Masters Degrees (Geology)

Permanent URI for this collectionhttps://hdl.handle.net/10413/6622

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Catchment hydrological modelling using ArcSWAT : a study of the Ingula pumped storage scheme (IPSS) catchments, South Africa.
(2017) Ngubane, Zesizwe.; Demlie, Molla Bekele.
Abstract available in PDF file.
Characterisation of groundwater and surface water interaction in the eThekwini Metropolitan District, KwaZulu-Natal, South Africa.
(2021) Mtshali, Sphindile.; Demlie, Molla Bekele.
Abstract available in PDF.
Conventional hydrogeological, hydrochemical and environmental isotope study of the Sandspruit River Catchment, Berg River Basin, South Africa.
(2012) Naicker, Sivashni.; Demlie, Molla Bekele.
The Sandspruit River catchment, found within the heart of the Swartland region is infamous for wheat and wine production. Variable groundwater quality and low productivity is encountered within the folded and fractured Malmesbury Group aquifer, whilst the most productive and better quality groundwater is found within the Table Mountain Group sandstone. The Sandspruit catchment (a tributary of the Berg River) represents a drainage system, whereby saline groundwater with TDS up to 10870 mg/l, and EC up to 2140 mS/m has been documented. The catchment belongs to the winter rainfall region with precipitation seldom exceeding 400mm/yr, as such, groundwater recharge occurs predominantly from May to August. Recharge estimation using the catchment water-balance method, chloride mass balance method, and qualified guesses produced recharge rates between 8-70 mm/yr. To understand the origin, occurrence and dynamics of the saline groundwater, a coupled analysis of major ion hydrochemistry and environmental isotopes (δ¹⁸O, δ²H and ³H) data supported by conventional hydrogeological information has been undertaken. Research data were collected in three seasonal field sampling campaigns within the study catchment. These spatial and multi-temporal hydrochemical and environmental isotope data provided insight into the origin, mechanisms and spatial evolution of the groundwater salinity. These data also illustrate that the saline groundwater within the catchment can be attributed to the combined effects of evaporation, salt dissolution, and groundwater mixing. The geology together with the local and regional faults control the chemistry of the groundwater, whereby relatively fresh groundwater can be observed in certain direct recharge areas. The salinity of the groundwater tends to vary seasonally and evolves in the direction of groundwater flow. The stable isotope signatures further indicate two possible mechanisms of recharge; namely, (1) a slow diffuse type modern recharge through a relatively low permeability material as explained by heavy isotope signal and (2) a relatively quick recharge prior to evaporation from a distant high altitude source as explained by the relatively depleted isotopic signal and sub-modern to old tritium values. A conceptual hydrogeological model based on the hydrogeological, hydrochemical, and environmental isotope data was developed for the Sandspruit catchment. This model, together with statistical and groundwater quality analysis has lead to the development of a proposed local optimized monitoring scheme for the catchment.
A geological and hydrogeological study of the Shu Shu thermal springs, KwaZulu-Natal.
(2013) Gravelet-Blondin, Kent Royson.; Watkeys, Michael Keith.; Demlie, Molla Bekele.
