The Australian Water Resource Assessment (AWRA) modelling system is developed to enable the Australian Bureau of Meteorology to meet its legislated role in providing an annual National Water Account (NWA) and regular Australian Water Resource Assessment Reports. The system uses available observations and an integrated landscape - river water balance model to estimate the stores and fluxes of the water balance required for reporting purposes. The National Landscape model (AWRA-L) provides gridded estimates of landscape runoff, evapotranspiration, soil moisture, and groundwater recharge/storage/lateral flow, and has been calibrated towards reproduction of a nationwide streamflow dataset. The gridded model structure provides an option of incorporating spatial variability of climate, land cover and soil properties. The water balance fluxes from AWRA-L are used as inputs to the regulated river system model (AWRA-R) to undertake basin scale water balance modelling. The AWRA-R model includes river routing, irrigation diversions, reservoir storage, floodplain inundation and river to groundwater interaction components. All the AWRA modelling components are built within a software architecture which allows seamless interactions between the components at the appropriate spatial and temporal scales. The AWRA modelling system has been implemented across Australia and it provides estimates of water balance fluxes and stores which are substantially better than those from continental scale land surface models and similar to or better than those from widely used conceptual rainfall-runoff models. The system is currently being used for hydrological modelling in a number of large scale projects. The AWRA modelling system provides consistent, robust and repeatable water assessments at catchment, regional and continental scale which can be used to guide future water planning and policy development at multiple scales across Australia.