Recommended daily rainfall-runoff model for Australian hydrology consulting

Abstract

Australian consulting engineers widely use the Australian Water Balance Model (AWBM) to estimate runoff at a daily time-step. AWBM is a simple conceptual rainfall-runoff model that has similar complexity to many other models of this type. Here, we compare the performance of AWBM against three other conceptual rainfall-runoff models – SIMHYD, IHACRES and GR4J – that are used in Australia and around the world. The comparison is based on calibration and evaluation of model performance under current conditions as well as under changing conditions, indicative of likely future hydroclimate. Across all the comparisons, GR4J performed the best of the four models. SIMHYD and IHACRES had similar performance to each other, but were slightly inferior to GR4J, while AWBM was the worst performing model. GR4J was clearly the best model under current conditions, but its outperformance reduced under contrasting conditions. We recommend industry practitioners consider replacing AWBM with GR4J for their modelling requirements when modelling current conditions. For contrasting conditions GR4J is a very good selection, but care needs to be taken when catchment annual rainfall–runoff relationships shift under prolonged drying, when IHACRES may also prove to be a good selection.