The robustness of decentralized regional water systems under climate change

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Most of the studies dealing with the impact of climate change on regional water systems essentially assume that a single decision maker manages the system. Whether a top-down or a bottom-up approach is implemented, an optimization model is developed to maximize region-wide net benefits (minimizing costs) subject to various constraints including hydrologic inputs derived from selected climate change scenarios (scenario-led, top-down) or from a range of possible climate futures (sensitivity-based, bottom-up). Moreover, with the sensitivity-based approach, the robustness of the water resources system vis-à-vis those varying hydro-climatic conditions also require that acceptability thresholds be defined for each operating objective. These efforts have been useful but their scope is limited by the inability to consider multiple decision makers (authorities) and, most importantly, the inability to simulate the interactions among the decision makers in a changing environment. In other words, by ignoring institutional complexity, traditional water management models are somehow divorced from managerial and institutional realities, two essential factors for the successful implementation of adaptation measures. Yet, in most river basins, for instance, water policies are derived from a multiplicity of institutions often competing for resources and authority. In addition, the level of interaction between these institutions is not homogeneous and will likely be under stress as the climate is no longer stationary and as policies must be adapted. More specifically, the bottom-up approach used to assess the robustness of regional water systems to climate change must be extended to account for (1) multiple decision makers, (2) various levels and forms of interaction among the decision makers (from low-level coordination to full cooperation) and (3) imprecise thresholds formulated by some stakeholders or corresponding to certain operating objectives. What we offer as novel is the incorporation of institutional complexity into regional water resources management models, in order to assess the robustness of various institutional arrangements under different climate change scenarios. A secondary objective is to extend the sensitivity-based approach so that it can accommodate crisp and fuzzy acceptability thresholds when assessing the robustness of the system.