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Over the past century, the world's rivers have become increasingly impounded to combat water scarcity and fossil-fuel reliance. Large dams have faded from popularity due to their adverse environmental effects, but small ponds and reservoirs continue to be constructed at high rates. Due to limited data regarding their size and flow, it has been difficult to assess how these smaller impoundments impact rivers. This study combined rainfall runoff data from the Chesapeake Bay Model with the unique routing framework of VA Hydro to create a simplistic hydrologic model capable of analyzing impoundment-induced flow alteration. Using standard design techniques and satellite imagery, a methodology was developed to build realistic stage-storage-discharge relationships for small and large impoundments. Eleven impoundments of the Difficult Run watershed were modeled within VA Hydro to assess their cumulative impact on downstream flow. Multiple models were created with different active impoundments and run for the full model period, 1984 - 2005. Flow alteration increased significantly with additional impoundments. Peak flows were attenuated as water was stored behind outlets, but median flows were increased as this water was slowly released. Average storm duration increased due to extended rising and falling limbs caused by impoundment outlets. Headwater channels increasingly ran dry, decreasing extreme low flows due to impoundment evaporation. Large reservoirs had a greater impact on median flows, but smaller ponds dominated low flow alteration. These results suggest that traditional hydrologic assumptions and metrics may be incapable of analyzing a changing flow regime without explicitly considering small and large impoundments upstream. / Master of Science / At first look, dams are an excellent solution to water scarcity and energy independence. They trap clean water and direct it through turbines. Unfortunately, their installation and operation creates many negative environmental impacts by fundamentally altering downstream channels, leading to a loss of fish vitality and river function. Large dam construction has decreased in the US because of these effects, but small dams continue to be built at high rates due to growing agricultural and stormwater demands. Their impact on rivers is less understood due to limited data availability regarding their size and function. This experiment used standard design techniques and widely available satellite data to create a representative model for dams of all size. Multiple tests were run, progressively increasing the number of dams within a watershed and analyzing their impact on downstream flow. With increased impoundment, high floods decreased in magnitude. However, more-typical medium flows increased. River flow became more static, with less extreme floods and more medium flows. The modeled dams greatly decreased drought flows as trapped water evaporated and decreased outflow. This impact was particularly noticeable in ponds that drained only a small area as they took longer to refill after drying. Larger dams more greatly impacted medium flows. These results contribute significantly to water availability prediction by more realistically representing dam processes. Although more work is needed to refine the impoundment modeling strategy, this study has effectively demonstrated that small and large dams affect flow in different manners and need to be accounted for accordingly.

Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal. / La question du pourquoi et du comment l’eau a disparue du paysage urbain est explorée dans cette étude des réservoirs à ciel ouvert du système d’approvisionnement en eau potable de la ville de Montréal. Une étude de cas de trois réservoirs, le McTavish (à ciel ouvert de 1856 à 1948), Côte-des-Neiges (de 1893 à 1938) et Vincent d’Indy (de 1915 à 1964), considère comment la forme et la fonction des réservoirs ont changé, alors qu’évoluaient les rapports entre facteurs environnementaux, moyens technologiques et préoccupations sociales dans la ville en croissance. Répondant aux avantages et défis de la topographie urbaine, ces réservoirs ont été construits sur les flancs du mont Royal. Le potentiel offert par ces réservoirs d’élargir le noyau de conservation de la montagne est exploré dans une reconsidération de leur situation dans la ceinture de sites institutionnels qui circonscrivent le coeur de ce principal paysage naturel et culturel de la ville. Un virage dans les développements de l’aqueduc, passant des questions quantitatives à des questions qualitatives, relié à la montée des perspectives de la santé publique et de l’environnement, était à l’origine du mouvement de couvrir les réservoirs. Toutefois, le coût élevé de la reconstruction des basins en boîtes de béton armé recouvert de pelouse et l’absence de règlements exigeant des toits sur les réservoirs, ont mené à des délais de plusieurs décennies. Par ailleurs, dans la ville en pleine expansion, l’augmentation de la capacité de stockage d’eau demeurait au moins aussi importante que la garantie de la qualité de l’eau. L’éthique d’efficacité qui en résulta est traduite dans les paysages des réservoirs transformés, pour lesquels les fonds et l’aménagement furent négligeables. Des conséquences imprévues mais cruciales de cette transformation sont examinées : la dissociation de l’approvisionnement d’eau de l’écosystème urbain; la perte de visibilité de l’aqueduc; la reconnaissance réduite de sa valeur collective; la responsabilité ambiguë de ces espaces ouverts et, comme conséquence, un manque d’entretien; la dissimulation de l’aqueduc et d’autres fonctions techniques dans le paysage de la montagne et le manque d’intégration des réservoirs dans les plans de conservation de la montagne. / The questions of how and why water has disappeared in the urban landscape are explored in this study of the uncovered reservoirs of the Montreal water supply system that were destined to be covered. A case study of three reservoirs, the McTavish (open from 1856 to 1948), the Côte-des-Neiges (from 1893 to 1938), and the Vincent d’Indy (from 1915 to 1964), considers how the form and function of these reservoirs changed, as the relationship between environmental factors, technological means and social concerns evolved in the developing city. In response to advantages and challenges of the city’s topography, the reservoirs were built on the flanks of Mount Royal. The potential the reservoirs offer to expand the mountain’s conservation core is explored in a reconsideration of their situation within a belt of institutional properties that delimit the heart of this principal natural and cultural landscape of the city. A shift in the focus of water supply development from quantitative to qualitative concerns, related to the rise of both public health and environmental perspectives, was a principal incentive to covering water supply reservoirs. Nevertheless, the expense of rebuilding the basins as reinforced concrete boxes covered in earth and sod, and the lack of regulations requiring covers on all reservoirs, lead to the process being delayed for decades. Furthermore, the city was in full expansion throughout this period, so that the pressure to increase the capacity of water storage rivalled that of guaranteeing water quality. The resulting focus on efficiency is embodied in the landscapes of the transformed reservoirs, in which little funds or planning resources were invested. Certain unplanned but critical consequences of this transformation are examined: the disassociation of water supply from the urban ecosystem; the loss of visibility of the waterworks; the decreased recognition of their collective value; the confusion about responsibility for these open spaces and a related lack of upkeep; the concealment of water supply and other technological functions in the mountain landscape; and the lack of integration of the reservoir sites in plans for the mountain’s conservation.

