Understanding water circulation in rocks represents a very important element to solving many of the problems linked with civil, environmental and mining engineering. This book offers a synthesis of the actual knowledge about the fluid flow in rocks: - from the medium characterization and the structural geological survey to the generation of stereonets; - the evaluation of the hydrogeological parameters using either deterministic or probabilistic methodologies; - the evaluation of the preferential flow direction considering the change of the hydrogeological structures; - the methods and models used to simulate the flows. Three case studies are provided; water circulation and slope instability, hydrogeological risk linked with tunnelling,