In the urbanised delta of the Netherlands, it is important to take water-related and environmental impacts fully into account when deciding on socio-economic activities. This is the aim behind Water Assessment (WA), Environmental Impact Assessment (EIA) and Strategic Environmental Assessment (SEA). This thesis is centred on a comparative research of these policy instruments. The overall research aim is to ex-plain the character and effectiveness of WA, EIA and SEA, and compare each of them with the others, also in relation to their broader policy context. The method that is used in this thesis is positioned at the intersection of theory and practice. It is a method underpinned, philosophically, in Aristotle‘s phronesis and apagoge. Phronetic research is a context-dependent and reflective analysis of practice, which leads to contributing to that practice. Apagoge refers to retroductive inferences. The method used — the ‗method of articulation‘ — is anchored by these core ideas, which form a base for the research. Articulation is a method that facilitates linking heterogeneous concepts from theory, not only with each other, but also with the prac-tical phenomena that are being studied. In the content perspective, the decisions in relation to WA, EIA and SEA, in which decision-makers balance the socio-economic interests of societal initiatives with the water-related and environmental interests, are conceptualized as ‗trade-offs‘. Un-certainty and ambiguity are inherent to such decision-making processes. In the steer-ing perspective, the umbrella concept for three modes of coordination — markets, hierarchy and networks — is ‗metagovernance‘, while in the planning perspective, the core concepts are rational and communicative planning approaches with a power complement. This set of concepts is used to explain the similarities and differences among WA, EIA and SEA. Second, the effectiveness, strengths and weaknesses of these in-struments are shown, based on several evaluations. Third, these instruments are then positioned within the historical context of Dutch and European water management, environmental and spatial planning policies. The thesis ends by offering practical con-tributions to the further development of WA, EIA and SEA in the Netherlands Water en milieu in besluitvorming: een vergelijking van de watertoets, milieueffectrapportage en strategische milieubeoordeling in de Nederlandse planning. De watertoets is in 2001 geïntroduceerd in de context van een nieuwe benadering op het raakvlak van waterbeheer en ruimtelijke ordening. In deze benadering wordt meer rekening gehouden met de natuurlijke dynamiek van het watersysteem. De m.e.r. bestaat al veel langer, die werd in 1969 in de USA als reactie op milieuproblemen geïntroduceerd. Sinds 1985 verplicht de EU de lidstaten tot toepassing van de m.e.r. Sinds 2001 is er tevens een Europese richtlijn voor SMB. Het doel van m.e.r. en SMB is het milieubelang een volwaardige plaats te geven in die besluitvorming. Behalve vergelijkingen van de instrumenten geeft deze studie tevens een overzicht van evaluaties van watertoets (2006), m.e.r. (Ten Heuvelhof en Nauta, 1996; NovioConsult, 2003; De Valk, 1997) en de historische politieke context