The Shu Shu thermal springs are located in central KwaZulu-Natal in South Africa at an altitude of 250m above mean sea level at the bottom of the Tugela Valley. They have been investigated in an attempt to ascertain whether or not they possibly share a common origin with fifteen other springs which are located in a north-northwestern trending, 1000km long zone within the eastern interior of the country. They have also been studied to establish if they potentially represent a viable and sustainable geothermal energy resource that may be developed in the future. Isotope ratios confirm that the thermal springs are meteoric in origin, and are likely recharged within a 130km long band located to the west toward the Great South African Escarpment. These waters then descend vertically to a depth of approximately 1827m – 2153m, at which point the fractures along which they move close due to escarpment-associated confining pressure. It is a reduction in this self-same confining pressure along the coastal plain, which occurs due to the continual removal of overburden, which forces the thermal water to migrate toward the east along ever-more opening fractures. Due to a slightly elevated geothermal gradient of 3.1°C / 100m at depth, this groundwater reaches a temperature of approximately 75°C – 85°C as it traverses toward the Shu Shu thermal springs over a time period of > 61 years (at present). The geochemical signature of the Shu Shu thermal waters is derived through leaching from the basement rocks through which they pass, with elevated concentrations of Na, K, Ca, Mg, Fe, Al, Si, F, Sr and SO₄ detected. Once below the floor of the Tugela Valley, at a depth of approximately 990m, the thermal groundwater commences its ascent, likely along the west-southwest – east-northeast orientated thrusts and associated fractures of the Tugela Terrane of the Natal Metamorphic Province. However, the thermal waters abut against those brittle structures trending north-northwest – south-southeast, which are perpendicular to the axis of least principle compressive stress, and so are ultimately forced to rise within the Shu Shu thermal springs. Prior to surfacing, the temperatures of these waters drop to approximately 67°C as a result of natural, conductive cooling processes. However intermixing with shallow, cold groundwater, which is discernible through geochemical and isotopic variations, and atmospheric impacts, further cool the thermal waters to a surfacing temperature of approximately 50°C. Nevertheless, a binary cycle geothermal energy power plant remains a possibility. Although thermal efficiency and volume flow rate values are favourable, heat transfer values are low and require further investigation through exploratory drilling. Nevertheless, the establishment of a 400kW power plant, should it occur, will typically be sufficient to service 625 rural homes.
Geotechnical characterization and slope stability analyses of the Town Bush Valley, Pietermaritzburg, South Africa.
(2018) Singh, Keval.; Hingston, Egerton Daniel Christian.; Demlie, Molla Bekele.
The construction of settlements over zones of instability is increasing the impact of disasters across the world both in developed and developing nations. Many areas in the greater Pietermaritzburg region in South Africa, such as the Town Bush Valley, are prone to slope instability due to the terrain morphology and high intensity rainfall. This study has investigated the geotechnical conditions at the Town Bush Valley, in Pietermaritzburg. A geotechnical characterization of the Town Bush Valley has been undertaken in order to understand the geotechnical conditions prevailing on site. Furthermore, two critical slopes were selected for slope stability analyses to investigate the conditions under which failure would occur. The method of analyses chosen was the Morgenstern and Price method using the Rocscience, SLIDE software. The analyses involved a deterministic approach and a probabilistic approach. In the deterministic approach, all the input variables were considered as constant values. In the case of the probabilistic approach, the effective shear strength parameters were chosen as the random variables in order to account for their uncertainty. Prior to the analyses, sensitivity analysis was conducted in order to see the effect of the effective shear strength parameters, c´ and φ´, on the factor of safety. Various scenarios, including groundwater conditions and surcharge load, were considered during the analyses. Results from the site characterization show that the site is characterized by heterogeneous talus material, which is underlain at depth by shales of the Pietermaritzburg Formation and sandstones of the Vryheid Formation. Particle size analysis, Atterberg Limits Determination and consolidated-drained triaxial tests were undertaken on the talus material. The slope stability analyses show that the probabilistic approach presents a better insight into the assessment of the slope than a deterministic approach in accounting for the uncertainty in the geotechnical parameters. The random behaviour of the geotechnical parameters was quantified through various probabilistic functions. The various functions derived during probabilistic slope stability analyses, allowed for an assessment of the reliability of the data sets. Keywords/Phrases: Deterministic slope stability analysis; Phreatic surface; Probabilistic slope stability analysis; Random variables; Town Bush Valley
Hydrochemical characterisation of Northern KwaZulu-Natal historic coal mining districts, Northeastern South Africa.
(2018) Mduduma, Hlumela.; Demlie, Molla Bekele.
