CAREER: proposal to link catchment hydrologic transport to the evolved architecture of the critical zone

这项研究旨在更好地了解美国大西洋中部山前浅层地下水和径流之间的关系，以及地质上相似的景观。这项工作涉及马里兰州皮埃蒙特地区一组研究流域的水样和地下观测相结合，这些数据将用于使用PI开发的新理论工具进行分析和建模。这些结果将有助于联合研究工作，以了解气候变化对水质的影响，在这些地方，农业化肥的使用在地下水储存中产生了遗留的硝酸盐。同样，这一结果可能有助于我们理解长期气候变化对水在风化基岩中运动的影响，这对于我们理解地球？S在地质时间尺度上的碳循环具有重要意义。研究和教育以多种方式融入这项工作。该项目的一部分资金将用于丰富外地日间夏令营的STEM内容，并为巴尔的摩市中心以非裔美国人为主的学校的小学生提供进入夏令营的机会。将开发动手实验和实地水文学资源，以丰富约翰霍普金斯大学的本科生水文学课程。将开发开放式虚拟讲习班、数据集和相关软件工具，对其他机构的研究生进行新方法的培训，并将其应用于其外地地点。越来越多的研究表明，水源流向来自地下水中明显大量的水的周转。然而，在集水规模上，这种储存及其周转的性质并没有得到很好的理解。与此同时，对临界区的调查正在阐明对地下结构和性质的控制，包括产生充满水的孔隙体积的风化和破裂过程。该项目旨在将山坡和次流域的紧急储存和运输特性与整个地下临界区的演变结构联系起来。一种新的理论方法建立在时变渡越时间分布的最新进展基础上，现在允许在单一的统一函数f_q中捕捉出现的山坡尺度的蓄水、流量和年龄结构之间的关系，这为表达关于临界带结构、气候变异性和水文输送之间的关系的基本假设提供了一个框架。假说将在马里兰州一个深度风化、破裂的分水岭的嵌套现场进行验证，那里的地球物理研究表明，地形诱导的基岩破裂驱动着临界区的结构。将结合被动同位素示踪采样、深浅钻探、钻孔地球物理观测和灌溉实验来检验临界区结构，检验关于fq性质的定量假说，并检验该框架作为流域-尺度耦合流动和输送模拟的基础的潜力。

This research aims to better understand the relationship between shallow groundwater and streamflow in the Piedmont of the mid-Atlantic US, and geologically similar landscapes. The work involves a combination of water sampling and subsurface observations in a set of study watersheds in the Maryland Piedmont region, which will feed into analysis and modeling using novel theoretical tools developed by the PI. The results will contribute to allied research efforts to understand the effects of climate variability on water quality where agricultural fertilizer use has generated a legacy of nitrate in groundwater stores. Similarly the results may have implications for our understanding of the effects of long-term climate variability on the movement of water through the weathering bedrock, which has implications for our understanding of the earth?s carbon cycle on geologic timescales. Research and education are integrated into this work in multiple ways. A portion of the funds from the project will be used to enrich the STEM content of summer day camps at the field site, and provide access to the camps for elementary school children from predominantly-African American inner-city Baltimore schools. Hands-on experimental and field hydrology resources will be developed to enrich the undergraduate hydrology curriculum at Johns Hopkins. Open-access virtual workshops, datasets and associated software tools will be developed to train graduate students at other institutions in new methodologies and their potential applications to their field sites.An increasing number of studies suggest that headwater streamflow is derived from the turnover of apparently large volumes of water in the subsurface. However this storage, and the nature of its turnover, is not well understood at the catchment scale. At the same time, investigations into the critical zone are elucidating controls on the structure and properties of the subsurface, including the processes of weathering and fracturing that generate water-filled pore volume. This project aims to link the emergent storage and transport properties of hillslopes and sub-watersheds to the evolved structure of the entire subsurface critical zone. A novel theoretical approach, built on recent advances in time-variable transit time distributions, now allows emergent hillslope-scale relationships between storage, discharge, and age structure to be captured in a single unified function, f_Q. This provides a framework for expressing fundamental hypotheses about the relationship between critical zone structure, climate variability, and hydrologic transport. Hypotheses will be tested in nested field sites in a deeply weathered, fractured watershed in Maryland, where geophysical studies suggest that topographically-induced bedrock fracturing drives the structure of the critical zone. A combination of passive isotope tracer sampling, deep and shallow drilling, borehole geophysical observations and irrigation experiments will be conducted to examine the critical zone structure, test quantitative hypotheses about the nature of f_Q, and examine the potential of this framework as a basis for catchment-scale coupled flow and transport modeling.