The description of soil water movement at the field scale requires soil hydraulic material properties. These cannot be measured directly and exhibit an intrinsic multiscale heterogeneity. The estimation of soil hydraulic properties through inverse modeling or data assimilation requires measurements of the state of the system. However, these measurements are typically scarce and do not resolve soil heterogeneity leading to effective material properties with limited predictive capabilities. In a synthetic study at the scale of soil profiles, we explore the possibility to estimate an effective reduced one‐dimensional representation based on only four local water content measurements in a vertical profile located in one‐ and two‐dimensional heterogeneous media. We allow the effective material properties to deviate locally to consider the impact of the small‐scale heterogeneity on the water content measurements. In the synthetic experiments, the estimated reduced one‐dimensional representations predict soil water content and fluxes sufficiently well but can fail to predict the accurate timing and magnitude of infiltration fronts. Cumulative fluxes below the water content measurements were predicted correctly even on short time scales, if evaporation was estimated accurately. However, this proved to be challenging if the local evaporation fluxes above the measurement profile deviated strongly from the average evaporation fluxes of the heterogeneous medium. The one‐dimensional estimation leads to soil hydraulic parameters describing effective material properties that differ from the true material properties to compensate the missing representation of heterogeneity and two‐dimensional flow.

中文翻译：

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基于局部含水量测量数据有效表达土壤异质性的挑战

在田间尺度上描述土壤水分运动需要土壤水硬性材料的特性。这些不能直接测量，并且表现出固有的多尺度异质性。通过逆模型或数据同化来估算土壤水力特性需要测量系统状态。然而，这些测量通常是稀缺的，并且不能解决土壤异质性，从而导致有效的材料特性以及有限的预测能力。在土壤剖面规模的综合研究中，我们探索了仅基于位于一维和二维异质介质中的垂直剖面中的四个局部水分含量测量值来估计有效的简化一维表示的可能性。我们允许有效的材料属性局部偏离，以考虑小尺度异质性对水含量测量的影响。在合成实验中，估计的减少的一维表示可以很好地预测土壤含水量和通量，但可能无法预测入渗前沿的准确时间和大小。如果能准确估算出蒸发量，即使在很短的时间范围内，也能正确预测低于水含量的累积通量。但是，如果测量曲线上方的局部蒸发通量与非均质介质的平均蒸发通量有很大的偏离，这将证明是具有挑战性的。