Modelling of flow and transport in unsaturated soils requires information on two fundamental hydraulic properties: the soil water retention curve and relative hydraulic conductivity. A soil's relative hydraulic conductivity is frequently predicted from the soil water retention curve. The most widely used combination is the van Genuchten model for the soil water retention curve and the Mualem model for relative hydraulic conductivity (VGM). Previous studies show that the VGM model underestimates measured relative hydraulic conductivity for soils with fine textures; a sharp drop in relative hydraulic conductivity can be seen near saturation. A new modification of the van Genuchten soil water retention model is proposed with the aim of improving the agreement between predicted and measured relative hydraulic conductivity. The Brooks and Corey‐Burdine model is used to predict relative hydraulic conductivity from the modified van Genuchten soil water retention curve (MVG‐BCB). The modified model assumes independent m and n in the van Genuchten model but with constraints n > 2 and 0 < m < 1. The MVG‐BCB model is evaluated by comparing calculated and measured data for 59 soils that have widely varying soil textures, ranging from sandstone to clay. The MVG‐BCB model improves the agreement between calculated and measured data for both the soil water retention curve and relative hydraulic conductivity. The MVG‐BCB model is closer to measured relative hydraulic conductivity data for most of the selected soils and the sharp drop near saturation is eliminated. Both the modified soil water retention curve and relative hydraulic conductivity functions are smooth curves and can easily be incorporated into vadose zone flow and transport modellings.

中文翻译：

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对Van Genuchten模型的修正，以改进对非饱和土壤相对水力传导率的预测

对非饱和土壤中的流动和传输进行建模需要有关两个基本水力特性的信息：土壤保水曲线和相对水力传导率。通常从土壤保水曲线预测土壤的相对水力传导率。使用最广泛的组合是用于土壤保水曲线的van Genuchten模型和用于相对水力传导率（VGM）的Mualem模型。先前的研究表明，VGM模型低估了质地细密的土壤的相对水力传导率。在饱和附近可以看到相对水力传导率的急剧下降。提出了van Genuchten土壤保水模型的一种新改进，目的是提高预测的和测量的相对水力传导率之间的一致性。Brooks and Corey-Burdine模型用于根据修正的van Genuchten土壤保水曲线（MVG-BCB）预测相对水力传导率。修改后的模型假设独立van Genuchten模型中的m和n，但约束n  > 2和0 <  m  <1。MVG-BCB模型是通过比较59种土壤的计算和测量数据进行评估的，这些土壤具有从砂岩到黏土的多种多样的土壤质地。MVG-BCB模型改善了土壤保水曲线和相对水力传导率的计算数据与实测数据之间的一致性。MVG-BCB模型更接近于大多数选定土壤的实测相对水力传导率数据，并且消除了饱和附近的急剧下降。修改后的土壤保水曲线和相对水力传导率函数都是平滑曲线，可以轻松地纳入渗流区流动和运输模型中。