Collaborative Research: Geophysical characterization of a karst aquifer using dynamic recharge events

合作研究：利用动态补给事件对岩溶含水层进行地球物理表征

• 批准号: 1740526
• 负责人: Andrew Luhmann
• 金额: $ 48.05万
• 依托单位: New Mexico Institute of Mining and Technology
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2018
• 资助国家: 美国
• 起止时间: 2018-04-01 至 2018-10-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1740526&HistoricalAwards=false
• 关键词: Collaborative; Research; Geophysical; characterization; karst

Karst aquifers are important water resources, providing water for up to a quarter of the world?s population. These aquifers are complex hydrogeologic systems, where flow and transport predominantly occur through preferential flow paths or conduits that range in size from cm-scale openings to passages much larger than required for human access (caves). Despite their hydrologic importance, the location of karst conduits and characteristics of the larger aquifer are typically poorly constrained. To address these problems, we will monitor recharge-induced responses that arise as water flows into the subsurface in a karst aquifer in Florida using geophysical instrumentation to characterize the conduits, subsurface flow, and the larger karst system. The noninvasive remote sensing investigation will generate knowledge for direct societal benefit, including tools to improve the creation of karst hazards maps that highlight areas susceptible to sinkhole formation, the identification of preferential flow paths relevant to contaminant transport, and the development of a methodology to determine subsurface flow for water supply considerations. We will develop a temporary, interactive traveling exhibit in collaboration with the National Cave and Karst Research Institute that will frequent visitor centers near the field site in Florida and in New Mexico to increase public engagement and scientific literacy about karst hydrogeology and environmental seismology. The project will also contribute to the education of the next generation of the scientific workforce through the involvement of two graduate students at New Mexico Tech, an undergraduate student at the University of Florida, two undergraduate student interns through the IRIS undergraduate student intern program, and two early career scientists and a mid-career female scientist in an EPSCoR state. Finally, collected datasets will be incorporated into lecture material and homework sets of undergraduate and graduate courses at New Mexico Tech, which is a Hispanic-serving institution.A previous pilot study demonstrated the generation of seismic signals during artificial recharge experiments and a natural recharge event in a karst aquifer. These and other geophysical signals are caused by processes during flow through karst aquifers and includes pressure pulses generated as recharge enters conduits with full pipe flow, pore pressure changes in fractures and the rock matrix, mass loading induced subsidence due to changes in water mass, and turbulent interaction of flow with the wall rocks. To capitalize on the information content provided by these signals, we will use simultaneous, large-scale observations of recharge events at two co-located geophysical sensor networks to characterize the conduit network, flow processes within this network, and material properties of the larger karst system. Seismometers, tiltmeters, and other instruments will be deployed at the Santa Fe River Sink-Rise system in Florida to observe karst recharge events over a two-year period. This field site has a well-constrained conduit network, and thus it permits verification of the interpreted geophysical signals that arise from hydrologic processes. This transformative project will not only enable delineation of the karst conduit network, but will do so while providing a regionally integrated analysis of the karst aquifer flow system based on deformation observations on the timescales between fractions of a second to months. As recharge activates new flow paths, geophysical monitoring enables extensive 3D characterization of the dynamics and evolution of flow during recharge-induced changes in the aquifer. Furthermore, the signals will help to determine the architecture in the subsurface between the conduits and the surface, advancing knowledge of critical zone environments, for example, by specifically determining soil and regolith thicknesses and depths to the soil-rock interface. The young field of environmental seismology encompasses studies of a range of Earth surface processes, and this project will use and expand the respective methods to transform the understanding of karst aquifers across the full frequency range of deformation and develop techniques in preparation for a future karst critical zone observatory.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.

岩溶含水层是重要的水资源，为世界上四分之一的人口提供水源。这些含水层是复杂的水文地质系统，其中的流动和运输主要通过优先流动路径或管道发生，这些路径或管道的尺寸范围从厘米级开口到比人类进入所需的通道（洞穴）大得多的通道。尽管具有水文重要性，但岩溶管道的位置和较大含水层的特征通常很少受到限制。为了解决这些问题，我们将使用地球物理仪器监测水流入佛罗里达州岩溶含水层地下时引起的补给响应，以表征管道、地下水流和更大的岩溶系统。非侵入性遥感调查将产生直接社会效益的知识，包括改进喀斯特灾害地图创建的工具，突出显示容易形成天坑的区域，确定与污染物输送相关的优先流动路径，以及开发确定方法出于供水考虑的地下水流。我们将与国家洞穴和喀斯特研究所合作开发一个临时的互动旅游展览，该展览将经常出现在佛罗里达州和新墨西哥州现场附近的游客中心，以提高公众对喀斯特水文地质学和环境地震学的参与度和科学素养。该项目还将通过新墨西哥理工学院的两名研究生、佛罗里达大学的一名本科生、通过 IRIS 本科生实习计划的两名本科生实习生的参与，为下一代科学劳动力的教育做出贡献。 EPSCoR 州的两名早期职业科学家和一名职业中期女科学家。最后，收集的数据集将被纳入新墨西哥理工学院（新墨西哥理工学院）本科生和研究生课程的讲座材料和作业中，该学院是一所为西班牙裔服务的机构。之前的一项试点研究演示了在人工补给实验和自然补给事件期间地震信号的生成在喀斯特含水层中。这些和其他地球物理信号是由流经岩溶含水层期间的过程引起的，包括补给进入全管流管道时产生的压力脉冲、裂缝和岩石基质中的孔隙压力变化、由于水质量变化引起的质量负载引起的沉降，以及水流与围岩的湍流相互作用。为了利用这些信号提供的信息内容，我们将使用两个位于同一地点的地球物理传感器网络的同步、大规模的补给事件观测来表征管道网络、该网络内的流动过程以及较大岩溶的材料特性系统。地震仪、倾斜仪和其他仪器将部署在佛罗里达州圣达菲河沉升系统中，以观测两年内的喀斯特补给事件。该现场有一个约束良好的管道网络，因此可以验证由水文过程产生的解释的地球物理信号。这一变革性项目不仅能够描绘岩溶管道网络，而且还将根据几分之一秒到几个月的时间尺度的变形观测，对岩溶含水层流系统进行区域综合分析。随着补给激活新的水流路径，地球物理监测可以对补给引起的含水层变化期间的流动动力学和演化进行广泛的 3D 表征。此外，这些信号将有助于确定管道和地表之间的地下结构，从而增进对关键区域环境的了解，例如，通过专门确定土壤和风化层的厚度以及土壤-岩石界面的深度。环境地震学这一新兴领域涵盖了一系列地球表面过程的研究，该项目将使用和扩展各自的方法来转变对整个变形频率范围内岩溶含水层的理解，并开发技术，为未来岩溶临界该奖项反映了 NSF 的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。