The purpose of this thesis is to determine the effect of hexadecanol on the populations of Pseudomonas and Alcaligenes species in reservoirs and determine their ability to utilize this compound as a carbon source.

The Karoo Basin of South Africa holds an estimated 906 billion to 11 trillion cubic meters of unconventional shale gas within the shales of the Whitehill and Collingham formations of the Ecca Group. Evaluation of this potential resource has been limited due to the lack of exploration and a scarcity of existing drill core data. In order to circumnavigate this problem this study was undertaken to evaluate the potential target horizons exposed in outcrops along the southern portion of the Karoo Basin, north of Grahamstown in the Eastern Cape Province. Detailed field logging was done on the exposed Whitehill and Collingham formations as well as a possible conventional sandstone (turbidite) reservoir, the Ripon Formation, along road cuttings of the Ecca Pass. Palaeocurrent data, jointing directions and fossil material were also documented. Samples were analysed for mineralogy, porosity, permeability, and total organic carbon content (TOC). The extensively weathered black shales of the Whitehill Formation contain a maximum TOC value of 0.9% and the Collingham Formation shales contain a maximum TOC value of 0.6%. The organic lithic arkose sandstones of the Ripon Formation are classified as ‘tight rock’ with an average porosity of 1% and an average permeability of 0.05 mD. The Whitehill Formation in the southern portion of the Karoo Basin has experienced organic matter loss due to low grade metamorphism as well as burial to extreme depths, thus reducing shale gas potential. The Ripon Formation is an unsuitable conventional reservoir along the southern basin boundary due to extensive cementation and filling of pore spaces.

Geothermal energy is the energy naturally present inside the earth crust. When a large volume of hot water and steam is trapped in subsurface porous and permeable rock structure and a convective circulating current is set up, it forms a geothermal reservoir. A geothermal system can be defined as - convective water in the upper crust of earth, which transfers heat from a heat source (in the reservoir) to a heat sink, usually the free surface. A geothermal system is made up of three main elements: a heat source, a reservoir and a fluid, which is the carrier that transfers the heat. As an alternative source of energy geothermal energy has been under attention of the researchers for quite some time. The reason behind this is the existence of several benefits like clean and renewable source of energy which has considerable environmental advantage, with no chemical pollutants or wastes are generated due to geothermal emissions, and the reliability of the power resource. Hence research has been directed in several directions like exploration of geothermal resources, modeling the characteristics of different types of geothermal reservoirs and technologies to extract energy from them. The target of these models has been the prediction of the production of the hot water and steam and thus the estimation of the electricity generating potential of a geothermal reservoir in future years. In a geothermal power plant reinjection of the heat depleted water extracted from the geothermal reservoir has been a common practice for quite some time. This started for safe wastewater disposal and later on the technology was employed to obtain higher efficiency of heat and energy extraction. In most of the cases a very small fraction of the thermal energy present in the reservoir can be recovered without the reinjection of geothermal fluid. Also maintaining the reservoir pressure is essential which gradually reduces due to continuous extraction of reservoir fluid without reinjection, especially for reservoirs with low permeabilities. Although reinjection of cold-water has several benefits, the possibility of premature breakthrough of the cold-water front, from injection well zone to production well zone, reduces the efficiency of the reservoir operation drastically. Hence for maintaining the reservoir efficiency and longer life of the reservoir, the injectionproduction well scheme is to be properly designed and injection and extraction rates are to be properly fixed. Modeling of flow and heat transport in a geothermal reservoir due to reinjection of coldwater has been attempted by several researchers analytically, numerically and experimentally. The analytical models which exist in this field deal mostly with a single injection well model injecting cold-water into a confined homogeneous porous-fractured geothermal reservoir. Often the thermal conductivity is neglected in the analytical study considering it to be negligible which is not always so, as proved in this study. Moreover heterogeneity in the reservoir is also a major factor which has not been considered in any such analytical study. In the field of numerical modeling there also exists a need of a general coupled three-dimensional thermo-hydrogeological model including all the modes of heat transport (advection and conduction), the heat loss to the confining rocks, the regional groundwater flow and the geothermal gradient. No study existing so far reported such a numerical model including those mentioned above. The present study is concerned about modeling the non-isothermal flow and heat transport in a geothermal reservoir due to reinjection of heat depleted water into a geothermal reservoir. Analytical and numerical models are developed here for the transient temperature distributions and advancement of the thermal front in a geothermal reservoir which is generated due to the cold-water injection. First homogeneous geothermal aquifers are considered and later heterogeneities of different kinds are brought into picture. Threedimensional numerical models are developed using a software code DuMux which solves flow and heat transport problems in porous media and can handle both single and multiphase flows. The results derived by the numerical models have been validated using the results from the analytical models derived in this study. Chapter 1 of the thesis gives a brief introduction about different types of geothermal reservoirs, followed by discussion on the governing differential equations, the conceptual model of a geothermal reservoir system, the efficiency of geothermal reservoirs, the modeling and simulation concepts (models construction, boundary conditions, model calibration etc.). Some problems related with geothermal reservoirs and geothermal power is also discussed. The scenario of India in the context having a huge geothermal power potential is described and different potential geothermal sites have been pointed out. In Chapter 2, the concept of reinjection of the heat depleted (cold) water into the geothermal reservoir is introduced. Starting with a brief history of the geothermal reinjection, the chapter describes the purpose and the need of reinjection of geothermal fluid giving examples of different geothermal fields over the world where reinjection has been in practice and benefitted by that. The chapter further discusses on the problems and obstacles faced by the geothermal projects resulting from the geothermal reinjection, most important of which is the thermal-breakthrough and cooling of production wells. Lastly the problem of this thesis is discussed which is to model the transient temperature distribution and the movement of the cold-water thermal front generated due to the reinjection. The need of this modeling is elaborated which represents the motivation of taking up the problem of the thesis. Chapter 3 describes an analytical model developed for the transient temperature in a porous geothermal reservoir due to injection of cold-water. The reservoir is composed of a confined aquifer, sandwiched