Intruduction
Numerous studies have demonstrated the paradigm shift made by the WFD in comparison with the previous piecemeal approach of EU water law. Clearly the WFD constitutes a major step in promoting a wider integrated water protection and management process in longer-term perspective 
. The WFD thus promotes an ecosystem approach on the basis of a river basin defined as “the area of land from which all surface run-off flows through a sequence of streams, rivers and possibly, lakes into the sea at a single river mouth, estuary or delta” (article 2). Such a holistic vision integrates the entire water cycle from inland surface waters to coastal waters, including terrestrial ecosystems and wetlands directly depending on the aquatic ecosystems. It also states the complex status of water which is “not a commercial product like other but, rather, a heritage which must be protected, defended and treated as such” (whereas 1)
The WFD set out very ambitious objectives and general obligations in order to achieve a good status for all EU surface waters and groundwater by 2015 (A). The WFD focuses primarily on the protection and the improvement of water quality; as it states, the “control of quantity is an ancillary element in securing good water quality and therefore measures on quantity, serving the objective of ensuring good quality should be establish” (19).
Everyone recognises the highly technical nature of the WFD, in particular the numerous annexes reflecting an understanding of the functioning of water bodies that remains subject to scientific debate. Numerous guidance documents (non-binding) on the implementation of the WFD have been drawn up by the Commission in cooperation with the representatives of Member States . Not surprisingly, the CJEU has been called upon to clarify different provisions of the WFD. The WFD includes a large number of listings and of cross-references from one provision to the other, a high number of definitions, sometimes on basic geographical notions such as those of river or lake, as well as on a series of concepts pertaining to the “status” of water bodies. These concepts are hardly self-explanatory although essential to its half a dozen “characteristics” (Article 5). Most of the Directive’s provisions, however, leave a wide margin of discretion as to the nature of the measures to be taken because it does not aim at a complete harmonisation of water laws . However, Member States must ensure that the transposition of the WFD is sufficiently clear and precise. Many of the complex definitions set out in the WFD are thus “essential” for ensuring the correct transposition and implementation of the directive. In case C-648/13 , the Court declared that Poland had failed to transpose completely and correctly the definitions of “groundwater status”, “good groundwater status”, “quantitative status” and “available groundwater resource”.
The WFD has as a dual dimension: on the one hand, it provides a set of “strategies” for the enactment of implementation directives pertaining to miscellaneous pollutants and affected environments while, on the other, it includes immediately applicable provisions . The WFD imposes various specific obligations on Member States, from characterisation of rivers basins to multi-annual planning and the recovery of the costs of water services (B). The specific quality objectives allowing water bodies to be so characterised reflect both pollution prevention and the quest for a “good” water status with certain nuances for surface waters and for groundwater (C). The WFD promotes a certain model of governance of river basin districts and of the participation of the general public including users of water and local authorities which need to be improved (D). Finally, the WFD provides the possibility of less stringent environmental objectives, derogations and deadline extensions that constitutes a veritable nest of disputes (E). The implementation of the WFD is the source of a large number of disputes brought before the CJEU; over the last 5 years, 10 cases illustrate the main difficulties related to the complete implementation of this complex Directive.