Switching off the pumps of a mine is one of the last steps in the lifetime of a surface or underground mine. As the water in the open space raises, the water might become contaminated with different pollutants and eventually starts to flow in the open voids. This book addresses the processes related to mine abandonment from a hydrogeological perspective. After an introduction to the relevant hydrogeochemical processes the book gives detailed information about mine closure procedures. Based on in-situ measurements the hydrodynamic processes in a flooded mine are described and some of the mine closure flow models exemplified. As all investigations base on precise data, the book gives some key issues of monitoring and sampling, especially flow monitoring. Then the book shows some new methodologies for conducting tracer tests in flooded mines and gives some hints to passive mine water treatment. At the end 13 well investigated case studies of flooded underground mine and mine water tracer tests are described and interpreted from a hydrodynamic point of view.