). The total volume of water that can be abstracted from the combined eastern and western aquifers is calculated to be 136Mm3/annum. The current and proposed future annual abstraction volumes are 25.3Mm3 and 44.42Mm3 respectively. This indicates that the combined eastern and western aquifers are capable of sustaining the abstraction volumes. A numerical model was constructed to evaluate the assumptions made, and correlates the calculated values of the manual calculations. The model was initially constructed in steady state without taking the abstraction from the aquifer into account. Once the model was successfully calibrated, the abstraction volumes were incorporated into the numerical model and the model was further calibrated against time series observed rainfall, groundwater levels and abstraction volumes by comparing the groundwater levels with time against those calculated using the numerical model. Once the model was calibrated, the model was applied to evaluate the sustainability of the current and proposed abstraction programs. The numerical model confirms that the combined eastern and western aquifers are capable of sustaining the abstraction programs.Afrikaans: Die eksterne faktore wat die eienskappe en volhoubare onttrekking van die dolomitiese akwifeer in die Koperbelt Provinsie beïnvloed sluit in topografie, reënval, oppervlak afloop, evapotransprasie, plantergroei, geologie en grond. Die topografie is golwend met ‘n gradiënt van tussen 1:400 en 1:800. Die lae gradiënt beperk oppervlak afloop van water en bevorder insypeling van water in die grond in. Die jaarlikse reënval voorsien die hoeveelheid water wat beskikbaar is in die opvang gebied vir potensiële aanvulling tot die akwifeer. Die gemiddelde jaarlikse reënval word bereken as 1 115mm/jaar. Die volume water wat die sisteem verlaat as oppervlak afloop beïnvloed die volume water wat beskikbaar sal wees vir aanvulling tot die akwifeer. Ten spyte van die hoë reënval volumes en reënval intensiteit bestaan daar slegs een standhoudende rivier in die omgewing. Die Kafuerivier is gemiddeld 10 tot 20m breed en 3m diep. Slegs een niestandhoudende rivier bestaan in die gebied. Die hoeveelheid water wat verdamp van die plantegroei en grond voordat dit die onderliggende akwifeer kan bereik, sal die volume water wat volhoubaar onttrek kan word beïnvloed. Baie min evaporasie data is beskikbaar vir die studie area. ‘n Vergelyking tussen die berekende potensiële totale evaporasie, netto evaporasie en reënval dui op onakkuraatheid van sommige van die data. Die reënval data word beskou as relatief akkuraat en gebasseer op die oënskynlike onbetroubaarheid van die evaporasie data word dit aanbeveel dat die evaporasie data nie gebruik word in water balans berekeninge nie. Die natuurlike plantegroei sal die evapotranspirasie en in sommige gevalle die oppervlak afloop eienskappe beïnvloed. Brachystegia Miombo woude kom voor in die studie gebied, met wydverspreide grasvelde tussen in. Die hoof akwifeer bestaan uit die Boonste Roan Formasie dolomiet en kalksteen. Die hoof naatstelsel strek in die rigting 160º en beheer ook die strekking van die ondergrondse oplossings holtes. Skis en kwartsiet van die Laer Roan Formasie grens aan die dolomiet en kalksteen. Goed ontwikkelde krake en nate word gevind in die geologiese profiele van die hoë lewering boorgate. Die grond in die studie area besit infiltrasie eienskappe wat hoër is as die reënval intensiteit van die area. Gekombineerd met die lae topografiese gradiënt gee die grond se infiltrasie tempo aanleiding tot hoë grondwater aanvullings waardes vir die akwifeer. Die hidroliese eienskappe van die akwifeer is bepaal tydens die studie. Lake Nampamba maak deel uit van ‘n wye, goed