Monitoring the generation and transformation of subsurface stormflow from hillslopes through the riparian zone

监测从山坡穿过河岸带的地下风暴流的产生和转变

• 批准号: 493884652
• 负责人: Dr. Theresa Blume
• 金额: --
• 依托单位: Helmholtz-Zentrum Potsdam - Deutsches GeoForschungsZentrum (GFZ)
• 依托单位国家: 德国
• 项目类别: Research Units
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/493884652?language=en
• 关键词: Monitoring; generation; transformation; subsurface; stormflow

Project D aims at better understanding the generation of subsurface stormflow (SSF) on hillslopes, the associated thresholds and controls, and to what extent the hillslope SSF physical and chemical signals are modified on the passage through the riparian zone. We intend to reduce the elusiveness of SSF as a streamflow generation process across topographical, climatic and land use gradients. The SSF signal, although most often generated on the hillslopes, is likely to become transformed on its path from the footslope through the riparian zone into the stream. This is problematic for SSF research as the most common experimental methods focus either on the hillslopes (observing shallow groundwater table fluctuations and/or subsurface flow in trenches) or on the SSF solute tracer signal identified on the hillslope and then measured in the stream. The transformation of the SSF signal can include time delays, changes in flow path direction and in the magnitude of flow. These physical effects mostly increase the residence time in the riparian zone and may thus lead to a chemical transformation of the SSF signal by mixing and/or biogeochemical reactions. By the time it reaches the stream, the original SSF signal might be heavily modified and hard to identify. Ultimately, the spatio-temporal variability of hillslope-stream connectivity will govern how and when hillslope SSF affects streamflow. To evaluate the relevance of hillslope SSF for streamflow quantity, timing and quality, Project D will address the following research questions:(1) What are the thresholds and dynamics of SSF generated on the hillslopes?(2) Are there SSF-specific tracers or combinations of tracers that could be used to identify hillslope SSF in streamflow? How site specific are these signatures?(3) How is the hillslope SSF physical and chemical signal transformed in the riparian zone and does this change seasonally or with catchment wetness state?(4) What are the major controls in time and space for SSF generation, as well as riparian zone transformation?We will tackle the challenges described above with an innovative multi-site experimental approach. This approach includes the development of a dual-use trench, allowing us to measure SSF outflow signals (quantity, timing, and natural tracers) at the upslope side of the trench, while at the same time serving as an injection site for artificial tracers at the downslope side of the trench. An array of piezometers installed downslope of the trench for water level observation and sampling will make it possible to trace the flowpaths from the footslope across the riparian zone to the stream. We will install three trenches in each of our four test catchments. In a next step, we can identify flow path directions, mixing with riparian zone groundwater and the extent of transformation of the chemical signal in the riparian zone. Based on this, we will be able to identify SSF-specific tracers across a range of landscape configurations.

项目D旨在更好地了解山坡地下暴雨流（SSF）的产生，相关的阈值和控制，以及山坡SSF物理和化学信号在通过河岸带时的变化程度。我们打算减少SSF的难以捉摸的地形，气候和土地利用梯度的径流生成过程。SSF信号虽然通常在山坡上产生，但很可能在其从山麓经过河岸带进入溪流的路径上发生变化。这是SSF研究的问题，因为最常见的实验方法集中在山坡上（观察浅层地下水位波动和/或沟渠中的地下水流）或SSF溶质示踪剂信号确定的山坡上，然后在流中测量。SSF信号的变换可以包括时间延迟、流动路径方向和流量大小的变化。这些物理效应主要增加了在河岸带的停留时间，因此可能导致SSF信号通过混合和/或非地球化学反应的化学转化。当它到达流时，原始SSF信号可能被严重修改并且难以识别。最终，时空变化的山坡流连接将决定如何以及何时山坡SSF影响径流。为评估山坡SSF与径流量、时间和质量的相关性，项目D将解决以下研究问题：（1）山坡SSF产生的阈值和动态是什么？(2)是否有特定的SSF示踪剂或示踪剂的组合，可用于识别坡面SSF在径流？这些签名有多具体？(3)山坡SSF的物理和化学信号在河岸带是如何转换的？这种转换是随季节变化还是随流域湿度变化？(4)SSF的产生和河岸带的变化在时间和空间上的主要控制因素是什么？我们将通过创新的多站点实验方法应对上述挑战。这种方法包括开发一个双重用途的沟槽，使我们能够在沟槽的上坡侧测量SSF流出信号（数量，时间和自然示踪剂），同时作为人工示踪剂在沟槽的下坡侧的注入点。在沟渠的下坡处安装了一组测压计，用于水位观测和取样，这将使追踪从坡脚穿过河岸带到河流的水流路径成为可能。我们将在四个测试集水区中的每个集水区安装三条沟渠。在下一步中，我们可以确定流动路径方向，与河岸带地下水的混合以及河岸带化学信号的转化程度。基于此，我们将能够在一系列景观配置中识别SSF特定的示踪剂。