between rocks of different thermo-geological properties. The heat transport processes considered are advection, longitudinal conduction in the geothermal aquifer, and the conductive heat transfer to the underlying and overlying rocks of different geological properties. The one-dimensional heat transfer equation has been solved using the Laplace transform with the assumption of constant density and thermal properties of both rock and fluid. Two simple solutions are derived afterwards, first neglecting the longitudinal conductive heat transport and then heat transport to confining rocks. The analytical solutions represent the transient temperature distribution in the geothermal aquifer and the confining rocks and model the movement of the cold-water thermal front in them. The results show that the heat transport to the confining rocks plays an influential role in the transient heat transport here. The influence of some parameters, e.g. the volumetric injection rate, the longitudinal thermal conductivity and the porosity of the porous media, on the transient heat transport phenomenon is judged by observing the variation of the transient temperature distribution with different values of the parameters. The effects of injection rate and thermal conductivity have been found to be high on the results. Chapter 4 represents another analytical model for transient temperature distribution in a heterogeneous geothermal reservoir underlain and overlain by impermeable rocks due to injection of cold-water. The heterogeneity of the porous medium is expressed by the spatial variation of the flow velocity and the longitudinal effective thermal conductivity of the medium. Simpler solutions are also derived afterwards first neglecting the longitudinal conduction, then the heat loss to the confining rocks depending on the situation where the contribution of them to the transient heat transport phenomenon in the porous media is negligible. Solution for a homogeneous aquifer with constant values of the rock and fluid parameters is also derived with an aim to compare the results with that of the heterogeneous one. The effect of heat loss to the confining rocks in this case is also determined and the influence of some of the parameters involved, on the transient heat transport phenomenon is assessed by observing the variation of the results with different magnitudes of those parameters. Results show that the heterogeneity plays a major role in controlling the cold-water thermal front movement. The transient temperature distribution in the geothermal reservoir depends on the type of heterogeneity. The heat loss to the confining rocks of the geothermal aquifer also has influence on the heat transport phenomenon. In Chapter 5 another analytical model is derived for a heterogeneous reservoir where the heterogeneous geothermal aquifer considered is a confined aquifer consisted of homogeneous layers of finite length and overlain and underlain by impermeable rock media. All the different layers in the aquifer and the overlying and underlying rocks are of different thermo-hydrogeological properties. Results show that the advancement of the cold-water thermal front is highly influenced by the layered heterogeneity of the aquifer. As the cold-water thermal front encounters layers of different thermo-hydrogeological properties the movement of it changes accordingly. The analytical solution derived here has been compared with a numerical model developed by the multiphysics software code COMSOL which shows excellent agreement with each other. Lastly it is shown that approximation of the properties of a geothermal aquifer by taking mean of the properties of all the layers present will lead to erroneous estimation of the temperature distribution. Chapter 6 represents a coupled three-dimensional thermo-hydrogeological numerical model for transient temperature distribution in a confined porous geothermal aquifer due to cold-water injection. This 3D numerical model is developed for solving more practical problems which eliminate the assumptions taken into account in analytical models. The numerical modeling is performed using a software code DuMux as mentioned before. Besides modeling the three-dimensional transient temperature distribution in the model domain, the chapter investigates the regional groundwater flow has been found to be a very important parameter to consider. The movement of the thermal front accelerates or decelerates depending on the direction of the flow. Influence of a few parameters involved in the study on the transient heat transport phenomenon in the geothermal reservoir domain, namely the injection rate, the permeability of the confining rocks and the thermal conductivity of the geothermal aquifer is also evaluated in this chapter. The models have been validated using analytical solutions derived in this thesis. The results are in very good agreement with each other. In Chapter 7 the main conclusions drawn from the study have been enlisted and the scope of further research is also pointed out.

[pt] Tradicionalmente, os testes de formação em poços de petróleo buscam caracterizar o campo de permeabilidades a partir da interpretação dos transientes de pressão (PTA) nos períodos de fluxo e estática baseados em modelos isotérmicos de escoamento em meios porosos. Com o avanço da instrumentação dos testes, registros mais precisos de temperatura passaram a estar disponíveis e fomentaram a pesquisa baseada em modelos não isotérmicos que possibilitaram a análise a partir dos transientes de temperatura (TTA). Além da caracterização de parâmetros do reservatório como permeabilidade e porosidade com a interpretação dos transientes de temperatura, os dados de pressão obtidos a partir de um modelo não isotérmico representa de forma mais fidedigna o fenômeno físico sobretudo quando os testes são submetidos a maiores diferenciais de pressão. Este trabalho consiste no desenvolvimento de um simulador para teste de formação que considera a modelagem não isotérmica de reservatório unidimensional radial acoplado a um poço produtor e na utilização deste simulador, associado a métodos de otimização multivariável, para resolução do problema inverso da caracterização de parâmetros do reservatório. Alguns métodos de otimização foram testados e o algoritmo do Simplex de Nelder-Mead apresentou melhor eficácia. Foram estabelecidos três tipos de problemas e utilizados em três casos hipotéticos considerando inclusive a imposição artificial de ruídos nos sinais de pressão e temperatura utilizados para resolução do problema inverso. / [en] Traditionally, oil well formation tests aim to characterize the reservoir permeability field from pressure transient analysis (PTA) of drawdown and build up based on isothermal flow models in porous media. With the advancement of well test instrumentation, more accurate temperature records became available and have encouraged researches based on non-isothermal models that made possible the temperature transient analysis (TTA). In addition to the characterization of reservoir parameters such as permeability and porosity by TTA, the pressure data obtained from a non-isothermal model represent better the physical phenomenon, especially when the tests are subjected to greater drawdowns. This work consists in the development of a simulator for formation test that considers non-isothermal modeling of a unidimensional radial reservoir coupled to a production well and in the use of this simulator, associated with multivariable optimization methods, to solve the inverse problem of reservoir parameters characterization. Some optimization methods were tested and the Nelder-Mead Simplex algorithm presented better efficiency. Three types of problems were established and used in three hypothetical cases, including artificially imposed noise in pressure and temperature signals used to solve the inverse problem.

