A seasonal water availability prediction service: opportunities and challenges

Abstract

The purpose of this paper is to outline a proposed seasonal water availability prediction service and, in particular, to describe the modelling components behind the service and their future development. In terms of its climate, Australia has experienced a remarkable decade. The continent has had its warmest period since records began and southern areas have been extremely dry. A seasonal water availability prediction service has been needed in Australia for many years and the Australian Government's recent investment in water information will help address this need. A seasonal climate prediction service has been operating in the Bureau of Meteorology since 1989 but its primary focus has been on rainfall and temperature rather than water availability. Reliable seasonal predictions of streamflows are highly valuable and will have uses for providing water allocation outlooks, informing water markets, planning and managing water use and managing drought. The seasonal water availability prediction service will rely on the development and integration of a number of modelling systems. A statistical prediction system will be based on a Bayesian Joint Probability modelling approach and is expected to provide reliable predictions of 'seasonal' streamflow at lead times of up to several months. Skill (or accuracy) in these predictions will generally exceed those for both temperature and rainfall. In parallel, a 'dynamical' modelling approach will be developed whereby the outputs from climate models will be downscaled to provide the inputs to hydrological models of various degrees of complexity. The key climate models are the Centre for Australian Weather and Climate Research's (CAWCR) Predictive Ocean Atmosphere Model for Australia (POAMA) and, later, the Australian Community Climate and Earth-System Simulator (ACCESS). All prediction systems will be accompanied with verification systems that will provide information on the skill and reliability for both developers and users. In delivering on these responsibilities, the Bureau will rely on considerable research, particularly through CAWCR and the Water Information Research and Development Alliance (WIRADA) agreement between the Bureau of Meteorology and CSIRO. The development of a seasonal water availability service must be user driven - it must ultimately lead to changes in decisions that result in improved outcomes in water resource management. Critical to the development of this service will be a modelling infrastructure that will gradually build in complexity. Investment in modelling efforts will, to a large degree, be driven by scientific and technological capability, cost-benefit considerations, and most importantly, the likely incremental benefits of improved predictions and outcomes for water managers.