ontwikkelde netwerk van oplossings holtes in die dolomiet. Daar is geen bewys van kompartementalisasie van die dolomiet nie. Beide Lake Nampamba en Lake Kashiba is sinkgate wat in die dolomiet ontwikkel het. Die skrywer het geen wetenskaplike bewys gevind dat die oplossings netwerk tot by die Kafuerivier strek nie. Analise van reënval, grondwater vlakke en grondwater onttrekking volumes dui egter daarop dat die dolomitiese akwifeer in die ooste geassosieer met Lake Nampamba, en die dambo areas in die weste wat Ipumbu Dam voed, hidrolies verbind is. Die grondwater het ‘n kalsium – magnesium dominante karakter, soos verwag in ‘n dolomitiese area. ‘n Piper diagram plot dui op onlangse aanvulling tot die akwifeer. Dit stem ooreen met die teorie van hoë aanvulling tot die akwifeer as gevolg van relatiewe hoë reënval, plat topografie en hoë grond infiltrasie tempos. Die diepte tot die grondwater vlak varieër op ‘n seisoenale basis as gevolg van fluktuasies in reënval, en dus aanvulling tot die akwifeer, en onttrekkings volumes. Die grondwater vlakke toon ‘n onmiddelike reaksie op reënval en aanvulling tot die akwifeer, maar ‘n een tot twee maande tussenpose tussen maksimum reënval en maksimum grondwater vlakke. ‘n Totaal van 65 boorgate is tussen 1978 en 2004 in die area geboor. Voorlopige akwifeer toetse is op 38 van die boorgate uitgevoer en 14 boorgate is geidentifiseer wat moontlik hoë lewering gate kon wees. Konstante abstraksie tempo toetse is op hierdie 14 boorgate uitgevoer. Die pomp toets data is ontleed om die transmissiwiteit van die akwifeer te bepaal. Die akwifeer transmissiwiteit varieër tussen 1 en 6 900m2/dag. Hierdie wye reeks is te verwagte in karst areas waar die hoë transmissiwiteite geassosieer word met die oplossings holtes of naatsones. Die lae transmissiwiteite word geassosieer met die fyn kristallyne, soliede, onverweerde gesteentes. Volhoubare lewerings van die boorgate varieer tussen 5 en 100l/sek (432 en 8 640m3/dag). Aanvulling persentasie berekeninge is uitgevoer gebasseer op die chloried-, SVF-, gelyke volume- en CRD-metodes. Die chloried-metode is slegs as ‘n aanduiding van die ordegrootte van die aanvullings persentasie gebruik. Die SVF-, gelyke volume- en CRDmetodes dui aan dat 25% van die reënval uiteindelik die grondwater aanvul. Die akwifeer storing is bereken as 0.02 deur die SVF en CRD metodes toe te pas. Die totale volume water wat gesamentlik uit die oostelike en westelike akwifere onttrek kan word is bereken as 136Mm3/jaar. Die huidige en voorgestelde toekomstige onttrekking beloop onderskeidelik 25.3Mm3/jaar en 44.42Mm3/jaar. Die gesamentlike oostelike en westelike akwifere kan dus die onttrekkings volumes te onderhou. ‘n Numeriese model is opgestel om die aannames wat gebruik is te evalueer en met die berekeninge soos bespreek in hoofstukke 2 en 3 te korreleer. Die model is aanvanklik opgestel sonder om die onttrekking vanuit die akwifeer in ag te neem. Na suksesvolle kalibrasie van die aanvanklike model, is abstraksie geinkorporeer en die model is verder gekalibreer. Tyd reeks reënval, grondwater vlak en onttrekking data is gebruik om die vlak van kalibrasie van die model te meet deur die geobserveerde grondwater vlakke met tyd te vergelyk met dit wat bereken is deur die numeriese model. Na die finale kalibrasie van die model is die model toegepas deur die volhoubaarheid van die huidige en toekomstige onttrekkings volumes te evalueer. Die numeriese model bevestig dat die gekombineerde oostelike en westelike akwifere in staat is om die onttrekkings programme te onderhou.enGeology, StratigraphicAquifers -- Zambia -- Copperbelt ProvinceDissertation (M.Sc. (Hydrogeology))--University of the Free State, 2004DissertationUniversity of the Free State