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Embracing Uncertainty as the New Norm: A Risk-Based Portfolio Approach for Urban Water Investment Planning.

机译：将不确定性作为新准则：城市水投资规划中基于风险的投资组合方法。

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摘要

Providing secure and reliable water supply service to major urban areas has become a considerable challenge in recent years on a global basis. Rapid population growth, urbanization and development needs put enormous pressure on water resource managers to satisfy the ever-growing demand. Climate change, in addition to the inherent variability in hydrological cycles, adds another layer of deep uncertainty to forecast surface water availability. Many major cities have observed declining reservoir storages during unprecedented droughts. The once-reliable reservoir storage systems can no longer serve its purpose. During extended period of water shortages, urban residents and businesses suffered from mandatory water restrictions, causing large economic and social welfare losses. Facing these challenges, water utilities and governments make large investments in supply augmentation infrastructure, which have long-term consequences that can shape development for decades. However, the increasing complexity of uncertainty suggests that the ability to predict the future is limited; hence, there is a need to shift from the conventional "predict-then-act" planning paradigm. This thesis presents an alternative framework to urban water investment planning, using a portfolio approach.;A generalized risk-based framework for urban water supply-demand planning is proposed, and it is applied to Melbourne, Australia, to demonstrate its utility and usefulness. First of all, water shortage risk is clearly defined in two terms--frequency and severity of water shortages--of a defined planning horizon. Supply-side uncertainty is quantified based on probability distributions of precipitation and runoff to reservoirs. Demand-side uncertainty is modeled by scenarios with different combinations of population growth rate and per capita water usage. Next, the thesis presents an investment decision-making tool to identify cost-effective supply-demand portfolios that minimize water shortage severity while achieving a target level of reliable service. In addition to find the optimal portfolio composition, the model presents sequences of investments, indicating timing of implementation of each chosen measure. Using mixed integer programming, the decision-making tool yields Pareto efficient frontiers for different demand scenarios. The Pareto frontier exhibits trade-offs between cost of a water supply-demand strategy and water shortage risks facing a society in the long run. The trade-offs provide analytical insights on risk attitude towards water supply services, namely (i) what is the acceptable level of water shortage risk for a society, and (ii) how much are customers willing to pay to avoid such a risk. The results indicate that a portfolio which diversity risk of individual supply augmentation and conservation measures is robust when confronting a wide range of plausible climate and demand growth scenarios. Finally, recognizing important roles played by society and government in water-related investment decision-making process, the thesis discusses institutional barriers in adopting and implementing the proposed risk-based framework in practice.;This thesis presents an alternative framework to quantitatively integrate risk in urban water resources management. Under this framework, the portfolio approach is an analytical tool for decision-makers to prioritize investments in supply augmentation infrastructure and implementation of demand management programs. It is the hope of the author that this work provides new insights and necessary tools to water sector professionals in urban water investment planning. The use of risk-based framework and portfolio approach is not limited to any specific city and could find many applications in urban areas where water scarcity and climate risk are pressing issues.
机译：在全球范围内，近年来，向主要城市地区提供安全可靠的供水服务已成为一项巨大的挑战。快速的人口增长，城市化和发展需求给水资源管理者带来了巨大的压力，以满足不断增长的需求。除了水文循环固有的可变性之外，气候变化还为预测地表水的可利用性增加了另一层深层的不确定性。许多大城市在史无前例的干旱期间观察到水库的储量正在下降。曾经可靠的水库存储系统不再能满足其目的。在长期的缺水时期，城市居民和企业受到强制性的用水限制，造成了巨大的经济和社会福利损失。面对这些挑战，自来水公司和政府在增加供应基础设施上进行了大量投资，这些长期影响可能影响数十年的发展。但是，不确定性的复杂性不断增加，表明预测未来的能力是有限的。因此，有必要从传统的“先行后行”计划范式转变。本文提出了一种利用投资组合的方法来替代城市水投资规划的框架。提出了一种基于风险的广义城市水供需规划框架，并将其应用于澳大利亚的墨尔本，以证明其实用性和实用性。首先，在定义的规划范围内，用两个术语（缺水的频率和严重性）明确定义了缺水风险。供应方的不确定性是根据降水和水库径流的概率分布来量化的。需求方的不确定性是根据人口增长率和人均用水量不同组合的情景建模的。接下来，本文提出了一种投资决策工具，用于确定具有成本效益的供需组合，以最大限度地减少缺水严重性，同时达到可靠服务的目标水平。除了找到最佳的投资组合构成之外，该模型还显示了投资顺序，指示了每种所选度量的实施时间。使用混合整数编程，决策工具可以为不同需求场景提供Pareto有效边界。帕累托边界展现了供需战略成本与长期社会面临的缺水风险之间的权衡。权衡可以提供关于供水服务风险态度的分析见解，即（i）社会可接受的缺水风险水平是多少，以及（ii）顾客愿意为避免这种风险付出多少。结果表明，当面对各种可能的气候和需求增长情景时，具有单个供应增加和保护措施的多样性风险的投资组合是强大的。最后，认识到社会和政府在与水有关的投资决策过程中的重要作用，本文讨论了在实践中采用和实施拟议的基于风险的框架的制度障碍。城市水资源管理。在此框架下，投资组合方法是决策者优先考虑对增加供应基础设施和实施需求管理计划进行投资的一种分析工具。作者希望这项工作为城市水投资规划中的水务专业人员提供新的见识和必要的工具。基于风险的框架和投资组合方法的使用不限于任何特定的城市，并且可以在缺水和气候风险成为紧迫问题的城市地区找到许多应用。

著录项

  • 作者

    Zhang, Chengyan.;

  • 作者单位

    Harvard University.;

  • 授予单位 Harvard University.;
  • 学科 Environmental engineering.;Urban planning.;Economics.
  • 学位 Ph.D.
  • 年度 2016
  • 页码 194 p.
  • 总页数 194
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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