مقیاس سازی توامان توابع نگهداشت آب و هدایت هیدرولیکی خاک

Abstract
Scaling methods, which are based on similar media theory, are used to simplify the statistic description of soil spatial variations. To simulate the water flow in heterogeneous soils, simultaneous scaling of soil hydraulic functions, including soil water retention and unsaturated hydraulic conductivity functions, is highly desirable. In the similar media theory, the simultaneous scaling is expected for geometrically similar soils. In this paper, it is indicated that although the geometric similarity is a necessity, it is not sufficient for validation of the similar media theory in the reality. It is shown that, in addition, the values of Kshm2 (β) must be identical in all similar soils (where Ks is the saturated hydraulic conductivity and hm is the median suction head in the water retention curve). To evaluate the theory, method of Tuli et al. (13) was used which applies the similar media theory to the similar soils of Kosugi and Hopmans (4) with identical σ (standard deviation in the log-normal hydraulic models). The method was also generalized such that it can well scale the soil hydraulic functions of the similar soils even where the β values are not identical. The theoretical descriptions were tested by data of 26 soils from UNSODA database. The soils were classified into six groups of similar soils based on the equality of their σ. As it was expected, the method of Tuli et al. did not perform well in the groups in which β values were significantly different. The results also showed that the proposed method can considerably improve the performance of the method of Tuli et al. It was indicated that the performance of the proposed method do not depend on β values and the geometric similarity is the only condition for that.

Keywords: Similar media, Simultaneous scaling, Retention curve, Hydraulic conductivity function