The impact of groundwater velocity fields on streamlines in an aquifer system with a discontinuous aquitard (Inner Mongolia, China)

Wu, Qiang; Zhao, Yingwang; Xu, Hua

The impact of groundwater velocity fields on streamlines in an aquifer system with a discontinuous aquitard (Inner Mongolia, China) | L’ impact des champs de vitesse de l’eau souterraine sur les lignes de courant dans un système aquifère avec un semi-perméable discontinu (Mongolie intérieure, Chine) El impacto de los campos de velocidad del agua subterránea en las líneas de flujo en un sistema acuífero con un acuitardo discontinuo (Mongolia Interior, China) 地下水流速场对流线的影响: 以中国内蒙古某含有不完整弱透水层的含水系统为例 O impacto dos campos de velocidades da água subterrânea nas linhas de fluxo em um sistema aquífero com um aquitardo descontínuo (interior da Mongólia, China)

2018

Wu, Qiang | Zhao, Yingwang | Xu, Hua

Many numerical methods that simulate groundwater flow, particularly the continuous Galerkin finite element method, do not produce velocity information directly. Many algorithms have been proposed to improve the accuracy of velocity fields computed from hydraulic potentials. The differences in the streamlines generated from velocity fields obtained using different algorithms are presented in this report. The superconvergence method employed by FEFLOW, a popular commercial code, and some dual-mesh methods proposed in recent years are selected for comparison. The applications to depict hydrogeologic conditions using streamlines are used, and errors in streamlines are shown to lead to notable errors in boundary conditions, the locations of material interfaces, fluxes and conductivities. Furthermore, the effects of the procedures used in these two types of methods, including velocity integration and local conservation, are analyzed. The method of interpolating velocities across edges using fluxes is shown to be able to eliminate errors associated with refraction points that are not located along material interfaces and streamline ends at no-flow boundaries. Local conservation is shown to be a crucial property of velocity fields and can result in more accurate streamline densities. A case study involving both three-dimensional and two-dimensional cross-sectional models of a coal mine in Inner Mongolia, China, are used to support the conclusions presented.

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