Although generally accepted as a necessary step to improve water management and planning, integrated water resources management (IWRM) methodology does not provide a clear definition of what should be integrated. The various water-related issues that IWRM might encompass are well documented in the literature, but they are generally addressed separately. Therefore, water management lacks a holistic, systems-based description, with a special emphasis on the interrelations between issues. This article presents such a system model for water management, including a graphical representation and textual descriptions of the various water issues, their components, and their interactions. This model is seen as an aide-memoire and a generic reference, providing background knowledge helping to elicit actual system definitions, in possible combination with other participatory systems approaches. The applicability of the model is demonstrated through its application to two test case studies.