Groundwater flow, transport, and residence times through topography‐driven basins with exponentially decreasing permeability and porosity
Groundwater flow, transport, and residence times through topography‐driven basins with exponentially decreasing permeability and porosity
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DOI：
10.1029/2010wr009370
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发表时间：
2010-11
影响因子：
5.4
通讯作者：
M. Cardenas;Xiaowei Jiang
中科院分区：
文献类型：
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作者：
M. Cardenas;Xiaowei Jiang
在本文中，我们调查的影响，系统和本地的非均质性对地下水流量，运输和停留时间分布（RTD）的盆地，地下水流地形驱动。系统非均质性由深度指数递减的水力传导系数和孔隙度表示，局部非均质性由分散度表示。一个简单的流域与一个流系统和嵌套的本地和区域系统的流域的RTD逐渐演变为幂律RTD更显着的系统异质性。孔隙力学性质的指数下降增强了浅层循环，并抑制了深层和区域流动，导致大部分区域的冲洗时间更长，而较浅的部分则迅速冲洗溶质。因此，较深的盆地导致更持久和明显的幂律RTD时，孔隙力学性能系统地随深度下降。由于与局部流动池相关的停滞区和由于更深的不动区，对RTD的单独贡献被确定;每种都导致不同的拖尾行为。局部非均匀性通过使拖尾开始更早而略微增强幂律RTD，但不影响RTD的后期时间部分。系统的深度相关非均质性是控制地下流体循环和相关RTD的重要因素。它对生成幂律RTD有重要贡献。
In this paper, we investigate the effects of systematic and local heterogeneity on groundwater flow, transport, and residence time distributions (RTDs) of basins where groundwater flow is topography driven. Systematic heterogeneity is represented by an exponentially depth‐decreasing hydraulic conductivity and porosity, and local heterogeneity is represented by the dispersivity. The RTDs for both a simple basin with one flow system and a basin with nested local and regional systems gradually evolve to a power law RTD with more pronounced systematic heterogeneity. Exponential decrease of poromechanical properties enhances shallow circulation and subdues deep and regional flows leading to longer flushing times for the large part of the domain, while the shallower portions flush solutes rapidly. Therefore, deeper basins lead to more persistent and pronounced power law RTDs when the poromechanical properties systematically decrease with depth. Separate contributions to the RTD due to stagnation zones associated with local flow cells and due to deeper immobile zones were identified; each leads to a different tailing behavior. Local heterogeneity slightly enhances the power law RTD by causing the tailing to begin earlier but does not affect the late time portion of the RTD. Systematic depth‐dependent heterogeneity is an important factor controlling the circulation and associated RTDs of subsurface fluids. It contributes significantly to generation of power law RTDs.