DISTRIBUTED-PARAMETER HYDROLOGY MODEL (ANSWERS) APPLIED TO A RANGE OF CATCHMENT SCALES USING RAINFALL SIMULATOR DATA .2. APPLICATION TO SPATIALLY UNIFORM CATCHMENTS

The ANSWERS model, modified to include Green and Ampt infiltration, was tested using measured runoff from several tilled, black earth catchments on the eastern Darling Downs, Queensland. Rainfall and runoff data from rainfall simulator plots (1 m(2) and 88 m(2)), and three small catchments (0.07 ha, 0.2 ha and 3.2 ha) were used to test predictions of runoff. Important infiltration parameter values were determined from a separate set of 1 m(2) rainfall simulator plots. Other parameter values were measured directly or estimated from published sources. Measured runoff from the simulator plots and catchments was accurately predicted by the modified ANSWERS; a linear regression explained 93% and 81% of the variation between predicted and measured peak runoff rate and runoff volume, respectively. Runoff was accurately predicted with the modified ANSWERS, as processes controlling runoff from the catchments, including infiltration and routing of runoff, were realistically characterised. This allowed parameter values to be derived independently of runoff, and transported to different size catchments without distortion or optimisation.