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的皮埃蒙特地区浅层地下水和溪流之间的关系，以及地质上类似的景观。这项工作包括在马里兰州皮埃蒙特地区的一组研究流域进行水样取样和地下观测，这将使用PI开发的新理论工具进行分析和建模。研究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，因为农业肥料的使用已经在地下水储存中产生了硝酸盐的遗产。同样，这些结果可能会影响我们对长期气候变化对水通过风化基岩运动的影响的理解，这对我们对地球的理解也有影响。地质时间尺度上的碳循环。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实地夏令营的STEM内容，并为巴尔的摩市中心学校的小学生提供参加夏令营的机会，这些学校主要是非洲裔美国人。将开发实践实验和实地水文资源，以丰富约翰霍普金斯大学的本科水文课程。将开发开放获取的虚拟讲习班、数据集和相关软件工具，以培训其他机构的研究生掌握新方法及其在实地站点的潜在应用。越来越多的研究表明，源流是由地下明显大量的水的周转而来的。然而，这种储存及其周转的性质，在集水区尺度上还没有得到很好的理解。与此同时，对关键区域的研究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压裂过程。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带的演变结构联系起来。一种新的理论方法，建立在时变传输时间分布的最新进展之上，现在允许在一个统一的函数f_Q中捕获存储，放电和年龄结构之间的新兴山坡尺度关系。这为表达临界带结构、气候变率和水文运输之间关系的基本假设提供了一个框架。假设将在马里兰州一个风化严重、断裂的分水岭的嵌套现场进行测试，在那里，地球物理研究表明，地形诱发的基岩压裂驱动了关键区域的结构。将进行被动同位素示踪取样、深、浅钻井、钻孔地球物理观测和灌溉试验相结合，以检查临界带结构，测试关于f_Q性质的定量假设，并检查该框架作为流域尺度耦合流动和运输建模基础的潜力。

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.