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The Murray-Darling River system is perhaps Australia's most important, with significant social, cultural and environmental values including 16 Ramsar listed wetlands. The MDB is home to 2.6 million people and produces about $24 billion worth in agricultural production each year (about one-third of total value for Australia). Hydrologic issues, typified by water availability and quality, have existed for many years, peaking during the Millennium drought from 1997 to 2010. Competing interests (i.e. irrigation, tourism, environmental heath), and the declining flows and water quality during droughts, led governments and water management agencies to consider the risks to water resources in the system in the early-mid 2000s. This paper reviews changes to risks associated with forest dynamics, as identified by - afforestation and bushfire – and considers new issues that have emerged since that analysis. It was found that the potential impacts of bushfire on stream flows were over-estimated in past studies, and that a planned significant afforestation expansion into agricultural and grazing land that was projected to reduce stream flows did not occur. While these two risks now do not seem likely to have significant future impacts on flows, or consequent effects on downstream users, the interaction of elevated CO2 and increasing temperatures on vegetation functioning and subsequent hydrologic consequences at catchment scale require further research and analysis. Reduced rainfall and increased temperatures under future climate change are likely to have an impact on inputs and flows. Uncertainties in how these changes, and feedbacks between climate, drought, more frequent fire and vegetation responses, impact on system hydrology also require further investigation. [ABSTRACT FROM AUTHOR]

Caddisflies comprise a major component of the macroinvertebrate diversity of streams throughout the world. We studied temporal variation in the abundance and diversity of caddisflies of six streams in the monsoonal wet-dry tropics of northern Australia. Abundance and diversity of adult caddisflies were highly seasonal with most activity within wet season months from January to April, with a synchronous pulse of activity in the mid-dry season in two of the three years of study at some sites. Modelling of species richness showed variability among sites in the seasonal patterns of species richness. Multivariate analysis identified seasonal change in assemblage composition. These results are relevant to the design of biodiversity studies on seasonally flowing streams. Surveys of caddisfly diversity are most effectively undertaken during and after the wet season: repeated surveys are required to maximise the detection of the full suite of species occurring at a site. [ABSTRACT FROM AUTHOR]

Understanding long-term trends in streamflow is important for water resource management. In this study, we investigate the long-term streamflow trends at 47 gauging sites within the southern Murray-Darling Basin (MDB), Australia. This study aims to estimate regional streamflow trends while understanding the impact of catchment characteristics on the spatial variation in these trends. To achieve this, we applied a Bayesian hierarchical model (BHM) to make the best use of available streamflow records from multiple sites and catchment characteristics such as climate, terrain, geology, land use and vegetation. The results show that streamflow trends from tested sites are consistently negative, with magnitudes of up to 2.7% per year relative to the annual average flow. We also find that spatial variability in trends can be best linked to differences in average climatic and terrain conditions. This finding can be used to inform future water planning for consumptive and environmental uses in the MDB. [ABSTRACT FROM AUTHOR]

Australia experiences a wide range and increasing incidence of extreme hydrological events, including step changes in stream flows, extreme drought, bushfires followed by heavy rain, and storm events, which impact water availability and water quality. This article discusses the management of these events in the provision of water services in urban Australia. These events are being actively and effectively managed by large water service providers, covering around 80% of the population. But the experience for the remaining 20% is mixed, with smaller service providers often struggling to meet community expectations. This suggests a need for further governance reforms. [ABSTRACT FROM AUTHOR]