Nowadays water quality issues in terms of diffuse nitrogen pollution are challenging to local water resources management in Europe, particularly in the agriculture-intensive countries. The investigation of these challenges would be valuable. In this book, Denmark was selected as a typical study case for this purpose. By utilising transition theory for an analytical framework, the author tried to provide a systematic way to look insight into the identified problems. After introducing a new concept “nitrogen lock-in”, the study argues that the current Danish nitrogen lock-in is actually the result of the competition between constructive forces and destructive forces from different stakeholders. Future breakthrough depends on whether innovative approaches for both water management and economic growth can be harmoniously integrated. The author hoped this book can provide a new angle to look at the challenges we met in water management, and can provide, to some extent, a piece of reference for future water management research.