Urban "Karst": The Impacts of Utility/Service Conduits/Ducts on Urban Groundwater Systems

992899 SharpUrban地区在水文学上类似于岩溶环境--它们具有内部排水系统（雨水管）、暴雨后流动的地表溪流（铺设的排水沟）以及可能由裂缝、管道和洞穴（掩埋的公用事业沟渠、废弃管道等）主导的渗透性结构。 目前，世界上一半以上的人口生活在城市环境中。 预计这一数字的绝对值和百分比都将增加，城市地区的增长率高于城市人口的增长率。 最近的研究表明，城市化对浅层地下水的补给率和渗透率分布都有重大影响。 例如，尽管增加了“不透水”覆盖层，但水管和污水系统的渗漏仍会增加补给量！ 城市化影响到地下水污染和补救、水资源、河流流量和岩土工程。 地下公用事业系统的建设和废弃在浅层地下形成了一个相互连接的网络，具有高度对比的渗透率（初步试验中可达7-10个数量级）。该项目将：（1）研究城市公用事业管线、管道、导管及其伴随的沟渠如何改变天然渗透结构;（2）比较碳酸盐岩、页岩/泥岩和冲积环境之间以及与未扰动环境之间的这些变化;（3）预测这些变化如何影响补给和城市地下水污染;以及（4）测试化学示踪剂（特别是硼）以验证模型并确定沟槽网络的影响。 我们将使用数值模型FAC 3DVS和实地研究来分析这些“途径”对地下水流和溶质运移的影响。 我们将预测，对于有代表性的情况下，如何沟渠网络的建设和水管和污水系统的泄漏对城市地下水系统的影响。 将测试几种示踪剂，以评估任何影响的程度。 这项研究是美国德克萨斯大学奥斯汀分校和英国伦敦大学皇家霍洛威学院的合资项目。 它将对比一个年轻和快速发展的城市[奥斯汀]和一个更成熟的城市环境[伦敦]的城市发展结果，在那里城市化的长期影响应该更加明显。 在英国的工作是一个单独的建议，英国研究理事会的主题。

992899SharpUrban areas are hydrologically similar to karstic settings-they have internal drainage (storm sewers), surface streams (paved drainage ditches) that flow after heavy rains, and a permeability structure that may be dominated by fractures, conduits, and caves (buried utility trenches, abandoned pipes, etc.). Over half the world's population now lives in the urban environment. This is projected to increase both absolutely and as a percentage, and the urban area is increasing at a greater rate than the urban population. Recent studies on urbanization demonstrate signficant impacts on both the rates of recharge and permeability distributions within the shallow subsurface. For example, leakage from water mains and sewerage systems can increase recharge despite increases in "impervious" cover! Urbanization affects groundwater pollution and remediation, water resources, stream flows, and geotechnical projects. The construction and abandonment of subsurface utility systems create an interconnected network in the shallow subsurface with highly contrasting permeabilities (up to 7-10 orders of magnitude in preliminary tests).This project will: (1) examine how urban utility lines, ducts, conduits and their accompanying trenches alter natural permeability structure; (2) compare these changes between carbonate, shale/mudstone, and alluvial environments and with undisturbed settings; (3) predict how such changes affect recharge and urban groundwater contamination; and (4) test chemical tracers (specifically boron) to verify the models and identify the impact of trench networks. We will analyze the effects of these "pathways" on groundwater flow and solute transport using the numerical model FAC3DVS and field studies. We will predict, for representative scenarios, how the construction of trench networks and the leakage from water mains and sewage systems impact on urban groundwater systems. Several tracers will be tested to assess the magnitude of any effects. The research is a joint venture between The University of Texas at Austin, USA, and Royal Holloway College University of London, UK. It will contrast the outcome of urban development in a young and rapidly growing city [Austin] and a more mature urban environment [London] where the long-term effects of urbanization should be more apparent. The work in the UK is the subject of a separate proposal to the British Research Councils.