A dynamic framework for water security

Water security is a multi-faceted problem, going beyond mere balancing of supply and demand. Early attempts to quantify water security relied on static index-based approaches that failed to acknowledge that human action is intrinsic to the water cycle. Human adaptation to environmental change and increasing spatial specialization in the modern world necessitate a more flexible and dynamic view of water security. Starting from first principles, and through application of simple water balance concepts to human-impacted water systems, we first develop a set of indicators for water insecurity. We then offer an approach to model these indicators as outcomes of coupled human-water systems to anticipate watershed trajectories under human impacts, predict water insecurity, and inform appropriate action. In this way, far from being a static index, water security signifies a “safe operating subspace” within a three-dimensional space that maps physical resource availability, infrastructure, and economic choices.