This M.Sc. dissertation reports the results of a hydrogeochemical study undertaken on historical coal mining districts of northern KwaZulu-Natal (KZN) Province, South Africa. The research catchment covers an area of about 12945 km2, located in the head waters of the Tugela River Basin or the uThukela Water Management Area (WMA). The main aim of the study was to assess the effectiveness of the rehabilitation undertaken by the South African Government on the various defunct/abandoned historical coal mines in northern KZN in improving surface water and groundwater quality in the region. Characterisation of surface water and groundwater water in terms of their interconnection, flow and hydrochemistry were undertaken. Primary (original data) and secondary data and information were collected, collated and analysed to understand the hydrogeochemical conditions of the region. The original data collected through a series of field campaigns within the study area, were complimented with secondary data from the Department of Water Affairs and Sanitation (DWS) monitoring programme, the KZN Groundwater Recourse Information Project (GRIP), the National Groundwater Archives (NGA) and borehole logs, hydrochemical and borehole yield data from various reports. The results of the study reveal that since the beginning of groundwater monitoring in 2010, the groundwater has been characterised by circumneutral waters. Time series EC, SO42- and Fe2+ data reveal no incongruities apart from a few episodes of elevated concentrations. Surface water hydrochemical analyses revealed peaks in EC coupled with low pH at varied sampling points which are presumed to be impacts from Acid Mine Drainage (AMD). Time series saturation states of groundwater with respect to calcite and dolomite indicate that groundwater remains oversaturated with respect to these minerals but under saturated with respect to gypsum as a result of carbonate AMD neutralization reactions. Trace metal data reveal no anomalous concentrations both in surface water and groundwater samples as a result of the circumneutral hydrogeochemical conditions. Major ion hydrochemical data show two main groundwater hydrochemical facies in the study area, namely most upstream boreholes are characterized by Na-Ca-HCO3-SO4 and most downstream boreholes are characterised by Ca-Mg-HCO3-SO4 hydrochemical water types. All surface water and groundwater samples have δD and δ18O isotopic values that plot on or below the Local and Global Meteoric Water Lines, indicating recharge from meteoric source with some evaporation mainly within the rehabilitated mine dumps. The detectible tritium signal in the shallow aquifers reflect recent active recharge taking place.
Hydrogeochemical and environmental isotope characterization of the CO₂ springs along the Bongwana Fault, its impact on fresh water resources and implications for carbon capture and storage (CCS) in South Africa.
(2018) Nkwane, Mzikayise.; Demlie, Molla Bekele.
Natural CO²-rich springs at the Bongwana area in Eastern South Africa emanate from three sites along an 80 km long North-South trending Bongwana Fault. The geological unit that outcrops along the extent of the Fault are the Dwyka Group rocks that are made up of mainly tillites and subordinate sandstones, shales and conglomerates. The objectives of this M.Sc. study is to characterize these CO²-rich springs and assess their impacts on shallow groundwater and surface water chemistry and consequently to understand the implication of a failed CCS facility. Groundwater and surface samples were collected both at CO² emission and CO²-free springs, boreholes and streams around the length of the studied fault zone for the analyses of major ions, trace elements and environmental isotopes. Additionally, specific electrical conductivity (EC), total dissolved solids (TDS), pH, temperature, dissolved oxygen (DO), redox potential (Eh), total alkalinity, CO³²- and HCO³- concentrations were determined onsite. The results indicate that all the travertine cone springs located near Umtamvuna River are characterized by Na-Ca-Mg-HCO3 water types, while boreholes from shallow groundwater and river samples show Ca-Na-Mg-HCO³ types. Stable isotope (δ18O and δ2H) composition of the travertine cone springs shows a major negative shift from the meteoric water lines with δ18O and δ2H values ranging from -7.78 to -6.52 ‰ and -21.5 to -17.9 ‰, respectively. While, the stable isotopic composition of shallow groundwater reflects local and modern meteoric recharge. These observations indicate that the reservoir and source of recharge for the deep circulating groundwater are different from the shallow groundwater. Based on onsite hydrogeological, hydrogeochemical, and environmental isotope observations, a hydrogeological conceptual model is proposed, which states that the groundwater recharge for deep circulating groundwater is to the west of the Bongwana fault, located at a higher altitude. From these altitudes, groundwater percolates through deep fractures and faults to greater depths. As groundwater percolates through the rock, it interacts with minerals and the initial recharge chemistry and isotopic composition is altered along the groundwater flow paths. At depth, groundwater dissolves carbonate rocks and as a result CO² is generated. The dissolution