Jun-Ying Chen1, Zhi-Tao Zhang1*, Ying Meng 2 , Cheng Hong 3, Delan Zhu1
1. Northwest Agriculture& Forestry University
 2. Shaanxi University of Science & Technology
3. China Water Huaihe Planning ,Design and Research Co.,Ltd

Soil water repellency is defined as the situation that soil is not wet spontaneously when water is applied. Soil water repellency is a factor which may cause the reduction in soil infiltration capacity and increase the risk of erosion. It is critically important for irrigation with low quality water such as wastewater. Soil hydrophobicity is mostly extreme when the soils are dry. Yet, Soil hydrophobicity will decline and eventually disappear with the soils getting wet. The present research work studied the relationship between the soil water repellency and soil moisture by measuring Water Drop Penetrate Time (WDPT) with the use of 6 different water repellent soils collected from Israel. A single-peak distribution was found for expressing the relationship between the water repellency and water moisture statistically. Three mathematic models, namely, Gaussian, Lorentzian and lognormal distributions, were used for fitting the models by regression analysis, and the Lorentzian distribution was found to be the best model for the practical use, which was confirmed by comparing the measured data and predicted data (R2=0.89). 
Keywords: Soil water repellency, Soil moisture, Modeling, Distribution