This book develops the basic ideas of transport models in hydrogeology, including diffusion-dispersion processes, advection, and adsorption or reaction. While balancing the mathematical and physical concepts, it is written in a scientific pedagogical style that is accessible to graduate students and researchers in applied mathematics, the geosciences, civil engineering, and other environmental sciences. The book is organized into six chapters that focus on the diffusion equation, the transport of contaminants and other solutes through porous media, the existence of traveling wave fronts in such systems, filtration theory, the kinematics and dynamics of ground water transport, and the flow and reactions in permeable rocks.Analytic methods for both elementary linear and nonlinear partial differential equations are discussed in detail. Appendices develop numerical methods for partial differential equations, including the method of lines and finite difference methods, and numerical methods for inverting Laplace transforms. Exercises are interspersed throughout the book and over one hundred and twenty references are cited. The book serves as an excellent text or supplementary reading in courses in applied mathematics, contaminant hydrology, ground water modeling, or hydrogeology.