spatial variability of infiltration characteristics at watershed scale:a case study of bajgah plain

study of the spatial variability of infiltration characteristics is essential to estimating infiltration parameters on a local scale. the objectives of the present study were to scale the parameters of a philip two-term model for infiltration and survey the variability of infiltration characteristics geostatistically using wastewater in the bajgah catchment. infiltration was measured at 30 points in a random pattern over the study area using double rings. infiltration characteristics in the area showed a low basic infiltration rate for most sites (0.001-0.178 cm/min-1). the philip infiltration model, the best model to describe infiltration characteristics, was fitted to the data. the parameters (sorptivity, hydraulic conductivity) showed wide variation across the sites. the sorptivity-based scaling factor (αs) and the hydraulic-based scaling factor (αa) were computed and the observed infiltration data were scaled based on these values. results showed that scaling achieved using αa was better than that obtained using αs. the optimum scaling factors (αopt) were determined using the least squares method (solver option) and scaling was repeated using αopt. scaling factors based on the arithmetic, geometric and harmonic means of αs and αa were also computed. it was found that αopt and αa scaled the infiltration data more effectively (with lowest sum of squares error) than the other scaling factors. the results showed that the study area has high spatial variability. a map of αa developed using arcgis software showed that αa increased from the center to the surrounding areas as soil clay content decreased.