Increasing demands regarding performance, safety and environmental compatibility of hydraulic mobile machines in combination with rising cost pressures create a growing need for specialized optimization of hydraulic systems; particularly with regard to hydraulic reservoirs. In addition to the secondary function of cooling the oil, two main functions of the hydraulic reservoir are oil storage and de-aeration of the hydraulic oil. While designing hydraulic reservoirs regarding oil storage is quite simple, the design regarding de-aeration can be quite difficult. The author presents an approach to a system optimization of hydraulic reservoirs which combines experimental and numerical techniques to resolve some challenges facing hydraulic tank design. Specialized numerical tools are used in order to characterize the de-aeration performance of hydraulic tanks. Further the simulation of heat transfer is used to study the cooling function of hydraulic tank systems with particular attention to plastic tank solutions. To accompany the numerical tools, experimental test rigs have been built up to validate the simulation results and to provide additional insight into the design and optimization of hydraulic tanks which will be presented as well.

Thesis (PhD)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: Aquaculture has proven to be a viable operation in multi-used irrigation reservoirs (also referred to as farm dams) in the Western Cape province (WCP) of South Africa. Many studies found that the fitness-for-use of these reservoirs for both net cage culture of fish and irrigation of crops is feasible. However, practising intensive fish farming in existing open water bodies can increase the nutrient levels of the water through organic loading, originating from uneaten feeds and fish metabolic wastes. Under such conditions the primary (irrigation) and secondary (drinking water and recreation) usage of the dam could be compromised by deteriorating water quality. Rainbow trout (Oncorhynchus mykiss) farming is done in Mediterranean climatic conditions of the WCP. This type of climate presents short production seasons with fluctuating water quality and quantity. The study investigated the dynamics of water physico-chemical parameters and assessed the long term impact of rainbow trout farming on irrigation reservoirs. Furthermore, associated land-use in the catchment of such integrated aqua-agriculture systems is described, and mitigation to minimise the impact of fish farming evaluated. The investigation concluded with assessing the contribution of aquaculture to rural and peri-urban communities. The aim is to present an integrated, socio-ecologically balanced farming system for irrigation reservoirs with associated aquaculture activities. A total of 35 reservoirs, including both fish farming and non-fish farming ones, were selected as research sites. They were located in three geographical regions namely, Overberg (Grabouw/Caledon), Boland (Stellenbosch/Franschhoek) and Breede River (Ceres/Worcester). Reservoirs were <20 ha in surface area and the volume ranges from 300 000 to 1 500 000 m3. Water samples were collected monthly and seasonally for the different investigations and analysed for a range of water quality parameters, including: transparency (Secchi disc), temperature, dissolved oxygen (DO), pH, sodium (Na), potassium (K), calcium (Ca), magnesium (Mg), iron (Fe), chloride (Cl), carbonate (CO3), bicarbonate (HCO3), manganese (Mn), copper (Cu), zinc (Zn), boron (B), total phosphorous (TP), orthophosphate (PO4), total ammonia nitrogen (TAN), nitrate-nitrogen (NO3-N), nitrite-nitrogen (NO2-N), aluminium (Al), total suspended solids (TSS), total dissolved solids (TDS), alkalinity, hardness and sulphate. Phytoplankton samples were also collected, genera identified and biomass calculated. The water quality data were analysed in terms of surface and bottom strata in both fish farming and non-fish farming reservoirs based on repeated measurements at the same site location at different times using the procedure General Linear Models of Stastical Analysis System (SAS, 2012). Values p<0.05 were considered as statistically significant. A Principal Component Analysis (PCA) biplot was used to graphically depict all the sites and measured water quality variables with the purpose of trying to see whether the fish farming and non-fish farming ones showed any groupings and how the sites were related to the measured variables. Structured questionnaires and informal discussions were used to collect additional information on the water use, production data and socio-economic effects on fish farmers. Categorical data gathered from the interviews (21 aquaculture projects) were analysed for frequency of occurrence using the Statistical Product and Service Solutions (SPSS) computer programme (SPSS Systems for Windows, Version 12.0). Results are presented in publication form with research chapters focusing on the subject areas of water quality impact, catchment land-use, potential mitigation measures and aquaculture contribution. Results for the water quality analyses indicated that as a collective, the farm reservoirs’ overall minimum, mean and maximum values for the physico-chemical parameters were fit-for-use for trout farming. The depth of the reservoirs ranged from 1.2 - 21.6 m with the low value taken during the summer season. Values lower than 5.0 m can cause management problems for floating cages that require a minimum of 4.0 m for net suspension and 1.0 m of free space below for adequate lateral flow. The Secchi disc reading of the reservoirs ranged from 10 – 510 cm. Higher transparencies were recorded after the winter rains when sand, silt and clay settled. Trout feeding is dependent on visibility and transparencies of more than 50 cm are required for good feeding conditions. The