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1. The importance of hydrologic variability for shaping the biophysical attributes and functioning of riverine ecosystems is well recognised by ecologists and water resource managers. In addition to the ecological dependences of flow for aquatic organisms, human societies modify natural flow regimes to provide dependable ecological services, including water supply, hydropower generation, flood control, recreation and navigation. Management of scarce water resources needs to be based on sound science that supports the development of environmental flow standards at the regional scale. 2. Hydrological classification has long played an essential role in the ecological sciences for understanding geographic patterns of riverine flow variability and exploring its influence on biological communities, and more recently, has been identified as a critical process in environmental flow assessments. 3. We present the first continental-scale classification of hydrologic regimes for Australia based on 120 metrics describing ecologically relevant characteristics of the natural hydrologic regime derived from discharge data for 830 stream gauges. Metrics were calculated from continuous time series (15–30 years of record constrained within a 36-year period) of mean daily discharge data, and classification was undertaken using a fuzzy partitional method – Bayesian mixture modelling. 4. The analysis resulted in the most likely classification having 12 classes of distinctive flow-regime types differing in the seasonal pattern of discharge, degree of flow permanence (i.e. perennial versus varying degrees of intermittency), variations in flood magnitude and frequency and other aspects of flow predictability and variability. Geographic, climatic and some catchment topographic factors were generally strong discriminators of flow-regime classes. The geographical distribution of flow-regime classes showed varying degrees of spatial cohesion, with stream gauges from certain flow-regime classes often being non-contiguously distributed across the continent. These results support the view that spatial variation in hydrology is determined by interactions among climate, geology, topography and vegetation at multiple spatial and temporal scales. Decision trees were also developed to provide the ability to determine the natural flow-regime class membership of new stream gauges based on their key environmental and/or hydrological characteristics. 5. The need to recognise hydrologic variation at multiple spatial scales is an important first step to setting regional-scale environmental flow management strategies. We expect that the classification produced here can underpin the development of a greater understanding of flow-ecology relationships in Australia, and management efforts aimed at prescribing environmental flows for riverine restoration and conservation. [ABSTRACT FROM AUTHOR]

Aim: Stratification of major differences in the biophysical features of landscapes at the continental scale is necessary to collectively assess local observations of landscape response to management actions for consistency and difference. Such a stratification is an important step in the development of generalizations concerning how landscapes respond to different management regimes. As part of the development of a comparative framework for this purpose, we propose a climate classification adapted from an existing broad scale global agro-climatic classification, which is closely aligned with natural vegetation formations and common land uses across Australia. Location: The project considered landscapes across the continent of Australia. Methods: The global agro-climatic classification was adapted by using elevation dependent thin plate smoothing splines to clarify the spatial extents of the 18 global classes found in Australia. The clarified class boundaries were interpolated from known classes at 822 points across Australia. These classes were then aligned with the existing bioregional classification, Interim Biogeographic Regionalization for Australia IBRA 5.1. Results: The aligned climate classes reflect major patterns in plant growth temperature and moisture indices and seasonality. These in turn reflect broad differences in cropping and other land use characteristics. Fifty-two of the 85 bioregions were classified entirely into one of the 18 agro-climatic classes. The remaining bioregions were classified according to sub-bioregional boundaries. A small number of these sub-bioregions were split to better reflect agro-climatic boundaries. Main conclusions :The agro-climatic classification provided an explicit global context for the analysis. The topographic dependence of the revised climate class boundaries clarified the spatial extents of poorly sampled highland classes and facilitated the alignment of these classes with the bioregional classification. This also made the classification amenable to explicit application. The bioregional and subregional boundaries reflect discontinuities in biophysical features. These permit the integrated classification to reflect major potential differences in landscape function and response to management. The refined agro-climatic classification and its integration with the IBRA bioregions are both available for general use and assessment. [ABSTRACT FROM AUTHOR]