Groundwater seepage is a key question for many engineering applications, such as open-pit mining, design of underground tunnels and hydraulic structures, such as tailing and earth dams. The underground flow of water can create significant problems for land drainage. Seepage problems concern the percolation of water through dams and into excavations, and the movement of water into and through the soil from bodies of surface water. Dam safety, environmental remedial works and mineral location normally involve comparatively expensive techniques but if the extent and location of groundwater seepage can be accurately predicted then the amount of works and thus costs can be dramatically reduced. The changes in the seepage region could be effectively reflected through the analysis of the groundwater age using parametric simulation analyses. In this book, seepage through an earth-fill dam s body is investigated using a software model since seepage both in the dam's body and under the foundation adversely affects dams stability.