dissolved oxygen (DO) ranged from 0.3 – 16.4 mg/L with values below 5.00 mg/L recorded during summer when extraction and temperatures were high and provided conditions unable to sustain trout farming. The situation reverses with the onset of winter when the dams fill and DO rises above 5.00 mg/L as required for trout farming. The phosphorous (P) levels ranged from 0.001 – 0.735 mg/L. Higher concentrations were recorded during the winter turnover phase when bottom and surface waters mixed. Concentration above 0.01 mg/L can cause eutrophication of the water bodies. Total ammonia nitrogen (TAN) ranged from 0.015 - 6.480 mg/L. Higher concentrations were recorded during summer when temperatures were high and depths were low. TAN can be toxic to fish when the pH and temperature are high. The generally low least square means (LSM) for TAN were indicative of minor environmental impact of trout farming operations conducted during the colder, winter rainfall months. Trout farming coincided with conditions where the water temperatures were low, dam levels were high and dams were overflowing. The difference in bottom and surface water quality of reservoirs and the site location were found to be more important than the absence or presence of fish farming. The difference in bottom and surface water is directly linked to the ecological status of the sediment, which serve as nutrient sinks. In monomictic dams found in Mediterranean areas, mixing occurs during the winter turnover phase. Nutrients are released due to surface and bottom water mixing, brought about by torrential rains and wind turbulence. The concentration of organic material in the sediment and bottom waters is a function of the nutrient loading over time, irrespective whether the non-point sources were fish farming or agricultural activities and therefore it is difficult to partition causes and effects. In cases where reservoirs were already eutrophic due to past agricultural practices, implementing aquaculture could exacerbate the poor water quality status of the reservoir. There was a statistically significant difference between fish farming and non-fish farming for phosphorous, Secchi disc, total suspended solids and nitrite-nitrogen (p<0.05) and no statistically significant difference between fish farming and non-fish farming for dissolved oxygen, total ammonia nitrogen and nitrate-nitrogen (p>0.05). There was a statistically significant difference between surface and bottom waters for P and TAN (p<0.05). One reason for higher P and TAN concentrations in bottom waters is the accumulation of both in the sediment and subsequent release in the water column when the water mixes. A two-dimensional scatter plot was generated using the score for the first two principal components. The first two principal components accounts for 40 and 17 % of the total variance respectively, and the two groups of fish farming and non-fish farming did not separate well based on the first two principal components. The occurrence and distribution of phytoplankton biomass fluctuated with dam water levels and nutrient concentrations. The prevailing phytoplankton communities are important to fish farmers for two reasons: 1. It leads to fluctuations in dissolved oxygen concentrations via users (respiration and decomposition) and producers (photosynthesis). 2. It could lead to algal taint of fish flesh when geosmin-producing phytoplankton species are present. The frequency of occurrence indicated that the Group Chlorophyta (including genera, Chlamydomonas, Closterium, Oocystis, Scenedesmus, Staurastrum, Tetraedron, etc) had the most occurrences (n=371) with Chrysophyta (including genera, Dinobryon, Mallomonas, Synura, etc) the least (n=34). There was a statistically significant difference between genera occurrence and season (p<0.05). The geographical location of sites had no significance influence on the frequency of phytoplankton occurrence. There was no direct link between water quality and production yield (p>0.05). The fish yield of farms were linked mainly to the quality of fingerlings and the feed conversion ratio (FCR) achieved (p<0.05). Land-use patterns in the catchment where fish farming dams were located have shown that the dams are multiple-used systems. The ecological integrity of the farm dam ecosystem is dependent on the base volume. The dam is primarily for irrigation and fish farming can be compromised when higher demand for water is required during the dry season. The dams receive about 20 % of its water from rainfall and the rest from runoffs. Farmers could not provide accurate extraction rates making it difficult to predict water levels for future fish production. Four potential mitigation measures to reduce nutrient loading were described namely, feed management (quantity, frequency, type, etc.), feeding method (demand feeders, hand feeding), feed ingredients (formulation) and floating gardens. Both feed management procedures and demand feeders were evaluated as to the efficiency of reducing feed wastage and optimising FCR’s. The small-scale fish farmers were producing approximately 6 tons and had an average FCR of 1.96:1 ± 1.15. If farmers could improve their FCR’s by 0.1 (i.e. from 1.96 to 1.86), it would translate into a reduction of 100 kg feed for every ton of fish produced and result in 5% decrease in nutrient loading. The results of the water analysis and visual assessment of faecal length and colour showed no statistically significant difference between treatments for the guar-gum based binder (p>0.05). In addition, the level of binder did not influence digestibility of the experimental diets. The floating garden study indicated that it was feasible to construct a low cost raft system that is easy to manage and can produce plant crops as a hydroponic system in conjunction with fish farming cages. The