Evaluations of the CREAMS model. III. Simulation of the hydrology of vertisols

Abstract

The CREAMS hydrology model was evaluated for two Vertisols, each with three fallow management strategies, by comparing predictions of runoff, soil moisture and drainage with 5-8 years of measured data. Model parameter values were derived by: (i) using a combination of measured site characteristics and published values, and (ii) optimizing selected parameters, particularly the runoff parameter (curve number). With parameter values from published sources, runoff was overpredicted by 1 to 39%; good estimates of total soil moisture were obtained. Using optimized curve numbers, runoff was predicted well (daily, r2 = 0.83; monthly, r2 = 0.92; annual, r2 = 0.94). Total soil moisture values were predicted well, the main source of error being from overprediction of transpiration. Errors in predicted runoff caused little of the error in predicted total soil moisture. The distribution of soil moisture in the soil was poorly predicted. Drainage predictions were similar to estimates from steady-state solute mass balance. Optimized curve numbers derived in this study provide parameter values for modelling the water balance of self-mulching Vertisols. Values of other model parameters, derived from field measurements and published sources were near optimal, and predictions were not improved by adjusting the more sensitive of these parameters. The model is considered adequate for many practical applications. Some enhancements to the model are suggested.