By its mathematical formulation, the hydraulic conductivity model of Mualem (1976) is an integral operator which describes the interfunctional relationship between the soil water retention function and the hydraulic conductivity as a function of soil water content. It applies two functions, tortuosity factor T and correlation coefficient G, representing the theoretical kernel of the operator. Since the two functions could not be independently determined, their combined effect on the reduction of the calculated hydraulic conductivity, at any given water content, had been accounted for by a power function of the respective effective saturation. In this study the model is modified by recovering the multiple of the two functions TG under the integral sign over the pore domains. Using experimental data of representative spectrum of soils, the equivalent function to TG is derived as a kernel of the operator. Preliminary results of verification test indicate that the predictive power of the model is enhanced and the prospect for further improvement is high.