>Magister Scientiae - MSc / Over half of total flows in the global river network are composed of non-perennial rivers. This indicates the importance of non-perennial river systems in supporting the biodiversity. It has been established that groundwater is one of the elements that control the flow regimes and classification (whether perennial or not) of a river system. However, the use of hydrogeological characteristics to establish the influence of groundwater on non-perennial river systems remain to be widely unpublished. This study, therefore, intends to conceptualize and explain the role of hydrogeological characteristics in non-perennial rivers, using the Heuningnes catchment in the Western Cape Province of South Africa as a case study. The study has argued that thorough characterization of aquifers is essential in order to adequately establish the extent of aquifer-river connectivity and how groundwater influences flows and chemical loading in non-perennial river systems. The study has three objectives namely: (i) to determine the aquifer characteristics (ii) to characterise the aquifer-river interaction and (iii) to conceptualize the groundwater flow system. Records review, field, analytical and laboratory-based methods were used to collect and interpret geological, groundwater level, pumping test, hydro-chemical and environmental stable isotopic data in order to characterise groundwater occurrence, flow system and its interaction with the rivers of the study area. Water samples were taken from groundwater, surface water and rainfall during both dry and wet periods. Results show that the study area has a topography-controlled water table with shallow depth to groundwater levels ranging on average from 3 - 10 m, which result into largely a local groundwater flow system. Transmissivity values determined from constant rate pumping test range between 0.17 and 1.74 m2/day. Results exhibit that the low transmissivity values are associated with the weathered nature of the Table Mountain sandstone and the unfractured Bokkeveld shale formations. Hydrochemical data results indicate that both groundwater and river samples in the upstream part of the study area are characterised as fresh water with TDS values of less than 1000 mg/l while the downstream part has saline waters with TDS ranging from 2000 – 35000 mg/l. Results also show that Na-Cl is the dominant water composition for both groundwater and river water. The order of major ion dominance is similar for the two water sources, with concentration ranges from high to low in the order of Na+>Mg2+>Ca2+>K+ and Cl->SO42->HCO3- for cations and anions respectively. The similar patterns and trends in salinity and major ion data suggest the connectivity between the aquifer and the river. Environmental stable isotope data indicate river samples in upstream areas having depleted δ18O (-4.3 to -5.12‰) and δ2H (-22.9 to -19.3‰) signatures similar to groundwater indicating a stable and continuous groundwater contribution to the river flows. Meanwhile, high evaporative enrichment of δ18O (1.13 to 7.08‰) and δ2H (38.8 to 7.5‰) is conceived in river samples from downstream areas. Ionic ratios and isotope-salinity relationships suggest that groundwater chemistry is derived from sea sprays, evaporation and dissolution of Bokkeveld shale host rock. Geological, hydrogeological, hydrochemical and environmental stable isotope data were used to develop a conceptual hydrogeological model which explains the role of groundwater in non-perennial river systems. Results indicate that the North East – South West fault on the north-eastern part of the study area seem to act as a conduit to groundwater flow thereby supplying water to the upstream rivers while the East -West fault in the northern part seem to act as a barrier to groundwater flow resulting into a hydraulic discontinuity between upstream and downstream areas. Meanwhile, the relatively low conductive formation in the downstream areas coupled with a relatively low hydraulic gradient (0.000843) suggests there is slow Darcian groundwater flows resulting in less flushing and high salinization of groundwater. Eventually, in the downstream part of the study area there is slow and minimal groundwater discharge to the rivers resulting into groundwater failing to maintain the river flows and pools. In general, rivers of the study area largely gain water from groundwater although the amount of groundwater discharge varies from one river segment to another in both upstream and downstream parts. The conceptual model has led to the development of a proposed optimum management of non-perennial rivers including the effects of groundwater abstraction on the river flows. / 2022-09-01

Orientador: Paulo César Lodi / Resumo: Esse trabalho avaliou as propriedades do poliestireno expandido (EPS) para verificar a viabilidade e emprego deste em obras geotécnicas. Foram estudadas as propriedades mecânicas e hidráulicas do material, por meio de ensaios de resistência ao cisalhamento direto, compressão triaxial, compressão uniaxial simples e cíclica, absorção de água, permeabilidade e empuxo conforme as normas vigentes e métodos utilizados pela literatura corrente. Utilizou-se uma gama variada de massas específicas de EPS (10, 15, 20, 25 e 30 kg/m3), incluindo duas recicladas (10 e 12,5 kg/m³). Os principais resultados mostram que os parâmetros de resistência ao cisalhamento direto apresentam variações crescentes conforme aumenta-se a massa específica, assim como os valores de resistência à compressão simples e cíclica. O mesmo é valido para o módulo de elasticidade, que também aumenta com a massa específica. As amostras de baixa massa específica apresentaram um significante intercepto coesivo, enquanto que as maiores possuem elevada parcela de ângulo de atrito. Os parâmetros de absorção de água tendem a diminuir com o aumento da massa específica e todas apresentaram valores muito proximos de permeabilidade. Além disso, valor de 20 kg/m³ é um valor de transição da massa específica com relação ao comportamento das amostras. / Abstract: This work evaluated the properties of expanded polystyrene (EPS) to verify its feasibility and use in geotechnical works. The mechanical and hydraulic properties of the material were studied by tests of direct shear strength, triaxial, simple and cyclic uniaxial compression, water absorption, permeability and thrust according to current standards and methods used in the current literature. A wide range of specific masses (10, 15, 20, 25 and 30 kg/m³) were used, including two recycled (10 and 12.5 kg/m³). The main results show that the direct shear strength parameters show increasing variations as the specific mass increases, as well as the simple and cyclic compressive strength values. The same is true for the modulus of elasticity, which also increases with the specific mass. The samples of low specific mass presented a significant cohesive intercept, while the larger ones had a high proportion of friction angle. Water absorption parameters tend to decrease with increasing specific mass and all presented very close permeability values. In addition, a value of 20 kg/m³ is a specific mass transition value with respect to sample behavior. / Mestre

