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首页> 外文期刊>Water resources research >Hyporheic exchange in gravel bed rivers with pool-riffle morphology: Laboratory experiments and three-dimensional modeling
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Hyporheic exchange in gravel bed rivers with pool-riffle morphology: Laboratory experiments and three-dimensional modeling

机译：池-沟形态的砾石床河流中的疏水交换：室内实验和三维建模

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摘要

We report the first laboratory simulations of hyporheic exchange in gravel pool-riffle channels, which are characterized by coarse sediment, steep slopes, and three-dimensional bed forms that strongly influence surface flow. These channels are particularly important habitat for salmonids, many of which are currently at risk worldwide and which incubate their offspring within the hyporheic zone. Here we perform a set of laboratory experiments examining the effects of discharge and bed form amplitude on hyporheic exchange, with surface-subsurface mixing measured directly from the concentration decay of a conservative tracer (fluorescein) injected into the surface flow. Near-bed pressure measurements were also used to predict hyporheic exchange from a three-dimensional pumping transport model. Comparison of the predicted and observed hypqrheic exchange shows good agreement, indicating that the major mechanism for exchange is bed form-induced advection. However, the effect of bed forms is modulated by discharge and the degree of topographic submergence. We also tested the performance of the hydrostatic pressure as a proxy for the observed near-bed pressure in driving hyporheic exchange, which would facilitate field measurement and analysis of hyporheic flow in natural rivers. We found agreement with measured hyporheic exchange only for low bed form amplitudes and high flows.
机译：我们报告了砾石池-浅滩通道水流交换的第一个实验室模拟，其特征是粗沙，陡峭的坡度和强烈影响地表水流的三维河床形式。这些通道是鲑鱼特别重要的栖息地，鲑鱼目前在世界范围内处于危险之中，并在低潮区内孵化其后代。在这里，我们进行了一组实验室实验，研究了流量和床层振幅对流变交换的影响，其中表面下混合是直接从注入表面流中的守恒示踪剂（荧光素）的浓度衰减直接测量的。近床压力测量也被用于从三维泵送运输模型预测流变交换。预测的和观察到的交换性交换的比较显示出很好的一致性，表明交换的主要机制是床形式引起的对流。但是，河床形式的影响受流量和地形淹没程度的影响。我们还测试了静水压力的性能，以代替在驱动低渗交换时观察到的近床层压力，这将有助于现场测量和分析天然河流中的低渗流量。我们发现仅对于低床形振幅和高流量，与测量的水交换交换相一致。

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