The rationale of this project is the increasing need for improved tools supporting water management at the catchment level as required by different national and international legislations. In 2000, the Water Framework Directive has been introduced in Europe which set the political frame for implementing Integrated Water Management (IWM) at the catchment level. The final aim of the directive is to reach a good ecological status of European water bodies by 2015 by means of IWM, which can be supported by water quantity and quality modelling. The European Commission is currently also preparing a directive on the assessment and management of floods. This new directive will aim at the reduction and the management of the risks that floods pose on human health, the environment, and the infrastructure. Since 1998, floods in Europe caused approximately 700 deaths, a displacement of about half a million people and at least €25 billion in insured economic losses. As it is foreseen that in the coming decades the risk for flooding will be higher, and the economic damage will increase, appropriate measures are needed that can reduce its likelihood, or limit its impacts. These measures should be based on a thorough understanding of the impact of management measures on the hydrologic and hydraulic functioning of catchments.