Det finns idag behov av att ta fram information om hur vatten flödar i marken. För att undersöka detta brukar det installeras grundvattenrör. Grundvattenrör används oftast i syfte att bevaka grundvattennivåer i marken men kan även användas för att utföra hydrauliska tester vars syfte är att skatta jordens hydrauliska egenskaper. Det är då framförallt den hydrauliska konduktiviteten som söks. Kunskap om markens hydrauliska konduktivitet är bland annat viktig för modellering av grundvattenflöden och beräkning av föroreningsspridning. Genom åren har det utvecklats ett antal hydrauliska tester för att ta fram hydrauliska egenskaper i jorden. Från de ursprungliga testerna med pumprör och observationsrör (interferenstester) har det tillkommit metoder för att genomföra tester i enskilda grundvattenrör. Idag kan bland annat pumptest och slugtest genomföras för att skatta hydrauliska egenskaper i enskilda grundvattenrör. Examensarbetet har undersökt olika hydrauliska tester som genomförs i enskilt grundvattenrör. Testerna har varit pumptest, injektionstest, slugtest med solid slug, slugtest med vatten och stigningsmätning. Testerna har genomförts i 11 olika grundvattenrör. Grundvattenrören har varit placerade i olika jordarter och akvifertyper. Alla tester har gjorts i alla rör för att kunna göra en jämförelse mellan testerna. Resultat från testerna visar att det föreligger en variation i skattade hydrauliska egenskaper när en jämförelse gjordes mellan alla slugtester och alla pumptester. Pumptesterna gav generellt en mindre variation mellan test och modellösning och visar sig därför mer oberoende av testtyp och val av modellösning. Slugtesterna visade skillnad i skattad hydraulisk konduktivitet beroende på modellösning. Modellösningarna Hyder mfl. (1994)/KGS och Dougherty-Babu (1984) för slugtest gav en högre skattning hydraulisk konduktivitet än pumptesterna medan modellösningen Bouwer-Rice (1976) gav en lägre skattning av hydraulisk konduktivitet än pumptesterna. Testerna skiljer sig åt när de genomförs i olika jordarter. I lågkonduktiva jordarter är det svårt att genomföra olika typer av pumptest då dessa är påverkade av brunnsmagasin och det krävs att pumpflödet är tillräckligt lågt för att grundvattenröret inte ska torrläggas eller svämma över. Därför är det rekommenderat att utföra slugtest i lågkonduktiva jordarter. I högkonduktiva jordarter är det rekommenderat att göra pumptester då slugtester genererar färre mätpunkter och kan därför leda till fel i modelleringen. / There is a need today to gain information on how water moves in the ground. Groundwater pipes are therefore installed to monitor the groundwater levels. These groundwater pipes can however be used to perform hydraulic tests to obtain information regarding hydraulic properties of the soil. Hydraulic tests are usually performed to investigate the water flow in the soil. This water flow is called hydraulic conductivity. Information on hydraulic conductivity is, for example, essential in modeling of pollutant transport. Several types of hydraulic tests have been developed throughout history in the purpose to investigate hydraulic properties in the soil. The original tests involved pumping tests where one pipe was pumped while an adjacent pipe was used to monitor water level changes. From these original pumping tests there has been a development where the methods can be applied in a single groundwater pipe. Typical single-well tests used today are pumping tests and slug tests. This thesis has investigated and evaluated different hydraulic test performed in single groundwater pipes. Two types of pumping test have been performed: pumping test with constant flow, where the water is pumped out from the pipe, and injection test where water is pumped into the pipe with a constant flow. Three types of slug test have been performed: slug test using a solid slug, slug test using water and rising head test. Slug test is a test where the water level in the pipe is rapidly lowered or raised. The time it takes for the water to return to the initial water level is measured and used to calculate the hydraulic conductivity of the soil. The tests have been performed in 11 different groundwater monitoring pipes. The groundwater pipes were situated in different types of soil and aquifers. All the tests were performed in all the pipes to be able to compare them. Different model solutions were used to analyze the measured data from the hydraulic tests. The results showed variation in estimated hydraulic conductivity when the average hydraulic conductivity of pumping tests and slug tests were compared. The different types of pumping tests had on average a small difference in hydraulic conductivity and the results were on average independent of model solution used. Depending on the model solution there was a difference in hydraulic conductivity for the slug tests. The model solutions of Hyder et al (1994)/KGS and Dougherty-Babu (1984) for slug test estimated over-all a higher hydraulic conductivity than the pumping tests while the model solution of Bouwer-Rice (1976) estimated over-all a lower hydraulic conductivity than the pumping tests. The results and performance of the tests behaved differently depending on the type of soil. It was difficult to perform pumping and injection tests in low conductivity soils due to well-bore storage in the groundwater pipe. It is therefore recommended to perform slug tests in low conductivity soils and pumping tests in high conductivity soil because slug tests generates fewer measurements than pumping tests and can cause errors in the modeling.

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