An analytical solution for a water budget model in an unsaturated zone

A water budget model modified from Kim et al. (1996) was developed to estimate the amount of infiltration, surface runoff, evapotranspiration and groundwater recharge in unsaturated soil profiles on the basis of hydraulic and meteorological data. Soils of sandy loam and silt loam derived from Mualem (1976) are used in conjunction with daily rainfall data to examine the model. A comparison between the proposed model and the Kim model is also presented. Sensitivity analysis indicates that soil water parameters significantly affect the amount of four fluxes either in soil wetting or unsaturated zone drainage. Results of the proposed model show a slightly smaller amount of cumulative infiltration than the Kim model in each kind of soil. In addition, the amount of cumulative groundwater recharge in the Kim model is less than in the proposed model. Mass balance and residual moisture content obviously affect the results of model evaluation. Therefore, the proposed model is more predictive of actual conditions than the Kim model.