Examining the numerical modeling of sub-surface systems, this comprehensive work studies fluid flow in saturated groundwater-flow and geothermal systems. It compiles and synthesizes the modern features as well as reviews the related solute and heat transport. This forward-looking volume addresses barriers to progress in this area and provides new insight into methods to achieve advancement. Real case studies supplement the material along with practical applications of theoretical examples. Jochen Bundschuh, the editor of this work, is the co-director of the Latin-American Centre for Groundwater Research, and he is world-renowned for his studies on groundwater arsenic.