lettuces grown on farm dam water provided support for the premise that the water quality can be improved via extraction of nutrients for crop production. For the production of 3.5 kg/m2 lettuce, a ratio of 1.09 plants/fish equal to 1.84 g feed/day/plant would reduce the accumulation of soluble nutrients around floating net cage farming system. The socio-economic evaluation of the contribution of fish farming to the welfare of rural and peri-urban farming communities supported the notion that aquaculture can lead to the upliftment of participating communities. Seventy-one percent (71%) of the respondents indicated that their motivation for exploring aquaculture is to supply fish to the wholesale market in order to generate income. Sixty-one percent (61%) of the respondents conducted the sales themselves or co-opted family members to assist them. The contribution of aquaculture provided direct benefits through improvement in household income, subsistence food supply and skills development. Indirect benefits included providing an information hub for other emerging farmers, elevation of the fish farmer’s status in the community through greater wealth and knowledge creation and promoting sector diversification through new products and technology. The three main constraints to the promotion and growth of aquaculture were listed as lack of government support, insufficient market intelligence and access, and limited choice in the availability of suitable candidate aquaculture species. Irrigation reservoirs in the WCP have a history of enrichment through external sources supplying water via agricultural runoff (fertilisers and pesticides), catchment runoff (leaf litter and organic debris) and stormwater effluent (grey and black water). The incorporation of aquaculture into such dams adds extra nutrients to the water column and management is crucial to limit the nutrient loading and ensure environmental sustainability. Such an approach will ensure that commercial land-based crop farmers’ irrigation regime and water distribution operations would not be negatively affected. Therefore future research needs should focus on; firstly the prevention and minimisation of pollution deriving from aquaculture through improved production management and technology transfer, secondly the monitoring and evaluation of the catchment ecosystem as a continuum with all the external factors affecting the ecology of farm dams and thirdly, evaluating the sediment processes and dynamics as sinks for nutrient accumulation. / AFRIKAANSE OPSOMMING: Akwakultuur het getoon dat dit ‘n lewensvatbare inisiatief is vir meerdoelige-gebruik van besproeiingsdamme (ook genoem plaasdamme) in die Wes-Kaap provinsie (WKP) van Suid-Afrika. Vele studies het bewys dat die geskiktheid-vir-gebruik van die reservoirs haalbaar is vir beide visproduksie sowel as besproeiing van landbougewasse. Nieteenstaande, die beoefening van intensiewe visboerdery in bestaande buitelug watersisteme kan lei tot ‘n toename in nutriëntvlakke van die water as gevolg van organiese belading afkomstig van ongevrete voere en metaboliese afvalstowwe van die vis. Onder sulke omstandigthede kan die primêre- (besproeiing) en die sekondêre (drinkwater en rekreasie) gebruik van die dam in gedrang kom weens ‘n afname in waterkwaliteit. Reënboogforel (Oncorhynchus mykiss) boerdery word beoefen in die omliggende Mediterreense klimaat van die WKP. Die tipe klimaat verskaf kort produksie-seisoene met wisselvallige water kwaliteit en kwantiteit. Die studie het die dinamika van water se fisies-chemiese parameters ondersoek en het die impak van forelboerdery op besproeiingdamme oor die langtermyn beskryf. Verder het die studie die geassosieerde landgebruik in die opvangsgebied met geïntegreerde akwa-landbou sisteme beskryf, asook moontlike toetrede (mitigasie maatreëls) geëvalueer wat die impak moontlik kan verlaag. Die ondersoek is afgesluit deur die bydrae wat akwakultuur lewer aan landelike en semi-stedelike gebiede, te beskryf. Die hoofdoel is die daarstelling van ‘n geïntegreerde, sosio-ekologiese gebalanseerde sisteem vir besproeiingdamme met gesamentlike akwakultuuraktiwiteite. ‘n Totaal van 35 besproeiingsdamme, insluitend die met visboerdery en nie-visboerdery, is gekies as navorsingspersele. Dit is hoofsaaklik geleë in drie geografiese gebiede naamlik, Overberg (Grabouw/Caledon), Boland (Stellenbosch/Franschhoek) en Breederivier (Ceres/Worcester). Die reservoirs is almal < 20 ha in oppervlakarea en die volumes het gewissel van 300 000 – 1 500 000 m3. Watermonsters is maandeliks sowel as seisoenaal versamel vir die onderskeie ondersoeke en ontleed vir ‘n reeks van parameters, insluitend: sigbaarheid (Secchi disc), temperatuur, opgeloste suurstof (OS), pH, natrium (Na), kalium (K), kalsium (Ca), magnesium (Mg), yster (Fe), chloor (Cl), karbonaat (CO3), bikarbonaat (HCO3), mangaan (Mn), koper (Cu), sink (Zn), boor (B), totale fosfor (TP), ortofosfaat (PO4), totale ammoniak stikstof (TAN), nitraat-stikstof (NO3-N), nitriet-stikstof (NO2-N), aluminium (Al), totale gesuspendeerde vaste stowwe (TGV), totale opgeloste vaste stowwe (TOV), alkaliniteit, hardheid en sulfate. Phytoplanktonmonsters is ook versamel, genera geïdentifiseer en die biomassa bepaal. Die waterkwaliteitsdata is ontleed in terme van oppervlak- en bodemstrata vir beide visboerdery en nie-visboerdery reservoirs en was gebaseer op herhaalde metings by dieselfde perseel op verskillende tye deur gebruik te maak van die Algemene Liniêre Model van Statistiese Analitiese Sisteem (SAS, 2012). Waardes p<0.05 is oorweeg as statisties beduidend. ‘n Hoofkomponentanalise bi-stipping (HKA) is toegepas om die persele en veranderlikes grafies voor te stel en te bepaal of die visboerdery en nie-visboerdery s’n enige groeperinge vorm asook hoe die persele assosieer met die veranderlikes. Gestruktureerde