Comparison of Experimentally and Theoretically Determined Infiltration in Coarse Textured Soil

Though it is vital to estimate infiltration as one of the key factors in effective management of water resources, only few studies have been carried out either to determine the infiltration or to compare the performance of infiltration models for coarse textured soils. Thus, the present study was conducted to accomplish two objectives. First to estimate the Horton’s infiltration model parameters for coarse textured soils (particle size distribution greater than 0.075 mm, according to the Unified Soil Classification System) and to compare the infiltration capacities estimated by the model with those measured in the field. Second to measure the infiltration in the coarse textured soil using both single and double ring infiltrometers and to compare them. Study location was Hapugala area in Galle District, Sri Lanka. In this study, the least squares fitting technique was employed to estimate the Horton’s model parameters from the field measured data. A good agreement was found between the model estimated infiltration values and those measured at field. Horton’s infiltration model estimations fitted very well with much coarse textured soil. The highest difference between the single and double ring infiltrometer measurements were also observed for the much coarse textured soil. Overall, the infiltration measurements by the double ring infiltrometer were 20-35% lower, on average, than that of the single ring infiltration measurements suggesting considerably high infiltration along the lateral direction in the single ring compared to the double ring infiltrometer.