Scaling of Soil Hydraulic Conductivity Function Using Effective Capillary Drive

To estimate spatial variability of soil hydraulic functions, scaling methods were developed and have been widely used. Among these functions, physically based methods have been found more desirable because of possibility of estimating soil hydraulic functions from soil physical properties. In this paper, a new and physically based method has been described for scaling soil hydraulic conductivity function. In this method, use of effective capillary drive (hcM) has been proposed for scaling of soil water suction axis in the hydraulic conductivity function. Using this method, data of all natural soils, from sand to clay, can be presented by a unique exponential curve as reference curve. The approach was validated by 396 sets of hydraulic conductivity data, including all soil texture classes, taken from UNSODA database. To determine hcM, fitting Brooks-Corey and Gardner-Philip models and also a model-free method were used. The results indicated an acceptable performance of the proposed method. Brooks-Corey and Gardner-Philip models and the model-free method results showed the average absolute error of relative hydraulic conductivity between the scaled data and the reference curve as 0.019, 0.056, and 0.059, respectively. In the employed methods, fitting capability of the mentioned models can be taken into account as the only limitation. Thus scaling performance would be well if the mentioned models could fit well the hydraulic conductivity data and vice versa.