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首页> 外文会议>Conference on Remote Sensing for Agriculture, Ecosystems, and Hydrology IV, Sep 22-25, 2002, Agia Pelagia, Crete, Greece >Estimating Soil Hydraulic Properties from Time-Series of Remotely Sensed and In-situ Measured Topsoil Water Contents
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Estimating Soil Hydraulic Properties from Time-Series of Remotely Sensed and In-situ Measured Topsoil Water Contents

机译：从遥感和就地测量的表层土壤水含量的时间序列估算土壤水力特性

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摘要

Soil hydraulic properties are needed in many applications. One of the most difficult quantities to assess is the hydraulic conductivity function. One reason for this is the influence of soil structure on the infiltration capacity. In this paper we present an approach to estimate the hydraulic properties based on time-series of water contents measured in the topsoil of an experimental field plot. Based on the van Genuchten-Mualem model for the soil hydraulic functions we investigate how these properties affect the dynamics of the topsoil water content. We postulate that the water retention curve can be estimated from the range of the top soil water contents observable in the field. The experimental evidence obtained in the plot experiment supports this theoretical conjection. With regard to the hydraulic conductivity function simulations of the drying process demonstrate that there is no straightforward, linear effect of the saturated conductivity K_s on the drying rate. Depending on the initial conditions and the water retention curve drying may be faster or slower with increasing values of K_s. Despite this non-linear behavior the simulation results indicate that for certain soils the influence of soil structure on the conductivity function may be observed by monitoring diurnal cycles of water content. The lack of these cycles in the measured data points to a small K_s-value for the soil matrix of the experimental plot. This is in agreement with the infiltration patterns observed on that plot. A further way to detect bimodal pore-size distributions consists in measuring during a number of drying periods that differ substantially in the initial water distribution in the profile. Simulations show larger effects on the drying rate caused by larger K_s-values.
机译：在许多应用中都需要土壤水硬性。最难评估的量之一是水力传导率函数。原因之一是土壤结构对入渗能力的影响。在本文中，我们提出了一种基于在实验田地表层土壤中测得的水含量时间序列估算水力特性的方法。基于van Genuchten-Mualem模型的土壤水力学函数，我们研究了这些特性如何影响表土水分的动态。我们假设保水曲线可以根据田间可观测到的最高土壤含水量范围来估算。在地块实验中获得的实验证据支持了这一理论推测。关于干燥过程的水力传导率函数模拟表明，饱和电导率K_s对干燥速率没有直接的线性影响。取决于初始条件和保水曲线，随着K_s值的增加，干燥可能更快或更慢。尽管存在这种非线性行为，但仿真结果表明，对于某些土壤，可以通过监测水分的昼夜循环来观察土壤结构对电导率函数的影响。在测量数据中缺少这些循环，表明该试验区的土壤基质的K_s值较小。这与在该图上观察到的渗透模式一致。检测双峰孔径分布的另一种方法是在多个干燥期间进行测量，这些干燥期间的轮廓中初始水分布有很大不同。模拟表明，较大的K_s值对干燥速率有较大影响。

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