Using a Scaled Fuzzy Model for Simulating Soil Water Infiltration

Investigation of water infiltration process in soil is an important step in soil water movement and, therefore, of interest to different researchers. Fuzzy set theory can be used to simulate soil water infiltration by considering variability and uncertainty in the effective parameters. In this research, a scaled fuzzy model for simulating water infiltration in unsaturated soil is presented. For this purpose, the Richard’s equation was scaled to obtain the fuzzy training network and subsequent fuzzy rules for a wider range of soils. The fuzzy rules were extracted using large training networks made from numerical solution of scaled Richard’s equation. The scaled fuzzy model for the specified boundary conditions is able to simulate the flow for all soils with the specified shape parameter (n) value. Comparison of the results of the fuzzy model and the numerical solution of the Richard’s equation showed that the fuzzy model can well simulate water infiltration in unsaturated soils (NRMSE value between 3% and 4.5%) and the scaled fuzzy model is capable of simulating a wide range of different soils with the same shape parameter (n) (NRMSE value between 1.2% and 1.5%). The scaled fuzzy model was modified to fit a series of fuzzy rules for a range of shape parameter (n) variable.