Implementing the comprehensive Water Framework Directive requires a thorough planning process that consists of several consecutive steps. The least one can say is that it is a challenging task which needs appropriate ICT tools that are able to cope with the complexity of the water system and this planning process. Integrated assessment, participatory processes and the science-policy interface are one of the newer elements in this overall implementation process that have developed greatly thanks to the WFD. Economic methods, models and instruments are integrative to the WFD implementation as well, with such concepts as cost recovery of water resources being central to debate with stakeholders. Economic valuation of natural resources (willingness-to-pay, willingness-to-accept, ...) should get sufficient attention and the human dimension (perception, needs, wants, values and behaviours) should be incorporated in the modelling frameworks for decision-making. In the same line there is also a human dimension to the use of models: how do non-modellers, such as managers, policy-makers, other stakeholders feel about models and their use in their day-to-day activities. And finally, this volume deals with the large issue of data: its quality, availability and, not to forget, accessibility. And can we use data both for monitoring purposes (surveillance, operational and investigative in the WFD context) and for modelling. Is there a synergy to be found?These tasks, the underlying concepts, methods, tools and procedures are the subject of this volume.The Harmoni-CA project partnership consisted of:RIZA, Institute for Inland Water Management and Wastewater Treatment, The NetherlandsBIOMATH, Ghent University, BelguimPIK, The Potsdam Institute for Climate Change Impact Research, Germany GEUS, Geological Survey of Denmark and Greenland, Denmark USF, Institute for Environmental Systems Research, University of Osnabrück, GermanyThe other three volumes in the Water Framework Directive Series are:Water Framework Directive: Model supported Implementation - A Water Manager's Guide edited by Fred Hattermann and Zbigniew W KundzewiczModelling Aspects of Water Framework Directive Implementation - Volume 1 edited by Peter A. VanrolleghemDecision Support for WFD implementation - Volume 3, edited by Peter A. Vanrolleghem