Résumé
Societies' interactions with their environment are mediated through techniques and institutions. Where water is a crucial element of livelihoods and where landscapes are substantially shaped by water resource development interventions these interactions are made more complex by the interconnectedness of users through the hydrologic cycle entailed by their dependence upon the same resource. The hydrologic cycle connects users and ecosystems across scales and allows externalities -expressed in terms of altered water quantity, quality, sediment load or timing- to travel across space, time and social groups. As pressure over resources increases and river basins "close" this interdependence becomes more critical, increasing the frequency and seriousness of water shortages and conflicts.The paper proposes a generic model of aquatic socio-ecological systems which accounts for these interlinkages across nested scales, from the user, to the distribution system (e.g. a city or an irrigation scheme), catchments and river basins, throughout to wider socio-economic and political spheres. The model adopts a political ecology framework and emphasizes that interactions and cross-scale dependences are not just physical but also include discursive and political dimensions of power.