Concept of the Integrated Hydrological Ensemble Prediction System applied for the Nattai River Catchment, Australia

Reservoir inflow predictions are essential to ensure effective operations of Sydney's main drinking water reservoir. The reservoir's forecast system is based on empirical rainfall forecast scenarios. Those scenarios are only indicators of possible significant future rainfall events. Recently, the Short-Term Ensemble Prediction System (STEPS) has become available in real time, which provides high-resolution rainfall forecast predictions over the catchment. The availability of STEPS rainfall forecast made it possible to develop the Integrated Hydrological Ensemble Prediction System that integrates the STEPS ensemble rainfall forecast with the fully distributed MIKE Systeme Hydrologique Europeen model, which captures the rainfall spatial variability over the catchment and provides ensemble reservoir inflow predictions. The newly developed forecast system is embedded into the existing forecast system. This article describes the development of the forecast system and its implementation to the Nattai River catchment, one of the major inflow sources to Sydney's main drinking water reservoir.