Collaborative Research: Urban Watershed Evolution - Novel Temporal Perspectives on the Hydrologic Impacts and Positive Unintended Consequences of Failing Municipal Infrastructure

市政当局面临着越来越多的挑战，需要使用老化和失效的基础设施来提供持续的清洁水供应，并回收和处理废水，但人们对基础设施何时、何地、如何开始出现故障或如何发展知之甚少。该项目有三个主要的科学目标，包括：1)确定市政用水离开工程系统进入自然水文系统后的命运；2)揭示基础设施在什么时候、在什么条件下开始出现故障；3)了解这种故障及其对水资源的影响是如何随着时间的推移而发展的。主要的项目活动包括使用溪流和树木中的天然化学示踪剂重建水质历史，并使用历史数据重建基础设施发展历史。我们希望我们的方法可以转移到其他城市系统老化的基础设施。更广泛地说，该项目将利用我们的利益相关者网络，帮助为城市层面的规划工作提供信息，以实施有弹性的基础设施，同时适应21世纪城市人口的快速增长。该项目的成果将被纳入德克萨斯大学奥斯汀分校的可持续发展课程，其中包括跨学科学位和24门强调实地经验的课程，每年有800名学生在拟议的河流研究地点进行校园环境研究，以及德克萨斯大学奥斯汀分校和亚利桑那大学的地球科学研究生课程。研究生和本科生的培训将强调纳入代表性不足的少数民族。在奥斯汀每个流域的基础设施出现故障时，市政用水通过渗漏进入相对原始的自然水文系统。我们假设，这些人为水源的独特化学成分记录在秃柏树在失败的开始和随后几年的失败进展。本项目采用天然同位素示踪剂的新方法，在同一水文地质地形的三个流域研究城市化对自然水文和河流生态的影响。流域间的主要变量是城市化程度。我们将分析溪流中的元素和Sr同位素变化，并开发高分辨率测量方法，测量生长在这些溪流附近的秃柏树生长年轮中的Sr同位素。我们假设树木年轮的生长速率和同位素组成编码了基础设施逐渐失效的水文历史。我们将利用水文地球化学模型应用这些数据：1)在人为破坏的流域中，追踪城市用水在自然水文循环中的演变；2)利用树木化学变化来重建城市输入水的年代际变化。这些结果将首次用于确定基础设施故障发生的时间以及故障的大小和影响的时间变化。我们将把这一城市用水输入的时间记录与同一流域的城市发展历史进行比较，以确定城市化程度的阈值，超过这个阈值，基础设施失败对水文和生态的影响就会显现出来。该奖项由水文科学、环境可持续性和环境工程项目共同资助。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Municipalities are increasingly challenged to use aged and failing infrastructure to deliver a continuous supply of clean water, and to return and treat wastewater, yet little is known about when, where, and how infrastructure failures were initiated or how they progressed. This project has three main scientific goals including: 1) determining the fate of municipal water after it leaves the engineered system and enters the natural hydrologic system, 2) unravel when, and under what conditions, infrastructure failure began, and 3) understanding how this failure and its impacts on water resources have progressed over time. The primary project activities comprise using naturally-occurring chemical tracers in stream water and trees to reconstruct a history of water quality, and using historical data to reconstruct a history of infrastructure development. We expect our approach will be transferrable to other urban systems with aging infrastructure. Most broadly, this project will leverage our network of stakeholders to help inform city-level planning efforts to implement resilient infrastructure while accommodating rapid expansion of urban populations in the 21st century. Results from this project will be incorporated across the sustainability curriculum at the University of Texas at Austin, which includes interdisciplinary degrees and 24 courses that emphasize field experiences and engage 800 students per year in on-campus environmental research along one of the proposed stream study sites, as well as geoscience graduate programs at UT Austin and the University of Arizona. Graduate and undergraduate student training will emphasize inclusion of underrepresented minorities.At the onset of infrastructure failure in each Austin watershed, municipal water was introduced by leakage into relatively pristine natural hydrologic systems. We hypothesize that the distinct chemical compositions of these anthropogenic water sources were recorded in bald cypress trees at the onset of failure and in subsequent years as failure progressed. This project comprises a novel application of natural isotopic tracers to examine the impacts of urbanization on natural hydrology and stream ecology in three watersheds in the same hydrogeologic terrain. The primary variable among the watersheds is the extent of urbanization. We will analyze elemental, and Sr isotope variations in stream water, and develop methods for high resolution measurements of the Sr isotopes in the growth rings of bald cypress trees growing adjacent to those streams. We posit that the growth rate and isotopic composition of the tree rings encode a hydrologic history of the progressive failure of infrastructure. We will apply these data using hydrogeochemical models to: 1) trace the evolution of municipal water during its transmission through the natural hydrologic cycle in anthropogenically compromised watersheds; and 2) use dendrochemical variations to reconstruct decadally-resolved temporal changes in municipal water input to streams. These results will be used to identify, for the first time, both the timing of the onset of infrastructure failure and temporal changes in the magnitude and impacts of the failure. We will compare this temporal record of municipal water input with the history of urban development in the same watersheds to determine the threshold for the extent of urbanization, above which hydrologic and ecological impacts of failing infrastructure are manifested. This award is co-funded by the Hydrologic Sciences, Environmental Sustainability, and Environmental Engineering programs.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.