The influence of riverbed heterogeneity patterns on river-aquifer exchange fluxes under different connection regimes
The influence of riverbed heterogeneity patterns on river-aquifer exchange fluxes under different connection regimes
复制标题
DOI：
10.1016/j.jhydrol.2017.09.031
复制
发表时间：
2017-11
影响因子：
6.4
通讯作者：
Qi Tang;W. Kurtz;O. Schilling;P. Brunner;H. Vereecken;H. Franssen
中科院分区：
文献类型：
--
作者：
Qi Tang;W. Kurtz;O. Schilling;P. Brunner;H. Vereecken;H. Franssen
河床水力传导率 (K) 是预测河流与含水层之间交换通量的关键参数。在本研究中，利用完全集成的水文模型 HydroGeoSphere 模拟复杂、可变的饱和地下流，探讨了非均质性模式的作用。使用蜿蜒河道形式的非多高斯模式，利用异质河床构建了合成的 3-D 河流含水层参考模型。数据同化用于测试不同河床K模式再现水头、河床K和河流-含水层交换通量的能力。测试了河床下的完全饱和和可变饱和条件。采用集合卡尔曼滤波器（EnKF）对四种类型的河床K场地质统计模型进行了数据同化实验：（i）空间均质，（ii）多高斯分布非均质，（iii）非多高斯分布非均质（渠道化结构）和（iv）非多高斯分布非均质（椭圆结构）。对于所有数据同化实验，状态变量和河床K均通过同化水头进行更新。对于饱和条件，异质地质统计模型比均质近似可以更好地描述净交换通量。在三种异构模型中，非多高斯模型的性能优于多高斯模型的性能，但两个测试的非多高斯模型彼此之间的性能差异很小。对于可变饱和条件，多高斯模型和齐次模型的表现明显比两个非多高斯模型差。两个非多高斯模型在性能上没有表现出太大差异。这清楚地表明表征河床的异质性非常重要。此外，特别是在可变饱和流量条件下，河床K的均值和方差不能为交换通量表征提供足够的信息，而河床K的附加直方图信息为交换通量的再现提供了关键信息。
Riverbed hydraulic conductivity (K) is a critical parameter for the prediction of exchange fluxes between a river and an aquifer. In this study, the role of heterogeneity patterns was explored using the fully integrated hydrological model HydroGeoSphere simulating complex, variably saturated subsurface flow. A synthetic 3-D river-aquifer reference model was constructed with a heterogeneous riverbed using non-multi-Gaussian patterns in the form of meandering channels. Data assimilation was used to test the ability of different riverbedKpatterns to reproduce hydraulic heads, riverbedKand river-aquifer exchange fluxes. Both fully saturated as well as variably saturated conditions underneath the riverbed were tested. The data assimilation experiments with the ensemble Kalman filter (EnKF) were carried out for four types of geostatistical models of riverbedKfields: (i) spatially homogeneous, (ii) heterogeneous with multi-Gaussian distribution, (iii) heterogeneous with non-multi-Gaussian distribution (channelized structures) and (iv) heterogeneous with non-multi-Gaussian distribution (elliptic structures). For all data assimilation experiments, state variables and riverbedKwere updated by assimilating hydraulic heads. For saturated conditions, heterogeneous geostatistical models allowed a better characterization of net exchange fluxes than a homogeneous approximation. Among the three heterogeneous models, the performance of non-multi-Gaussian models was superior to the performance of the multi-Gaussian model, but the two tested non-multi-Gaussian models showed only small differences in performance from one another. For the variably saturated conditions both the multi-Gaussian model and the homogeneous model performed clearly worse than the two non-multi-Gaussian models. The two non-multi-Gaussian models did not show much difference in performance. This clearly shows that characterizing heterogeneity of riverbedKis important. Moreover, particularly under variably saturated flow conditions the mean and the variance of riverbedKdo not provide enough information for exchange flux characterization and additional histogram information of riverbedKprovides crucial information for the reproduction of exchange fluxes.