Simulation of Water Movement through Unsaturated Infiltration- Redistribution System

This paper deals with the movement of water in a natural unsaturated zone, focusing on infiltration-redistribution system. Infiltration refers to the downward movement of water due to the gravitational force and redistribution defines the upward movement of water due to the capillary rise. Under natural conditions, the movement of water through an infiltrationredistribution depended upon the relations among water content, hydraulic conductivity and tension of soil pore. Various combinations of water balance concepts, Richards’ equation, soil-physics theory and capillary height concepts were applied to mathematically model the movement of water through infiltration-redistribution system. The accuracy and computational efficiency of the developed model were evaluated for the case study. Besides the laboratory scale sand/soil columns with the inner diameter of ۱۰.۴ cm were investigated in order to provide the supporting data for model calibration. Sand/soil layers were packed with a bulk density of ۱.۸۰ and ۱.۲۵ g/cm۳, respectively. The infiltration was sprayed uniformly at the soil surface with the constant rate of ۶۶.۱ and ۷.۱۸ cm۳/h for sand and soil columns, respectively. The redistribution process was developed by which water arriving at the column base enter to the sand/soil column due to capillary rise. The laboratory observations were simulated using the developed model. The results indicate that the developed model could well estimate the movement of water in the infiltration-redistribution system that observed in the case study and the experiments.