Physical controls and predictability of stream hyporheic flow evaluated with a multiscale model
Physical controls and predictability of stream hyporheic flow evaluated with a multiscale model
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使用多尺度模型评估河流潜流的物理控制和可预测性
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发表时间：
2012
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通讯作者：
A. Packman
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作者：
S. H. Stonedahl;J. Harvey;J. Detty;A. Aubeneau;A. Packman
改进预测的潜流交换容易测量的物理变量的基础上，需要改善流域溶质运移和反应过程的评估。在这里，我们比较物理为基础的模型预测的印第安纳州流示踪剂的结果解释使用瞬态存储模型（TSM）。我们对基于物理的多尺度模型（MSM）进行了参数化，该模型具有测量的河流平面形状和流量、流速、河床水力传导率和孔隙度以及不同空间尺度下的河床地形（即，涟漪、条形图和范围标度）。我们预测的潜流交换通量和潜流停留时间使用MSM。连续时间随机游走（CTRW）模型被用来转换MSM输出到流溶质运移的预测，我们比较了现场观测和TSM参数通过拟合溶质运移数据。MSM模拟表明，通过较小的地形特征（如波纹）进行的地表-地下交换比通过较大的地形特征（如沙洲）进行的交换快得多。然而，潜流交换的变化与地下水流量的非线性，由于在不同的地形尺度上引起的流动之间的相互作用。MSM模拟表明，地下水排放显着减少了进入地下水的体积和时间，它花在地下。MSM的交换时间尺度也比示踪剂注射方法观察到的要长。示踪剂数据，和相应的TSM拟合，受到示踪剂测量灵敏度和背景示踪剂浓度估计的不确定性的限制。我们的研究结果表明，在广泛的空间和时间尺度上，而不是离散过程的表面-地下水文相互作用的连续体强烈影响的潜流交换率和模式。
Improved predictions of hyporheic exchange based on easily measured physical variables are needed to improve assessment of solute transport and reaction processes in watersheds. Here we compare physically based model predictions for an Indiana stream with stream tracer results interpreted using the Transient Storage Model (TSM). We parameterized the physically based, Multiscale Model (MSM) of stream‐groundwater interactions with measured stream planform and discharge, stream velocity, streambed hydraulic conductivity and porosity, and topography of the streambed at distinct spatial scales (i.e., ripple, bar, and reach scales). We predicted hyporheic exchange fluxes and hyporheic residence times using the MSM. A Continuous Time Random Walk (CTRW) model was used to convert the MSM output into predictions of in stream solute transport, which we compared with field observations and TSM parameters obtained by fitting solute transport data. MSM simulations indicated that surface‐subsurface exchange through smaller topographic features such as ripples was much faster than exchange through larger topographic features such as bars. However, hyporheic exchange varies nonlinearly with groundwater discharge owing to interactions between flows induced at different topographic scales. MSM simulations showed that groundwater discharge significantly decreased both the volume of water entering the subsurface and the time it spent in the subsurface. The MSM also characterized longer timescales of exchange than were observed by the tracer‐injection approach. The tracer data, and corresponding TSM fits, were limited by tracer measurement sensitivity and uncertainty in estimates of background tracer concentrations. Our results indicate that rates and patterns of hyporheic exchange are strongly influenced by a continuum of surface‐subsurface hydrologic interactions over a wide range of spatial and temporal scales rather than discrete processes.