INTEGRATED APPROACHES FOR SCALABLE AQUIFER NUMERICAL MODELING, INVERSION, AND UPSCALING

Abstract

In this dissertation, three interconnecting research themes in the domain of groundwater modeling and characterization are explored. The dissertation represents a significant integration of novel approaches and computational tools for groundwater modeling and characterization. It not only improves our current understanding but also presents considerable new directions for future study, making a significant contribution to groundwater modeling. Chapter 2 focuses on the development of a distinctive joint-inversion methodology, which utilizes hydrogeological, self-potential, and magnetotellurics data, to estimate hydraulic conductivity and electrical resistivity. The proposed technique doesn't necessitate any assumptions related to petrophysical relationships and demonstrates a 25\% improvement in the estimation of hydraulic conductivity in comparison to single data-type inversions, providing crucial insights into regions beyond immediate observation wells. In Chapter 3, a significant focus is placed on developing a reliable hydraulic conductivity upscaling tool for high-dimensional groundwater flow models. Recognizing the vital role of accurately representing hydraulic conductivity at an appropriate scale, the study strived to develop a computational tool that effectively balances computational efficiency while preserving key features of the detailed hydraulic conductivity field. The tool, based on Kitanidis' (1990) hydraulic conductivity upscaling approach, has the capability to calculate upscaled hydraulic conductivity values in the tensor form and account for anisotropy. Rigorous tests were carried out to assess the performance of the tool, and its resilience under various flow conditions, providing a reliable resource for high-dimensional groundwater modeling. Chapter 4 addresses the development of the PISALE software. This tool is specifically designed to manage the complexities of groundwater flow processes in Pacific islands that are marked by dynamic interactions between freshwater and seawater in highly heterogeneous volcanic rocks. The software integrates advanced mathematical techniques and parallel programming models to accelerate solutions and offer precision in reproducing freshwater-seawater interfaces in large-scale coastal aquifers.