水安全问题是人类面临的最复杂，最棘手的问题之一。每年，估计有40亿人经历至少一个月的缺水状态，而且随着全球气候的不断变化，水安全可能会成为人们必须要面对的更加严重和普遍的问题。在城市，尤其是在城市中心区，其应对缺水和洪涝等水安全问题的脆弱性更大。人口增长和城市化的双重过程将导致对水需求的增加。但是，许多城市都面临经济和资源两个方面的限制，这主要体现在对有效满足其对水需求增长的能力的限制，尤其是在可供应的水资源量减少的情况下。因此，当务之急是城市需要有效地管理雨水，尽可能收集雨水增加供水量，同时提高抵御城市洪灾和改善水环境的能力。尽管雨水回用作为降低成本，增加供水量和保护城市水环境的一种方法得到国际上广泛的关注，但仍缺乏定量分析雨水饮用水回用与非饮用水回用模式及其不同配置情况下回用成本和收益的研究，例如集中式回用和分散式回用。本论文综合利用经济成本、能源消耗和淡水资源节省等指标，分析了雨水集中式饮用回用和分散式非饮用回用模式的成本和收益。并以美国德克萨斯州的休斯敦市的Hunting Bayou流域作为研究区，开展了相应案例研究。首先基于Vflo和HEC-RAS分别建立了研究流域的水文和水动力模型，通过模拟流域产流来确定不同雨水利用情景下集中式雨水回用设施的规模和每年可以收集的雨水量。进而利用本流域的历史降雨和需水量数据进一步评估了需要收集的水量。同时利用文献中得到的经济成本和能耗数据分析了不同回用模式的成本和能耗。最后利用层次分析法（AHP）对雨水回用情景进行了分析和排序。论文结果显示将分散式非饮用回用与集中式饮用回用相结合可以得到最大的收益。按照年计算，该情景可以收集雨水950万 ft3，成本花费 4670万美元和消耗2.6 × 107 kWh 能源。世界各地的城市在计划开展雨水回用工作以增加其供水量和提升其适应能力时，均可借鉴本方法。
Water insecurity is one of the most complex and vexing issues facing humanity. Every year, an estimated 4 billion people experience water scarcity for a period of at least one month, and, as the earth’s climate continues to change, water insecurity will likely become a more severe, widespread problem. Cities and urban centers are especially vulnerable. The dual processes of population growth and urbanization result in increased demand for water. However, many cities face economic and resource constraints which inhibit their ability to effectively meet increasing demand for water, especially in the face of decreasing supply. It is therefore imperative that cities effectively manage their stormwater, and stormwater reuse is a viable option to augment water supply, combat urban flooding, and prevent the occurrence of the urban stream syndrome. Despite the attractiveness of stormwater reuse as a means to decrease costs, augment water supply, and protect urban streams, there is a dearth of research quantitatively analyzing the costs and benefits of potable vs. non-potable stormwater reuse as well as reuse under different configurations, such as centralized and decentralized. This thesis analyzes the costs and benefits of centralized, potable and decentralized, non-potable stormwater reuse, using financial costs, energy consumption, and the volume of freshwater withdrawals saved as indicators. The Hunting Bayou watershed in the city of Houston in Texas, USA is used as the study area. The hydrologic and hydraulic models, Vflo and HEC-RAS were used to analyze rainfall runoff in the watershed to determine both the size of the centralized stormwater reuse infrastructure and to determine the volume of water that could be captured annually in the watershed under different stormwater reuse scenarios. Historical rainfall and water demand were evaluated to further understand the retention volume needed. Energy consumption and financial cost data were obtained from the literature. The Analytic Hierarchy Process (AHP) was used to prioritize the best reuse scenario. The results of this thesis indicate that a combined configuration of both decentralized, non-potable and centralized, potable reuse would provide the most benefits to the watershed. On an annual basis, this scenario is estimated to capture 9.5 million ft3, to cost $46.7 million, and to consume 2.6 × 107 kWh of energy. This methodology can be employed by cities around the world as they take the first step in planning for stormwater reuse to augment their water supply and increase their resiliency.
