The robustness of decentralized regional water systems under climate change

大多数关于气候变化对区域水系统影响的研究基本上假定由一个决策者管理该系统。无论采用自上而下还是自下而上的方法，都建立了一个优化模型，以最大限度地提高整个区域的净效益(最大限度地减少成本)，同时受到各种限制，包括从选定的气候变化情景(情景主导、自上而下)或从一系列可能的气候未来(基于敏感性、自下而上)获得的水文投入。此外，采用基于敏感度的方法，水资源系统相对于这些变化的水文气候条件的稳健性还要求为每个作业目标确定可接受阈值。这些努力是有用的，但它们的范围受到限制，因为无法考虑多个决策者(当局)，最重要的是，无法模拟不断变化的环境中决策者之间的互动。换言之，由于忽视了体制的复杂性，传统的水管理模式在某种程度上脱离了管理和体制现实，这是成功实施适应措施的两个基本因素。然而，例如，在大多数流域，水政策是由经常争夺资源和权力的多个机构制定的。此外，这些机构之间的互动程度并不一致，可能会受到压力，因为气候不再是一成不变的，而且必须调整政策。更具体地说，必须扩大用于评估区域水系统对气候变化的稳健性的自下而上的方法，以考虑到(1)多个决策者，(2)决策者之间不同程度和形式的互动(从低级别协调到充分合作)和(3)一些利益攸关方制定的或与某些业务目标相对应的不精确的阈值。我们的创新之处在于将机构复杂性纳入区域水资源管理模型，以评估各种机构安排在不同气候变化情景下的稳健性。第二个目标是扩展基于敏感度的方法，以便在评估系统的健壮性时能够适应明确的和模糊的可接受阈值。

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.