Quantification and modelling of heterogeneities in aquifers

[摘要] English: The future of modelling of heterogeneity in aquifers is definitively in the designing ofnew in situ testing (hydraulic and mass transport) procedures with new correspondingmathematical models. New trends in mathematical differentiation offer opportunity toexplore more flexible and practical mathematical model solutions. This applies to bothanalytical and numerical modelling. Only a sound understanding of rock structures canclearly pose the problem which will then be used to define hydraulic equations to besolved by mathematical models, and numerical software.The most recent concept of differentiation based on the non-local and non-singularkernel called the generalized Mittag-Leffler function, was employed to reshape the modelof fractured aquifer fractal flow. The solution was successfully applied to experimentaldata collected from four different constant discharge tests.Additionally, a new analytical solution to the fractal flow in a dual media was proposed,where the media could be elastic; heterogeneous; and visco-elastic. The existing dualmedia fractal flow model was modified by replacing the local derivative with the nonlocaloperator (operator with Mittag-Leffler kernel, and Mittag-Leffler-Power law kerne)l.The more accurate numerical scheme known as Upwind was used to numerically solveeach model.Heterogeneity in a typical South African crystalline rock aquifer was assessed. From this,a methodical level for quantifying and modelling heterogeneity in an aquifer wasdeduced. It was demonstrated how spatial heterogeneity in aquifers can be modelledbased on the most commonly available tools and data in mining environment. Thecapability of selected numerical geohydrological softwares were assessed using spatialvariability of hydraulic parameters (hydraulic conductivity and recharge). Geostatisticaltools were specifically applied. Focus was also given to hydro-geochemicalcharacterization by using bivariate scatter plots, Piper and Expanded Durov diagrams,and PHREEQC hydro-geochemical model as complimentary tools to analyse thegroundwater chemistry data to describe different hydro-geochemical process whichprevail in the monitored groundwater system.Three manuscripts have been submitted out this thesis, in top tier journals of theNatural and Applied Sciences.

[发布机构] University of the Free State