This article explores the reasons efforts to attain water security by states and the international water policy community often fall short of their goals, and suggests a conceptual tool as partial remedy. The main shortcomings of prevailing water security policy and thinking are found to stem from narrow and determinist analysis that is based on a separation of biophysical and social processes of water resources and their use. Undue confidence is placed in physical scarcity thresholds, for example, while distributive issues are ignored. Water resources are also found to be treated in isolation, as if independent of the food, climate or energy security of individuals, communities and states. The ‘web’ of water security introduced here emphasises combined readings of the social and biophysical processes that enable or prevent national water security. These processes are mediated by a socioeconomic and political context replete with power asymmetries, such that water security for some rests on the water insecurity of others. Sustainable national water security in the long term, it is suggested, will be guided by principles of balance between related security areas, and equitability of distribution of resources between the actors involved.