of CO² in groundwater further drives the leaching of the formation minerals along the flow path. Near the surface, CO² exsolves and travertine mainly composed of calcite, amorphous silica and iron hydroxides is formed. Geochemical inverse modelling and bivariate correlation among groundwater hydrochemical parameters for travertine springs indicate that the major geochemical processes that are responsible for the observed chemical composition are the dissolution of calcite, dolomite, Pyrite, Goethite, K-feldspars, fluorite, albite and sylvite and the precipitation of calcite, amorphous silica, iron hydroxide, iron carbonates, kaolinite and CO² gas. The carbonate minerals are attributed to the dissolution of carbonate rocks at depth. Feldspars are common from the Dwyka Group Diamictites, whereas the plagioclase feldspar (albite) is probably originating from the recharge area outside of the Dwyka group or leached from the granitic and metamorphic fragments contained within the Dwyka tillites. These inverse modelling results are supported by the saturation indices (SI) for calcite and dolomite in these springs which range from 0.74 to 0.82 and from 0.24 to 1.35, respectively indicating oversaturation with respect to these minerals and subsequent precipitation out of the aqueous solution. The precipitation of calcite, amorphous silica and iron carbonates were confirmed by the XRF, XRD and thin section results of the travertine rock samples. Acidic pH conditions (5.5), elevated TDS (5937 ppm), EC (3271 mS/m) and high trace metals concentration were detected in all CO² emission sites compared to CO² free streams, springs and boreholes. These results clearly show the impacts of CO² on groundwater and surface water quality within the vicinity of emission points. Therefore, it appears that natural CO² emission along the Bongwana fault have impacted the ambient groundwater and surface water quality at the emission sites rendering it unfit for human consumption due to elevated concentration of dissolved constituents above safe drinking standards. The implication of this to CCS in South Africa is the fact that any unintended CO² leakage into fresh groundwater and surface water resources from a failed subsurface storage facility may impact freshwater resources. Thus, strict scientific site selection protocols and properly designed monitoring systems are required to minimise the risk.
Hydrogeological and hydrochemical characterisation of the area around the Kusile Power Station, Mpumalanga.
(2022) Dlamini, Andile Eugene.; Demlie, Molla Bekele.
Abstract available in PDF.
Hydrogeological and hydrochemical investigation of the Durban Metropolitan District, Eastern South Africa.
(2018) Ndlovu, Minenhle Siphesihle.; Demlie, Molla Bekele.
Population and economic growth within the Durban Metropolitan region in eastern South Africa has increased the demand for water supply. This ever-increasing demand means that all available water supply sources including groundwater will be looked at, particularly in urban and peri-urban areas. However, the state of the groundwater resource in the region is poorly understood. This study aims to contribute towards improved understanding of the state of groundwater resources in the Metropolitan District through an integrated hydrogeological, hydrochemical and environmental isotope investigations. Results of hydrogeological and hydrogeochemical characterization identified at least five hydrostratigraphic units of varying hydraulic and hydrochemical characteristics. 1) The weathered and fractured Granitic basement aquifers of the Mapumulo Group and Oribi Gorge Suite characterized by average borehole yield and transmissivity (T) of 1.2 l/s and 3.9 m2/day, respectively, with hydrochemical facies of Ca-Mg-HCO3. 2) The fractured Natal Group sandstone, characterized by average borehole yield and hydraulic conductivity (K) of 5.6 l/s and 2.8 m/day, respectively with Na-Mg-HCO3-Cl as dominant water type; 3) The fractured aquifers of the Dwyka Group diamictite and tillite are characterized by average borehole yield of 0.4 l/s and T of 1.3 m2/day and Na-Cl-HCO3 as the dominant water type; 4) The Vryheid Formation, which is part of the Ecca Group, is characterized by a mean borehole yield of 2.5 l/s, T of 4.9 m2/day, K of 0.17 m/day and Na-Cl-HCO3 water type; 5) The intergranular primary aquifers of the Maputaland Group which consists the Bluff, Berea Formations and recent alluvium and estuarine deposits (locally called harbour beds Formation) have average borehole yield of 14.8 l/s and transmissivity of up to 406 m2/day with a mainly Na-Cl-HCO3 hydrochemical signature. The region receives mean annual precipitation (MAP) of 935 mm/yr of which 9.2% infiltrates to recharge the various aquifers. Environmental isotope information (2H, 18O and 3H) indicated that groundwater recharge is of modern precipitation. Groundwater tritium values of 37.4 and 92 TU are measured around the Bul Bul Drive and Bisasar Road Landfill sites, respectively, indicating groundwater contamination from landfill leachate leakage. Based on the main hydrogeological, hydrogeochemical and environmental isotope findings, a regional hydrogeological conceptual model is developed that characterizes the hydrogeological and hydrochemical conditions of the Durban Metropolitan region.
