Development of a physically based 1D-infiltration model for irrigated soils

In this study, a simple approach for modeling 1D-infiltration in uniform and layered soils, based on the Green-Ampt equation, is developed and evaluated for three different conditions, i.e., seal free uniform, seal formed uniform and seal formed layered soils. The results are compared with the literature data. Also the model results are compared with the Green-Ampt explicit solution for seal free uniform soils and with 1D-Richards equation for seal formed uniform and layered soils. The developed model performed equally well with the compared models and with the literature data for all three cases. The relative error varies from -2% to 9%, -5% to 2% and -6.2% to 3% in case of seal free uniform soil, seal formed uniform soil and seal formed layered soils, respectively. The reduction in infiltration due to seal formation in uniform soil varies from 10% and 48% for sandy loam and silty clay loam soils, respectively. Similarly, when the soil is considered as three-layered system (sealtillage-subsoil), the reduction in infiltration at 360 min elapsed time due to constant seal condition is 4% and 18% for sandy loam and silty clay loam soils, respectively. Sensitivity analysis of the parameters of seal, tillage layer and subsoil for sandy loam and silty clay loam soils deduced that satiated hydraulic conductivity and moisture difference of the subsoil are the most sensitive parameters when the subseal between seal and tillage layer is saturated. However, no effect of satiated hydraulic conductivity of subsoil and moisture difference of tillage layer on infiltration is found when the subseal between seal and tillage layer is unsaturated. it is also found that the order of parameter sensitivity varied with the seal condition and not with the soil texture. This study reveals that surface seal affects the infiltration process through irrigated soils and hence, inclusion of surface seal in infiltration models is essential for infiltration prediction. The developed ID-infiltration model, which includes surface seal effect, can be used to predict infiltration through seal formed or seal free soil column up to three layers. (c) 2006 Elsevier B.V. All rights reserved.