What are the seasonal controls on stream-riparian groundwater exchange during baseflow recession in headwater catchments?

该奖项是根据2009年美国复苏和再投资法案（公法111-5）资助的。“潜流区和河岸区在流域尺度的营养物质、热量和能量收支中发挥着重要作用。重要的研究已经进行了地下水和河岸带的地球化学和水文功能，虽然往往是彼此孤立的。在这里，我们试图确定动态谷底水文是如何控制山谷形态和梯度，这反过来又如何影响整个夏季基流衰退在源头流域的潜流交换。我们提出了以下研究问题：1）地下水流的下谷和跨谷矢量如何通过季节性基流衰退而变化？2)这些变化是如何被山谷尺度的形态和梯度所控制的？3)下谷和跨谷矢量的模式在空间上有多一致？4)在季节性基流衰退期间，潜流交换的程度如何变化？我们将解决这些问题相结合的领域的方法，地下水流和运输建模，流溶质运移建模，并综合分析示踪剂数据和地球物理调查流示踪剂分布在地下。这项研究将显着提高我们的能力，预测和量化的水文河流地下水交换。我们建议在页岩山临界区观测站举办一次研讨会，汇集水文学家和水文学家，以确定河流-地下水相互作用中水文物理学的前沿和未来方向。此外，我们还将培训两名研究生和两名本科生水文学，地下水建模，水物理学和溶质运移。我们将积极从代表性不足的申请人中招募到宾夕法尼亚州立大学。

ABSTRACT"This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5)."Hyporheic zones and riparian zones play important roles in catchment-scale budgets of nutrients, heat, and energy. Significant research has been conducted on the biogeochemical and hydrologic functions of both hyporheic and riparian zones, though often in isolation from each other. Here, we seek to determine how dynamic valley-bottom hydrology is controlled by valley morphology and gradient, and how this in turn influences hyporheic exchange throughout summer baseflow recession in headwater catchments. We pose the following research questions:1) How do down-valley and cross-valley vectors of subsurface flow change through seasonal baseflow recession?2) How are these changes controlled by valley-scale morphology and gradient?3) How spatially consistent are the patterns of down- and cross-valley vectors? 4) How does the extent of hyporheic exchange change during seasonal baseflow recession? We will address these questions by combining field methods, groundwater flow and transport modeling, stream solute transport modeling, and integrated analyses of tracer data and geophysical surveys of stream tracer distribution in the subsurface. This research will significantly enhance our ability to predict and quantify the hydrology of stream-groundwater exchange. We propose to conduct a workshop at the Shale Hills Critical Zone Observatory to bring together hydrologists and geophysicists to define the cutting edge and future directions of hydrogeophysics in stream-groundwater interactions. We will additionally train two graduate students and two undergraduate students in hydrology, groundwater modeling, geophysics, and solute transport. We will actively recruit from under-represented applicants to Penn State.