Climate change and the current context of environmental crises are prompting those involved in water resource management to rethink the hydrological systems inherited from past centuries. As an international reference, the evolution of hydrological knowledge of the Seine is an exemplary field of investigation for shedding light on a whole area of the history of hydraulic sciences and techniques. It also enables us to understand the genesis and development of public policies dedicated to flood and low-water control on the scale of a catchment area with major urban issues at stake. Covering the last four centuries, this book highlights the turning points in knowledge, representations and technical management of the Seine basin upstream of Paris. In particular, it shows the importance of the “Belgrand model”, established in the mid-nineteenth century, and the key role played by the construction of reservoir dams in defending Paris against flooding.