Richards Equation at the Hillslope Scale: Can We Resolve the Heterogeneity of Soil Hydraulic Material Properties?
Richards Equation at the Hillslope Scale: Can We Resolve the Heterogeneity of Soil Hydraulic Material Properties?
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DOI：
10.1029/2022wr032294
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发表时间：
2022-11
影响因子：
5.4
通讯作者：
H. H. Bauser-H.;Minseok Kim;W. Ng;Aaron Bugaj;P. Troch
中科院分区：
文献类型：
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作者：
H. H. Bauser-H.;Minseok Kim;W. Ng;Aaron Bugaj;P. Troch
使用理查兹方程对土壤水运动进行基于过程的建模需要描述土壤水力材料特性，这些特性在所有尺度上都具有高度不确定性和异质性。这限制了理查兹方程在超出斑块尺度的更大尺度上的适用性。生物圈 2 号景观演化观测站 (LEO) 的三个山坡的实验能力为观察山坡尺度水工材料特性的异质性提供了独特的机会。我们进行了重力流实验，通过不断的灌溉，含水量不断增加，直到水力传导率与上述灌溉流量相匹配。 LEO 的密集含水量传感器网络可以以米级分辨率绘制水力传导率的异质性图。实验揭示了山坡内的空间结构，主要是垂直趋势，接近地表的导水率最低。然而，相邻传感器之间的差异很大，表明即使在低地轨道也无法完全解决异质性。通过米勒尺度表示模型中的异质性，我们展示了对山坡流量的影响。对于异质性最小的山坡，代表主要结构就足够了。然而，对于整体异质性较大的两个山坡，添加局部异质性的更多细节确实会进一步影响流量。这凸显了理查兹方程的局限性，该方程需要山坡尺度上的材料属性的异质场，并显示出与提高我们对有效参数的理解的相关性，以便能够将基于过程的模型应用于更大的尺度。
Process‐based modeling of soil water movement with the Richards equation requires the description of soil hydraulic material properties, which are highly uncertain and heterogeneous at all scales. This limits the applicability of the Richards equation at larger scales beyond the patch scale. The experimental capabilities of the three hillslopes of the Landscape Evolution Observatory (LEO) at Biosphere 2 provide a unique opportunity to observe the heterogeneity of hydraulic material properties at the hillslope scale. We performed a gravity flow experiment where through constant irrigation the water content increases until the hydraulic conductivity matches the irrigation flux above. The dense water content sensor network at LEO then allows mapping of the heterogeneity of hydraulic conductivity at a meter scale resolution. The experiment revealed spatial structures within the hillslopes, mainly a vertical trend with the lowest hydraulic conductivity close to the surface. However, the variation between neighboring sensors is high, showing that the heterogeneity cannot be fully resolved even at LEO. By representing the heterogeneity in models through Miller scaling we showed the impact on hillslope discharge. For the hillslope with the smallest heterogeneity, representing the dominant structures was sufficient. However, for the two hillslopes with the larger overall heterogeneity, adding further details of the local heterogeneity did impact the discharge further. This highlights the limitations of the Richards equation, which requires the heterogeneous field of material properties, at the hillslope scale and shows the relevance to improving our understanding of effective parameters to be able to apply the process‐based model to larger scales.