测试河流-含水层连通性的替代概念模型及其对基流和河流补给过程的影响,Hydrological Processes

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测试河流-含水层连通性的替代概念模型及其对基流和河流补给过程的影响
Hydrological Processes ( IF 2.8 ) Pub Date : 2022-03-13 , DOI: 10.1002/hyp.14545
Tayyab Mehmood ₁ , Gretchen R. Miller ₁ , Peter S. K. Knappett ₂

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本研究模拟了布拉索斯河冲积含水层与德克萨斯州布拉索斯河之间的交换通量动态。在 HYDRUS 2D 中使用横跨河流的小尺度高分辨率样带模拟了河流与含水层之间连接的七个概念模型。这些模型假设了不同的含水层岩性和河流切入深度，并考虑了诸如河床堵塞和渗流面流动等过程。观测到的河流水位值用于指定时变水头边界，并针对附近两个监测井中观测到的水头对模拟进行了测试。近 1.5 年的次小时测量跨越了洪水和干旱时期。最佳拟合概念模型支持河流附近的地下与更广泛的冲积含水层之间的假设水力断开。与先前研究的假设相反，这些数据更符合薄的低 K 结构（例如废弃的古河道）的存在，而不是河床堵塞。在评估的模型范围内，河流与含水层之间的平均净交换量为 0.016 至 12.4 m³ /d/m。大部分变化归因于河床的基流，其范围从 0.18 到 13.1 m ³ /d/m，具体取决于模型。渗流面的交换通量范围（0.004 到 2.37 m ³ /d/m）和从河流到含水层的补给量（0.1 到 5.63 m ³ /d/m）是显着的，但影响不大。基于这些值，概念模型的选择会对用于河流管理的数值模型的准确性产生深远的影响。在整个河段外推，这种不确定性将达到±83 m ³ /s 的流量，相当于河流出口附近流量的34%。

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Testing alternative conceptual models of river-aquifer connectivity and their impacts on baseflow and river recharge processes

This study simulates the dynamics of exchange fluxes between Brazos River Alluvium Aquifer and the Brazos River, TX. Seven conceptual models for the connection between the river and the aquifer were simulated in HYDRUS 2D using small-scale, high-resolution transects across the river. These models assumed varying aquifer lithology and river incision depths and considered processes such as riverbed clogging and seepage face flows. Observed river stage values were used to specify a time-variable head boundary, and the simulations were tested against observed hydraulic heads in two nearby monitoring wells. The nearly 1.5 years of sub-hourly measurements spanned both flood and drought periods. The best-fit conceptual model supported a hypothesized hydraulic disconnection between the subsurface near the river and the wider alluvial aquifer. In contrast to the assumptions of previous studies, these data were more consistent with the presence of a thin, low-K structure (such as an abandoned paleochannel) rather than riverbed clogging. Across the range of models evaluated, the average net exchange between the river and the aquifer ranged from 0.016 to 12.4 m³/d/m. Most of the variability was attributed to baseflow across the riverbed, which ranged from 0.18 to 13.1 m³/d/m depending on the model. The ranges of exchange fluxes across the seepage face (0.004 to 2.37 m³/d/m) and recharge from the river to the aquifer (0.1 to 5.63 m³/d/m) were significant, but not as influential. Based on these values, the choice of conceptual model could have a profound impact on the accuracy of numerical models used for river management. Extrapolated across the entire reach, this uncertainty would amount to ±83 m³/s of discharge, equivalent to 34% of the river's discharge near its outlet.

更新日期：2022-03-13

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