<br>水热交换对蜿蜒弯曲驱动的低流区洪水和局部风暴事件的响应,Science of the Total Environment

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水热交换对蜿蜒弯曲驱动的低流区洪水和局部风暴事件的响应
Science of the Total Environment ( IF 8.2 ) Pub Date : 2023-04-26 , DOI: 10.1016/j.scitotenv.2023.163732
Jiawei Ren ₁ , Haizhu Hu ₂ , Xixi Lu ₃ , Ruihong Yu ₂

Affiliation

低流区，即河流/河岸生态系统中的地下水-地表水界面，在流域尺度的水输送、能量流动和生物地球化学循环中起着关键作用。水和热交换是调节低流区生物地球化学循环的基本过程。为了更好地了解蜿蜒溪流中的流动和热传递，在夏季洪水季节进行了水位和温度的高分辨率测量，并结合了蜿蜒弯道区流动和热传递的 3-D 耦合模型。结果显示低流水和热交换的明显时空变化。洪水事件（上游降雨产生的洪水流入）和局部暴雨事件（发生在局部研究区域上的暴风雨或降雨）是耦合过程的主要驱动因素。来自上游的洪水增加了河床和内岸的低流水和热交换，导致河道内停留时间延长，并由于降雨后的热恢复而使河床和河岸变暖。局部暴雨事件在横向和垂直方向上增加了低流水和热交换通量，并使河床和河岸降温。蜿蜒曲折中的水交换和热力状态似乎更多地由局部交换流驱动，而外岸的对应物则由区域地下水流主导。内岸的温度比外岸高 1 至 3 °C，表明蜿蜒内河水和地下水之间的水文连通性更好。蜿蜒的顶端是低流水和热交换的热点。结果突出了蜿蜒系统中河流形态、低流流和热非均质性之间的紧密耦合。

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Water and heat exchange responses to flooding and local storm events in the hyporheic zone driven by a meandering bend

The hyporheic zone, i.e. the groundwater-surface water interface within riverine/riparian ecosystems, plays a key role in water transport, energy flow and biogeochemical cycling at watershed scales. Water and heat exchange are fundamental processes regulating biogeochemical cycles in the hyporheic zones. To improve the understanding of hyporheic flow and heat transport in meandering streams, high-resolution measurements of water level and temperature, combined with a 3-D coupled model of flow and heat transport in the hyporheic zone of a meandering bend, were carried out during a summer flood season. Results show the distinct spatio-temporal variations of hyporheic water and heat exchange. Flooding events (the incoming flood water generated by the upstream rainfall) and local rainstorm events (the storm or rainfall occurring over the local study area) are major drivers for the coupled processes. Incoming flooding from the upper stream increases the hyporheic water and heat exchange in the riverbed and inner bank leading to the longer intra-meander residence times, and warms the riverbed and riverbanks due to the post-rainfall thermal recovery. Local rainstorm event increases hyporheic water and heat exchange flux both laterally and vertically and cools down the riverbed and riverbanks. The water exchange and thermal regimes in the intra-meander seems more driven by the local exchange flows, while the counterparts in the outer bank are dominated by the regional groundwater flow. The temperatures in the inner banks are 1 to 3 °C higher than those in the outer banks, indicating the better hydrological connectivity between river water and groundwater in the intra-meander. The meander apex is a hot spot for hyporheic water and heat exchange. The results highlight the close coupling among river morphology, hyporheic flow, and thermal heterogeneity in a meander system.

更新日期：2023-04-26

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