Prediction of Root-Zone Soil Moisture and Evapotranspiration in Cropland Using HYDRUS-1D Model with Different Soil Hydrodynamic Parameter Schemes

This study provides a comprehensive assessment of the HYDRUS-1D model for predicting root-zone soil moisture (RZSM) and evapotranspiration (ET). It evaluates different soil hydrodynamic parameter (SHP) schemes—soil type-based, soil texture-based, and inverse solution—under varying cropping systems (Zea mays–Glycine max rotation and continuous Zea mays) and moisture conditions (irrigated and rainfed), aiming to understand water transport across different cultivation patterns. Using field measurements from 2002, the SHPs were optimized for each scheme and applied to predict RZSM and ET from 2003 to 2007. The inverse solution scheme produced nearly unbiased RZSM predictions with a root mean square error (RMSE) of 0.011 m3m⁻3, compared to RMSEs of 0.036 m3m⁻3 and 0.042 m3m⁻3 for the soil type-based and soil texture-based schemes, respectively. For ET predictions, comparable accuracy was achieved, with RMSEs of 66.4 Wm⁻2, 69.5 Wm⁻2, and 68.2 Wm⁻2 across the three schemes. RZSM prediction accuracy declined over time in the continuous Zea mays field for all schemes, while systematic errors predominated in the Zea mays–Glycine max rotation field. ET accuracy trends mirrored RZSM in irrigated systems but diverged in rainfed croplands due to the decoupling of ET and RZSM under arid conditions.