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

摘要：“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。”潜流带和河岸带在流域尺度的养分、热量和能量收支中起着重要作用。虽然通常是相互孤立的，但对暗河带和河岸带的生物地球化学和水文功能进行了大量研究。在这里，我们试图确定动态山谷底部水文是如何由山谷形态和梯度控制的，以及这反过来又是如何影响源头集水区夏季基流衰退期间的潜流交换的。我们提出了以下研究问题：1)在季节基流衰退过程中，地下水流的下行和跨谷矢量是如何变化的？2)这些变化是如何受到山谷尺度形态和梯度的控制的？3)向下和跨谷矢量的模式在空间上的一致性如何？4)在季节性基流衰退期间，隐性交换的程度如何变化？我们将通过结合现场方法、地下水流动和运输模型、河流溶质运输模型以及对示踪剂数据和地下河流示踪剂分布的地球物理调查的综合分析来解决这些问题。该研究将大大提高我们预测和量化河流-地下水交换水文的能力。我们建议在页岩山临界带观测站举办一个研讨会，汇集水文学家和地球物理学家，以确定河流-地下水相互作用中水文地球物理学的前沿和未来方向。我们将在水文学、地下水模拟、地球物理学和溶质运移方面培养两名研究生和两名本科生。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.