Sensitivity of Simulated Hyporheic Exchange to River Bathymetry: The Steinlach River Test Site
Sensitivity of Simulated Hyporheic Exchange to River Bathymetry: The Steinlach River Test Site
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模拟水流交换对河流测深的敏感性：斯坦拉赫河试验场
DOI：
10.1111/gwat.12816
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发表时间：
2018
期刊：
影响因子：
2.6
通讯作者：
W. Nowak
中科院分区：
文献类型：
--
作者：
R. Chow;Hao Wu;J. Bennett;Jürnjakob Dugge;T. Wöhling;W. Nowak
本研究确定了模拟次流交换时对预测偏差影响最大的河流测深方面。为了研究这个问题，我们建立了德国西南部施泰因拉赫河试验场的高度参数化的 HydroGeoSphere 模型作为参考。然后用更简单的测深方法对该模型进行修改，评估潜流交换通量和渡越时间分布的变化。结果表明，使用三维全耦合模型通过高分辨率详细水深测量模拟潜流交换会产生嵌套的多尺度潜流交换系统。解析不佳的水深测量会低估小规模的潜流交换，使模拟的潜流交换偏向更大的尺度，从而导致高估潜流交换停留时间。当推断流域内整条河流的所有曲流时，这可能会导致对流域减少污染物的能力的估计出现严重偏差。仅靠详细的河流坡度不足以准确模拟失去和获得河流河段的位置和程度。因此，需要河流内测深高低点的局部河床形态。通过优先考虑沿着蜿蜒河道的深海线和大根线进行测深测量，水深测量活动可以更加有效。我们将 gegenweg 定义为在平均流量条件下连接与 thalweg 相对的河流连续横截面中最浅点的线。结合当地的床形可能会捕捉潜流交换的嵌套性质，从而对潜流交换通量和传输时间进行更具物理意义的模拟。
This study determines the aspects of river bathymetry that have the greatest influence on the predictive biases when simulating hyporheic exchange. To investigate this, we build a highly parameterized HydroGeoSphere model of the Steinlach River Test Site in southwest Germany as a reference. This model is then modified with simpler bathymetries, evaluating the changes to hyporheic exchange fluxes and transit time distributions. Results indicate that simulating hyporheic exchange with a high‐resolution detailed bathymetry using a three‐dimensional fully coupled model leads to nested multiscale hyporheic exchange systems. A poorly resolved bathymetry will underestimate the small‐scale hyporheic exchange, biasing the simulated hyporheic exchange towards larger scales, thus leading to overestimates of hyporheic exchange residence times. This can lead to gross biases in the estimation of a catchment's capacity to attenuate pollutants when extrapolated to account for all meanders along an entire river within a watershed. The detailed river slope alone is not enough to accurately simulate the locations and magnitudes of losing and gaining river reaches. Thus, local bedforms in terms of bathymetric highs and lows within the river are required. Bathymetry surveying campaigns can be more effective by prioritizing bathymetry measurements along the thalweg and gegenweg of a meandering channel. We define the gegenweg as the line that connects the shallowest points in successive cross‐sections along a river opposite to the thalweg under average flow conditions. Incorporating local bedforms will likely capture the nested nature of hyporheic exchange, leading to more physically meaningful simulations of hyporheic exchange fluxes and transit times.