Simplified evaporation method for determining soil hydraulic properties
Simplified evaporation method for determining soil hydraulic properties
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DOI：
10.1016/j.jhydrol.2008.04.016
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发表时间：
2008-07-01
影响因子：
6.4
通讯作者：
Durner, W.
中科院分区：
文献类型：
--
作者：
Peters, A.;Durner, W.
蒸发实验通常用于获得土壤的水力性质。在简化的蒸发方法中，如Schindler [Schindler，U.，1980.一个快速的测量器可以测量巴登的水流量和Stechzytinderproben。阿奇·阿克乌普夫兰岑堡角博登克柏林24，1-7]，连续记录两个高度水平处的土壤样品重量和压头。这些测量值的评价依赖于时间、空间和含水量-压头关系的线性化假设。在这篇文章中，我们调查的误差，结果从线性化假设，并显示系统和随机测量误差如何影响保水和导水率数据的计算和土壤水力函数的拟合。我们发现，相对于时间的线性化误差可以忽略不计，如果三次Hermite样条用于数据插值。空间线性化会导致较小的误差，即使在蒸发后期也会出现强烈的非线性压头分布。在蒸发过程的开始，由于忽略了样品中的非线性含水量分布，估计的保留函数中存在偏差，主要影响粗砂或具有结构化孔隙系统的土壤。如果使用测量的积分评估，则可以避免这种误差。我们引入了一个适用的拒绝标准不可靠的渗透系数数据饱和附近，在水力梯度的错误的基础上。张力计的校准误差导致在潮湿范围内的水力特性的有偏估计，而张力计安装位置的误差在干燥范围内产生偏差。数据中的随机误差不会导致显著的偏差，并且如果保水性和传导性函数耦合并且基础模型结构正确，则可以以较小的不确定性来估计参数水力函数。(C)2008 Elsevier B. V.保留所有权利。
Evaporation experiments are commonly used to derive hydraulic properties of soils. In the simplified evaporation method, as proposed by Schindler [Schindler, U., 1980. Ein Schnellverfahren zur Messung der Wasserleitfahigkeit im teilgesattigten Baden an Stechzytinderproben. Arch. Acker-u. Pflanzenbau u. Bodenkd. Berlin 24, 1-7], the weight of a soil sample and pressure heads at two height levels are recorded at consecutive times. The evaluation of these measurements relies on linearization assumptions with respect to time, space and the water content-pressure head relationship. In this article, we investigate the errors that result from the linearization assumptions, and show how systematic and stochastic measurement errors affect the calculation of water retention and hydraulic conductivity data and the resulting fits of soil hydraulic functions. We find that linearization errors with respect to time are negligible if cubic Hermite splines are used for data interpolation. Linearizations in space lead to minor errors, even in the late stage of evaporation where strongly non-linear pressure head profiles emerge. A bias in the estimated retention function results from the negligence of a non-tinear water content distribution in the sample at the begin of the evaporation process, and affects primarily coarse sands or soils with structured pore systems. This error can be avoided if an integral evaluation of the measurements is used. We introduce an applicable rejection criterion for unreliable hydraulic conductivity data near saturation, based on the error in the hydraulic gradient. Calibration errors of tensiometers lead to biased estimates of hydraulic properties in the wet range, whereas errors in tensiometer installation positions yield biases in the dry range. Random errors in data cause no significant bias, and parametric hydraulic functions can be estimated with small uncertainties, if water retention and conductivity functions are coupled and the underlying model structure is correct. (C) 2008 Elsevier B.V. All rights reserved.