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都假设只有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，都要开发一个优化模型，以在各种约束条件下实现区域范围内净效益最大化（成本最小化），包括来自选定气候变化情景（情景主导，自上而下）或一系列可能的气候未来（基于敏感性，自下而上）的水文输入。此外，采用基于敏感性的方法，水资源系统对-à-vis这些变化的水文气候条件的稳健性也要求为每个操作目标确定可接受的阈值。这些努力是有用的，但由于无法考虑多个决策者（当局），最重要的是，无法模拟决策者在不断变化的环境中的相互作用，它们的范围受到限制。换句话说，由于忽视了制度的复杂性，传统的水管理模式在某种程度上脱离了管理和制度现实，这是成功实施适应措施的两个基本因素。然而，例如，在大多数河流流域，水政策是由许多经常争夺资源和权力的机构制定的。此外，这些机构之间的相互作用程度并不相同，由于气候不再稳定，政策必须调整，因此可能会受到压力。更具体地说，用于评估区域水系统对气候变化的鲁棒性的自下而上方法必须扩展，以考虑(1)多个决策者；(2)决策者之间不同层次和形式的互动（从低水平协调到全面合作）；(3)一些利益相关者制定的不精确阈值或对应于某些运营目标。我们提出的新颖之处在于将制度复杂性纳入区域水资源管理模型，以评估不同气候变化情景下各种制度安排的稳健性。第二个目标是扩展基于灵敏度的方法，以便在评估系统的健壮性时能够适应清晰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.