vraelyste en informele besprekings is onderneem om inligting in te samel op watergebruik, produksie-data, en die sosio-ekonomiese invloed wat akwakultuur bied aan visboere. Kategoriese data wat deur die onderhoude (21 akwakultuurprojekte) ingesamel is, is ontleed vir die frekwensie van aanwesigheid deur die gebruik van Statistiese Produk en Dienste-oplossings (SPDO) rekenaarprogram (SPSS Systems for Windows, Version 12.0). Die resultate vir die verskeie ondersoeke is beskryf en saamgestel in publikasie-vorm met die navorsingshoofstukke wat gefokus het op die areas van waterkwaliteitsimpak, opvangsgebied landgebruik, toetrede-meganismes en die bydrae van akwakultuur. Die resultate vir die waterkwaliteitsanalises het getoon dat gesamentlik die reservoirs se oorhoofse minimum, gemiddelde en maksimum waardes vir die verskillende fisies-chemiese parameters geskik is vir forelboerdery. Die diepte van die reservoirs het gewissel van 1.2 - 21.6 m, met die laagste waarde aangeteken gedurende die somermaande. Waardes laer as 5.0 m kan bestuursprobleme vir drywende hokstelsels versoorsaak want ‘n minimum van tenminste 4.0 m vrye spasie onder die hokke word benodig vir voldoende laterale vloei. Die Secchi-skyf lesing (sigbaarheid) van die reservoirs het gewissel van 10 – 510 cm. Hoër sigbaarheidswaardes is aangeteken na winterreëns wanneer sand-, slik- en klei deeltjies uitgesak het. Forel voer op sig en sigbaarheid van > 50 cm word benodig om goeie voeding te handhaaf. Die OS het gewissel van 0.3 – 16.4 mg/L met waardes onder 5 mg/L aangeteken gedurende somer wanneer wateronttrekking en temperature hoog was. Dit het gelei tot ongunstige toestande vir forelboerdery. Die situasie swaai om met die begin van winter wanneer die damme vol reën en die OS bo 5 mg/L styg soos benodig vir forelboerdery. Die P-vlakke het gewissel van 0.001 – 0.735 mg/L. Hoër waardes is aangeteken gedurende die winteromkeerfase wanneer die bodem en oppervlak se water meng. Konsentrasies bo 0.01 mg/L kan tot eutrofikasie van watersisteme lei. TAS het gewissel van 0-015 – 6.480 mg/L. Hoër konsentrasies is aangeteken gedurende die somer wanneer temperature hoog is en damvlakke laag. By hoë pH’s en temperature kan TAS toksies wees vir vis. The algemene lae kleinste kwadaat gemiddelde (KKG) waarde vir TAS het getoon dat daar ‘n klein impak op die omgewing was wanneer forelboerdery bedryf word gedurende die koue, winter reënvalmaande. Forelboerdery val saam met omstandigthede wanneer die watertemperature laag is, damvlakke hoog en die reservoirs oorloop. Die verskil in die bodem- en oppervlak water in die besproeiingsdamme en die ligging van die perseel is vasgestel om meer belangrik te wees as die teenwoordigheid of afwesigheid van visboerdery. Die verskil in die bodem en oppervlak is toe te skryf aan die toestand van die sediment waar nutriënte kan opgaar. In monomiktiese damme soos gevind in Mediterreende areas, vind vermenging plaas gedurende die winteromkeerfase. Nutriënte word vrygestel a.g.v. die vermenging van die oppervlak en bodem se water wat dan veroorsaak word deur harde reën en windturbulensie. Die konsentrasie van organiese materiaal in die sediment en bodem water is ‘n funksie van die nutriëntlading met tyd, ongeag of dit afkomstig was vanaf visboerdery of landbou-aktiwiteite. Dit is dus moelik om die spesifieke oorsaak van besoedeling af te baken. In gevalle waar die reservoirs alreeds eutrofies is a.g.v. aangewese landbouaktiwiteite, kan die toestand van die waterbron vererger indien akwakultuur toegepas word. Daar is ‘n statistiese noemenswaardige verskil tussen visboerdery en nie-visboerdery vir P, Secchi-skyf, totale gesuspendeerde vaste stowwe en nitrite-stikstof (p<0.05), en geen statistiese noemenswaardige verskil tussen visboerdery en nie-visboerdery vir OS, TAS en nitraat-stikstof (p>0.05). Daar is ‘n statistiese noemenswaardige verskil tussen oppervlak- en bodem water vir P en TAS (p<0.05). Een moontlike rede vir hoër P en TAS konsentrasies in die bodemwater, is die akkumulasie van beide parameters in die sediment en gevolglike vrystelling in die waterkolom wanneer die water gemeng word. ‘n Twee dimensionele spreidingstipping is geprodueer deur die waardes te gebruik van die eerste twee hoofkomponente. Die eerste twee hoofkomponente dra by 40 % en 17 % van die totale variansie onderskeidelik, en die twee groepering van visboerdery en nie-visboerdery het nie duidelik getoon nie. Die voorkoms en verspreiding van phytoplankton biomassa het gewissel met die verandering in damvlakke en nutriëntkonsentrasies. Die aanwesige phytoplanktongemeenskappe is belangrik vir die visboer vir twee redes: 1. Dit kan wisselende OS-vlakke versoorsaak deur die verbruik (respirasie en dekomposisie) en produksie (fotosintese) daarvan. 2. Dit kan lei tot alge na-smake van vis wanneer geosmin-produserende phytoplankton spesies aanwesig is. The frekwensie van voorkoms het getoon dat die Groep Chlorophyta (insluitend die genera, Chlamydomonas, Closterium, Oocystis, Scenedesmus, Staurastrum, Tetraedron, ens.) die meeste voorkom (n=371), met Chrysophyta (insluitend die genera, Dinobryon, Mallomonas, Synura, ens.) die minste (n=34). Daar is ‘n statistiese noemenswaardige verskil tussen genera voorkoms en seisoen (p<0.05) vir phytoplankton. Die geografiese ligging van die perseel het geen noemenswaardige invloed op die frekwensie van phytoplankton voorkoms nie. Daar is geen statistiese noemenswaardige verbintenis tussen waterkwaliteit en visproduksieopbrengste nie (p>0.05). Die visopbrengste by plase is hofsaaklik afhangende van die kwaliteit van die vingerlinge en die voeromsettingsverhouding (VOV) wat bereik is (p<0.05). Die landgebruikspatrone in die opvangsgebied waar visboere gesetel is, het aangedui dat die besproeiingsdamme meeldoelige sisteme is. Die ekologiese integriteit van die