Abstract The rapidly growing urban centres throughout the world are facing serious problems due to the fast-changing developments in all of their environmental spheres (nature, society, politics, culture and economics). Therefore, strategic planning becomes even more important in order to develop strategies that allow cities to adapt to new challenges and to prevent or to mitigate negative trends. This paper presents a transdisciplinary approach to water management, which combines adaptation and application of methods from hydrology, social sciences, water engineering and modelling; furthermore, this approach also involves stakeholders in this process. This methodology assists cities in addressing risks by elaborating solutions, which are characterised by ownership and acceptance of the stakeholders involved. The presented methodology proposed here has been applied to the water system of the desert megacity of Lima/Peru. As a city of almost 10 million inhabitants and with an annual rainfall of about 10 mm per year, Lima presents a unique case with particular challenges regarding water supply. In order to assess the changes in precipitation and temperature for the next decades, two global circulation models and three scenarios have been used. Changes in discharge was addressed using the conceptual rainfall-runoff model HBV applied in both the Atlantic and Pacific catchments relevant to the capital city Lima in terms of water supply. A scenario methodology, combining qualitative and quantitative elements, based on the Cross-Impact Balance Analysis, has been developed and applied. From the millions of theoretically possible combinations of future developments of “descriptors” (driving forces) of the water system, four have been identified as the (only) consistent potential developments of the future. Local stakeholders, stemming from a wide range of institutions have been actively involved in the definition of these driving forces and the set of scenarios. The evaluation of these scenarios and potential options to adapt the water system to future developments was carried out by modelling and simulation, using a purpose-built, yet general, simulator which represents the entire water and wastewater system and includes the important inherent feedback loops (e.g. water demand by irrigation, reuse of treated and untreated wastewaters). The setup of the simulator and the implemented models was done in a way that the simulator formed an integral element in the design of strategies and measures, derived by this innovative combination of qualitative scenario building, quantitative modelling and stakeholder participation. As a core result of this process, the Action Plan “Lima 2040” has been developed and adopted, in which the signatories (the main institutions and organisations responsible for the water sector of Lima) commit themselves to specific actions to be implemented over the years to come.

中文翻译：

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特大城市供水系统的综合建模——跨学科方法在利马大都市区的应用

摘要 由于所有环境领域（自然、社会、政治、文化和经济）的快速发展，世界各地快速发展的城市中心正面临着严重的问题。因此，为了制定使城市适应新挑战并防止或减轻负面趋势的战略，战略规划变得更加重要。本文提出了一种跨学科的水管理方法，它结合了水文学、社会科学、水工程和建模方法的适应和应用；此外，这种方法也让利益攸关方参与到这一过程中。这种方法通过制定解决方案来帮助城市解决风险，这些解决方案的特点是相关利益相关者的所有权和接受度。这里提出的方法已应用于利马/秘鲁沙漠特大城市的水系统。作为一个拥有近 1000 万居民且年降雨量约为 10 毫米的城市，利马是一个独特的案例，在供水方面面临着特殊的挑战。为了评估未来几十年降水和温度的变化，使用了两个全球环流模型和三个情景。使用在与首都利马相关的大西洋和太平洋集水区在供水方面应用的概念性降雨-径流模型 HBV 解决了排放量的变化。已经开发并应用了一种基于交叉影响平衡分析的结合定性和定量要素的情景方法。从水系统“描述符”（驱动力）的未来发展的数百万个理论上可能的组合中，有四个已被确定为（唯一）一致的未来潜在发展。来自各种机构的当地利益相关者一直积极参与这些驱动力的定义和情景设置。这些情景和使水系统适应未来发展的潜在选项的评估是通过建模和模拟进行的，使用了一个专门构建的通用模拟器，该模拟器代表整个水和废水系统并包括重要的固有反馈回路（例如灌溉需水量、处理过和未处理过的废水的再利用）。模拟器和实施模型的设置方式使模拟器成为战略和措施设计中不可或缺的元素，这是通过定性场景构建、定量建模和利益相关者参与的创新组合衍生出来的。作为这一过程的核心结果，制定并通过了“利马 2040”行动计划，其中签署方（负责利马水务部门的主要机构和组织）承诺将在多年来实施的具体行动来。