Hydrogeological conceptual modeling of the Kosi Bay Lakes system, north eastern South Africa.
(2015) Ndlovu, Mbali.; Demlie, Molla Bekele.
This M.Sc. Thesis focuses on the hydrogeological study of the Kosi Bay Lakes system, located in the north-eastern KwaZulu-Natal (KZN) Province of South Africa. The research catchment covers an area of about 659 km². It is characterised by four interconnected lakes, two isolated lakes and an estuary with a combined area of about 48 km². Two fresh water streams; namely, Sihadhla and Gezisa drain into the lakes. The study was initiated due to information gaps and the importance of the area with respect to conservation, ecology and water resources. The main objectives of the research was to characterize the groundwater and surface systems, in terms of their interconnection, flow and hydrochemistry; conduct a water balance study and develop a conceptual hydrogeological model on the occurrence and interaction of groundwater and surface water within the study area. The study has been undertaken by collecting primary data through a series of field campaigns in April 2013, May 2013 (onsite measurements and water, and water sampling) and October to December 2014 (geophysical data collection and supervision of borehole drilling). Original data generated in this study was complimented with data from KZN Groundwater Resource Information Project (GRIP), the National Groundwater Archives (NGA) and geophysical data, borehole logs, chemistry, and borehole yield data from consultant reports. Geophysical sounding data were calibrated using borehole logs and aquifer pumping tests, which indicate the presence of three hydrostratigraphic units in the study area, namely; the unconfined Holocene cover sands, the Kosi Bay and Port Durnford Formations, and the leaky-confined aquifer made up of the Umkhwelane and Uloa Formations, from top to bottom, respectively. The mean annual precipitation (MAP) for the study area based on data collected at Ingwavuma Kosi Bay and Ingwavuma Manguzi meteorological stations is 939 mm/year. The mean annual groundwater recharge estimated using the chloride mass balance method is 13% of the MAP. Surface water runoff from the catchment to the lakes derived using the Runoff Curve Number method is 14% of the MAP. Evaporation rate from the lakes and evapotranspiration from the catchment area estimated using the Penman and FAO Penman-Monteith approach are 1341 mm/a and 1135 mm/a, respectively. The water balance parameters indicate that inputs into the lakes are greater than the output as indicated by the positive change in storage (ΔS). The lake water balance result was supported by long-term lake level records that show an increasing trend over time. The measured electrical conductivity (EC) for the Kosi Bay Lakes range from 1024 μS/cm (Amanzamnyama) to 24600 (Makhawulani) μS/cm, for the groundwater from 86 to 400 μS/cm and for the streams, it ranges from 227 to 341 μS/cm. The high EC and TDS values of some of the Kosi Bay Lakes are attributed to the high evaporation and connection to the sea through the estuary. The shallow aquifers are characterized by Na-HCO₃-Cl, whereas the deep aquifers have a Na-Ca-Cl hydrochemical facies. All groundwater, stream and lake water samples have δ¹⁸O and δ²H values that plot on the local and global meteoric water lines indicating recharge from meteoric sources. Groundwater in the shallow Holocene aquifer and streams has similar hydrochemical and isotopic signature, indicating strong interconnection. On the other hand, the lakes are characterized by Na-Cl hydrochemical water type and an enriched stable isotopic signal (positive δD and δ¹⁸O signals) indicating evaporation and terminations of the local surface and groundwater flow system. The detectable tritium signal along with the low salinity of groundwater in the shallow aquifer reflect recent (< 50 years) recharge.
Investigating potential aquifers for managed aquifer recharge using treated wastewater around the greater Ethekwini District Municipality.
(2022) Msweli, Hlengiwe Fortunate.; Demlie, Molla Bekele.
Abstract available in PDF.

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Browsing Masters Degrees (Geology) by Author "Demlie, Molla Bekele."