The objective of this work was to develop a hypothetical reality of hydrologic response to be used as an error-free synthetic dataset in a larger ongoing study. The hypothetical reality was generated via rigorous simulation of a real system with a comprehensive physics-based model. The simulation was conducted with the Integrated Hydrology Model (InHM); the system is the Tarrawarra catchment located in southeastern Australia. Parameterization of the Tarrawarra boundary-value problem was based on the best available information, which, for example includes rainfall, discharge, and soil-water content data for the last six months of 1996. The InHM-simulated near-surface hydrologic response for the Tarrawarra boundary-value problem compares well (albeit not perfectly) with both the integrated and distributed observations from the catchment. The Tarrawarra-like hypothetical reality of wet season hydrologic response generated in this study is rich enough to be employed as an error-free synthetic dataset for quantitatively evaluating the capabilities/limitations of competing (underlying) modelling techniques. Copyright © 2009 John Wiley & Sons, Ltd.