The regulation of water use and water management has evolved considerably in recent years. The evolution of water regulatory systems includes the design of new management policies, which could benefit from ex-ante comparative impact assessments with regard to those of current or past practices. To this aim, the MAELIA project develops an integrated modelling and simulation platform for the assessment of alternative water management policies, especially during low-water crisis in the Adour-Garonne basin (South-West region of France). The development of such an integrated assessment and modelling platform requires the consideration and integration of many entities and processes involved in the system under consideration - water resources and flows, agricultural structures and activities, state and evolution of land cover and land use, etc. This article focuses on the formal representation of two alternative options regarding the choice of water withdrawal policy, which are likely to have considerable impacts on the whole socio-hydro-system s: management by rate of flow (currently applied); and management by volume quotas (alternative to be assessed). Furthermore, the article presents a conceptual framework for the integrated modelling of such social-ecological systems together with graphical notations for models' representation.