Comparisons of a numerical model and a water balance model to quantify soil water balance in root zone of winter wheat

To obtain soil water balance components in root zone of winter wheat, a numerical model and a water-balance model were established and compared in this study based on existing research results and field experimental data of winter wheat seasons from 2007 to 2009 in Shijing Irrigation Scheme in Hebei province, China. The results are as follows :( 1) Mean Sum of Residuals Fraction (MSRF) and Root Mean Square Fraction (RMSF) between actual experimental and stimulated values of soil moisture of two models are both within 15%, but the accuracy of the water-balance model is slightly higher because of the automated parameter optimization function provided by Vensim software which is used to build the water-balance model, (2) two models present close simulated results in cumulative water balance components. Simulated dynamic process lines of actual soil evaporation, crop transpiration and 2m-soil water storage are very close as well, yet the water-balance model gives an upward flux due to capillary rise consideration, (3) compared with the numerical model, the water-balance model has hysteresis effect in simulated seepage process, and the peak of seepage process is slightly lower, which is caused by the roughness in spatial and temporal discretization. (4) less soil parameters are involved in the water-balance model.