Collaborative research: Linking scales of geomorphology and solute transport in river corridors

PI：Aaron Packman（西北大学）、Douglas Jerolmack（宾夕法尼亚大学）、Jud Harvey（美国地质调查局）概述：河流中的溶质迁移是一个受水文和地貌动力学影响的复杂问题。为了改进对河流系统中长期平均生物地球化学处理速率的评估，能够预测水文动力学、地貌动力学和溶质迁移的相互作用非常重要。溪流-地下水文相互作用受到表面形态的调节，强烈影响溪流和孔隙水中的溶质输运，从而控制非常广泛的生物地球化学过程。在这里，我们建议获得一个独特的新数据集，其中包括对经常发生高流量和沉积物输送事件的沙床河中的河流形态动力学和溶质输送的观察。我们还建议开发新的理论，以便将先前在地貌和地表-地下水相互作用中观察到的比例关系纳入河流中长期平均溶质迁移的模型中。该模型将通过结合溪流流量变化和河道形态的观测统计数据应用于研究现场，并将使用对溶质渗透到地下的直接观察和在一定时间尺度内平均的净下游溶质迁移进行测试。 智力价值：这项工作的智力价值在于促进对溪流水文学、河流形态动力学、地表-地下水相互作用和河流中溶质迁移之间联系的基本理解。这是一个极其复杂的问题，因为它不仅涉及湍流边界相互作用，还涉及高度非均质的近河环境中的沉积物输送和孔隙流体流动。在这里，我们将综合水文学和地貌学领域的许多最新观察结果和假设，以确定河流中的流动动力学和形态动力学之间的联系如何控制不同空间和时间尺度上的溶质迁移。虽然现在人们普遍认识到需要进行这种综合，以便以综合的方式评估环境系统的行为，但这种综合在实践中很少实现。通过开发利用地貌和水文尺度关系中的共性的新理论，我们能够对控制河流廊道各种空间和时间尺度上的溶质输运动态的综合过程进行明确的评估。更广泛的影响：所提出的努力将对环境科学以及水资源和水生生态系统的相关管理做出非常广泛的贡献。此外，通过各种协同活动，我们还将在人力资源开发和整个科学界产生许多更广泛的影响。该项目的结果将为评估河流系统中各种重要溶质的迁移提供重要的、必要的能力。迫切需要可用于预测形态变化（例如土地利用变化）和可变水文强迫（自然流量变化和替代气候变化情景）下的长期平均运输行为之间联系的工具。因此，预计该项目的结果不仅有助于详细了解河流动态，而且还将在支持河流系统中碳、营养物、污染物和一系列其他重要物质的迁移和处理分析方面产生非常广泛的影响。从本质上讲，该项目的努力为以科学为基础的淡水资源可持续管理迈出了关键一步。我们将通过支持更广泛的科学界致力于解决这些问题，进一步加强这些一般性贡献。我们将存档我们将获得的独特现场数据集，并将其公开提供给其他理论家和建模者，以促进更广泛的河流廊道流动和运输模型的开发和测试。我们还将通过在主要技术会议上召开多次定向跨学科会议，以及将项目成果直接转化为目前由 NSF 赞助的更广泛的水文综合活动，促进科学讨论，特别是科学成果的综合，以解决政策和管理问题。最后，我们将通过这项工作培训众多年轻研究者，参与协同和协作的国际活动，并利用项目成果进一步推动我们不断努力，鼓励大学预科学生，特别是来自代表性不足的少数族裔的学生进入科学领域，从而为人力资源开发做出广泛的贡献。

PIs: Aaron Packman (Northwestern University), Douglas Jerolmack (University of Pennsylvania), Jud Harvey (U.S. Geological Survey)Overview: Solute transport in rivers is a complex problem influenced by both hydrologic and geomorphic dynamics. It is important to be able to predict the interactions of hydrologic dynamics, geomorphic dynamics, and solute transport in order to improve assessment of long-term average biogeochemical processing rates in river systems. Stream-subsurface hydrologic interactions are modulated by surface morphology and strongly affect solute transport in both streams and pore waters, thereby controlling a very wide range of biogeochemical processes. Here we propose to obtain a unique new data set encompassing observations of both fluvial morphodynamics and solute transport in a sand-bed river subject to frequent high-flow and sediment-transport events. We also propose to develop new theory to allow scaling relationships previously observed in both geomorphology and surface-groundwater interactions to be incorporated into a model for long-term average solute transport in rivers. The model will be applied to the study site by incorporating observed statistics of stream flow variations and channel morphology, and will be tested using direct observations of both solute penetration into the subsurface and net downstream solute transport averaged over a range of time scales.Intellectual Merit: The intellectual merit of this work lies in advancing fundamental understanding of the linkage between stream hydrology, fluvial morphodynamics, surface-groundwater interactions, and solute transport in rivers. This is an exceedingly complex problem as it involves not only turbulent flow-boundary interactions, but also sediment transport and pore fluid flow in the highly heterogeneous near-stream environment. Here we will synthesize numerous recent observations and hypotheses developed separately in hydrology and geomorphology in order to ascertain how the linkage between flow dynamics and morphodynamics in rivers controls solute transport over various spatial and temporal scales. While it is now generally recognized that such synthesis needs to be done in order to assess the behavior of environmental systems in an integrated fashion, such integration has rarely been achieved in practice. By developing new theory that takes advantage of commonality in geomorphic and hydrologic scaling relationships, we enable explicit evaluation of the integrated process that control solute transport dynamics over a variety of spatial and temporal scales in river corridors.Broader Impacts: The proposed effort will contribute very broadly to environmental science and the associated management of water resources and aquatic ecosystems. Further, through a variety of synergistic activities we will also realize numerous broader impacts in human resource development and in the scientific community at large. The project results will provide significant, necessary capability to evaluate the migration of a wide range of important solutes in river systems. There is a critical need for tools that can be used to predict the linkage of morphological variations (e.g., land-use changes) and long-term average transport behavior under variable hydrologic forcing (natural flow variability and alternative climate change scenarios). Therefore the project results can be expected to not only contribute detailed understanding of river dynamics, but also to have very broad impacts in supporting analysis of the migration and processing of carbon, nutrients, contaminants, and a range of other important substances in river systems. Essentially, the project efforts provide a critical step towards scientifically based sustainable management of freshwater resources. We will further enhance these general contributions by supporting the broader scientific community working on these problems. We will archive the unique field data set that we will acquire, and make it publicly available to other theoreticians and modelers to facilitate broader development and testing of models for flow and transport in river corridors. We will also facilitate scientific discourse, and particularly synthesis of scientific results to address policy and management questions, by convening multiple, directed interdisciplinary sessions at major technical conferences, and by translating project results directly into the broader Hydrologic Synthesis activity currently sponsored by NSF. Finally, we will realize broad contributions to human resource development by training numerous young investigators through this work, by engaging in synergistic and collaborative international activity, and by using project results to further our ongoing efforts to encourage pre-college students, and particularly students from under-represented minorities, to enter careers in science