This book systematically introduces theories, methods, and applications of modeling contaminant transport in groundwater. It can be used as a textbook at the graduate level or a reference book for hydrogeologists, geochemists, petroleum engineers, and environmental engineers. It is also an interesting book for applied mathematicians. The book covers all main aspects and the latest developments in the field of groundwater quality modeling. The major emphasis is on solving practical three-dimensional advection-dispersion problems. The FORTRAN program which is given in the appendix can be used to simulate contaminant transport in either steady state or transient flow fields. This program is useful for teaching as well as for solving practical problems. The program is available for teachers from Springer via our web site. TOC: Contents: Introduction.- Hydrodynamic Dispersion in Porous Media.- Analytical Solutions of Hydrodynamic Dispersion Equations.- Finite Difference Methods and the Method of Characteristics for Hydrodynamic Dispersion Equations.- Finite Element Methods for Solving Hydrodynamic Dispersion Equations.- Numerical Solutions of Advection-Dominated Problems.- Mathematical Models of Groundwater Quality.- Applications of Groundwater Quality Models.- Conclusions.- Appendix A: The Related Parameters in the Modeling of Mass Transport in Porous Media.- Appendix B: A FORTRAN Program for Simultaneously Simulating Groundwater Flow and Quality.- References.