利用HYPROP系统测定土壤水分参数的优缺点及改进

介绍了HYPROP非饱和导水率及土壤水分特征曲线测量系统的测定原理,对其优缺点进行了分析,并提出了相应的改进措施。以两种粉壤土和一种壤土共三种供试土壤为例,利用HYPROP系统测定了低吸力范围内土壤的水分特征曲线及非饱和导水率,其在低吸力范围内测量数据量大,精度高,但不能测定高吸力范围的土壤水分特征曲线。针对HYPROP系统测定范围仅限于低吸力的不足,用快速离心法测定了负压为15×103 hPa下的土壤含水量,提供了3种土壤在高吸力下土壤水分特征曲线的控制点,利用Van Genuchten-Mualem经验公式拟合得到了土壤水分特征曲线的经验参数值。实验结果表明,在高吸力范围增加一个土壤水分特征曲线的控制点,可将HYPROP系统所测定的水分特征曲线在高吸力范围内得到延伸,更好地一个完整的土壤水分特征曲线。HYPROP系统对导水率K的测量范围窄,拟合效果不佳,如果能给出实测的饱和导水率值,能得到较好的结果。

Using HYPROP System to Measure Hydraulic Conductivity and Soil Water Characteristic Curve WANG Xiao-Lei1 , HUANG Shuang1 , HUANG Jie-sheng1 , PENG Zi-yun1

HYPROP System can continuously measure both soil water characteristic curve and unsaturated hydraulic conductivity(K(h)) at the same tine within the low water tension area.But HYPROP System fail to work within high pressure range.Therefore,it is unreliable to extrapolate the soil water characteristic curve within a high water tension area.Contraposing this shortage,the soil water cotent at high pressure(15×103 hPa) is measured by using the Centrifugal Method.Based on Van Genuchten-Mualem model,the soil water characteristic curve is evaluated by using the data from HYPROP System and one control points from the Centrifugal Method.Three test soil samples are tested in this paper.The results show that:①adding a control points at high water tension makes the extrapolation of Soil Water Characteristic Curve more reliable;② the pressure range that HYPROP System that can measure K(h) of soil is narrow.Also,to better evaluate the parameters,saturated hydraulic conductivity(Ks) should be provided.