plaasdam-ekosisteem is afhanklik van die basisvolume. Die dam is hoofsaaklik daar vir die besproeiing en visboerdery kan in gedrang kom wanneer daar ‘n hoër aanvraag vir water gedurende die droë seisoen is. Die damme het omtrent 20 % van die water vanaf reënval ontvang en die res van aflope. Boere kon nie akkurate inligting verskaf van waterontrekking nie wat dit moeilik gemaak het om te voorspel wat die beskikbare watervlakke in die toekoms sou wees vir visproduksie. Vier potensiële toetrede meganismes om die nutriëntlading te verminder, is beskryf naamlik voedingsbestuur, (kwantiteit, frekwensie, tipe, ens.) voermetodes (aanvraagvoeder, handvoeding), voerbestandele (formulasies) en drywende tuine. Beide voedingsbestuur prosedure en aanvraagvoeders is geëvalueer as ‘n metode om die voervermorsing te verminder en die VOV te verbeter. Die kleinskaalse visboere het ongeveer 6 ton produseer met ‘n gemiddelde VOV van 1.96:1 ± 1.15. Indien die visboere hul VOV’s met 0.1 kan verbeter (bv. van 1.96 tot 1.86), sal dit beteken dat daar ‘n vermindering van 100 kg voer bewerkstellig word vir elke ton vis geproduseer. Dit kan ook lei tot ‘n vermindering van 5 % in die nutriëntlading. Die resultate van die wateranalises en die visuele waarneming van faeceslengte en kleur het geen statistiese noemenswaardige verskil tussen die behandelinge vir die guar-gom binder getoon nie (p>0.05). Verder, die hoeveelheid van die binder het nie die vertering van die eksperimentele diëte beïnvloed nie. Die studie op die drywende tuine het getoon dat dit haalbaar is om ‘n lae-koste sisteem te bou wat maklik is om te bestuur en gewasse kan produseer soos in ‘n hidroponiese sisteem tesame met visproduserende hokstelsels. Die kropslaaie se groei het getoon dat die waterkwaliteit van besproeiingsdamme kan verbeter word deur die opname van nutriënte wanneer plante verbou word. Vir die produksie van 3.5 kg/m2 kropslaaie, sal ‘n verhouding van 1.09 plante/vis of 1.84 g voer/dag/plant die akkumulasie van opgeloste nutriënte rondom die hokstelsels verminder. Die sosio-ekonomiese evaluasie van die bydrae van visboerdery tot die welvaart van die landelike en semistedelike plaasgemeenskappe ondersteun die feit dat akwakultuur verbetering kan bewerkstellig, veral onder deelnemende gemeenskappe. Een-en sewentig persent (71 %) van die respondente het getoon dat hul oorweging vir die bedryf van akwakultuur is om vis te voorsien aan die grootmark en daarvolgens geld te maak. Een-en-sestig persent (61 %) van die respondente het aangedui dat hulself die vis verkoop of vir familie-lede vra om met die verkope te help. Die bydrae van akwakultuur het direkte voordele aan die deelmers voorsien deur ‘n verbetering in huishoudelike inkomste, voedselvoorsiening vir selfgebruik en die ontwikkeling van vaardigthede. Indirekte voordele sluit in dat die deelmers ‘n bron van inligting geword het vir opkomende boere, hul status in die gemeenskap het verbeter omdat hul kennis verbreed het en dit het verder gelei tot diversifisering in die sektor a.g.v. die skepping van nuwe produkte en tegnologie. Die drie hoof struikelblokke wat die groei en bevordering van akwakultuur belemmer is o.a., ‘n tekort aan staatsondersteuning, onvoldoende markinligting en toegang en ‘n beperkte keuse in spesies vir boerdery. Besproeiingsdamme in die WKP het ‘n geskiedenis van verryking deur eksterne bronne wat water voorsien vanaf landbou-afloop (bemestingstowwe en pesbestrydingsmiddels), opvangsgebied-afloop (blare en ander organiese debris) en stormwateruitlaat (gruis- en swart water). Die implementering van akwakultuur in sulke damme voeg addisionele nutriënte tot die waterkolom en bestuur is krities om die lading te verminder en te verseker dat omgewingsvolhoubaarheid behou word. Indien die regte praktyke en bestuur toegepas word, sal dit beteken dat die kommersiële boer se besproeiing en waterverspreiding nie negatief beïnvloed word nie. Vervolgens moet toekomstige navosingsbehoeftes fokus op eerstens, die voorkoming en vemindering van besoedeling afkomstig van akwakultuur deur verbeterde produksie-bestuur en tegnologie-oordrag, tweedens, die monitoring en evaluering van die opvangs-ekosisteem as ‘n kontinuum met al die eksterne faktore wat die ekologie van die plaasdam kan beïnvloed en laastens, die ondersoek en evaluering van die sediment se prosesse en dinamika as ‘n sisteem wat nutriënte ophoop.

As easy target reservoirs are depleted around the world, the need for intelligent enhanced oil recovery (EOR) methods increases. The first part of this work is focused on modeling aspects of novel chemical EOR methods for naturally fractured reservoirs (NFR) involving wettability modification towards more water wet conditions. The wettability of preferentially oil wet carbonates can be modified to more water wet conditions using alkali and/or surfactant solutions. This helps the oil production by increasing the rate of spontaneous imbibition of water from fractures into the matrix. This novel method cannot be successfully implemented in the field unless all of the mechanisms involved in this process are fully understood. A wettability alteration model is developed and implemented in the chemical flooding simulator, UTCHEM. A combination of laboratory experimental results and modeling is then used to understand the mechanisms involved in this process and their relative importance. The second part of this work is focused on modeling surfactant/polymer floods using a fully implicit scheme. A fully implicit chemical flooding module with comprehensive oil/brine/surfactant phase behavior is developed and implemented in general purpose adaptive simulator, GPAS. GPAS is a fully implicit, parallel EOS compositional reservoir simulator developed at The University of Texas at Austin. The developed chemical flooding module is then validated against UTCHEM. / text