Effects of Successive Peak Flow Events on Hyporheic Exchange and Residence Times
Effects of Successive Peak Flow Events on Hyporheic Exchange and Residence Times
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DOI：
10.1029/2020wr027113
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发表时间：
2020-07
影响因子：
5.4
通讯作者：
Tanu Singh;J. Gomez‐Velez;Liwen Wu;A. Wörman;D. Hannah;S. Krause
中科院分区：
文献类型：
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作者：
Tanu Singh;J. Gomez‐Velez;Liwen Wu;A. Wörman;D. Hannah;S. Krause
潮汐交换是对河床生物地球化学过程的类型和速率的重要控制，包括新陈代谢、呼吸作用、养分周转和污染物的转化。以前的工作表明，在单个高峰流量事件期间增加流量，通过加强水和溶解溶质的交换，加强了生物地球化学周转。然而，由于交换过程的非稳定性质，连续的峰值流动事件并不表现出停留时间和周转的成比例变化，在某些情况下，可能会降低潜流带的生物地球化学势。在这里，我们使用一个基于过程的模型来探索连续的峰值流量事件对床型诱导的低渗交换的流动和运输特性的作用。我们系统地分析了事件的强度、持续时间和峰间时间对潜流带通量、穿透和停留时间的影响。通过对一种保守溶质的输运模拟，推断了各事件对沉积物-水界面溶质输运的相对贡献。除了低速流场中的时间变化外，我们的结果还表明，两个事件之间的分离决定了滞留时间的时间演变，并且事件时间滞后于系统的记忆导致可以独立处理的连续事件。这项研究强调了流量变化在潮汐交换动力学中的重要性，以及它对河流走廊污染物的生物地球化学转化和归宿的潜在影响。
Hyporheic exchange is a crucial control of the type and rates of streambed biogeochemical processes, including metabolism, respiration, nutrient turnover, and the transformation of pollutants. Previous work has shown that increasing discharge during an individual peak flow event strengthens biogeochemical turnover by enhancing the exchange of water and dissolved solutes. However, due to the nonsteady nature of the exchange process, successive peak flow events do not exhibit proportional variations in residence time and turnover, and in some cases, can reduce the hyporheic zones' biogeochemical potential. Here, we used a process‐based model to explore the role of successive peak flow events on the flow and transport characteristics of bedform‐induced hyporheic exchange. We conducted a systematic analysis of the impacts of the events' magnitude, duration, and time between peaks in the hyporheic zone's fluxes, penetration, and residence times. The relative contribution of each event to the transport of solutes across the sediment‐water interface was inferred from transport simulations of a conservative solute. In addition to temporal variations in the hyporheic flow field, our results demonstrate that the separation between two events determines the temporal evolution of residence time and that event time lags longer than the memory of the system result in successive events that can be treated independently. This study highlights the importance of discharge variability in the dynamics of hyporheic exchange and its potential implications for biogeochemical transformations and fate of contaminants along river corridors.