Water quality in the Murray-Darling Basin: The potential impacts of climate change

There have been a number of extreme poor water quality events in the Murray-Darling Basin in the last decade, including: hypoxic blackwater events that affected 1,000s of kilometres of river systems and persisted for months; extensive blue-green algal blooms (again stretching for 1,000s kilometres); and massive fish kills associated with destratification of weir pools. It is expected that these, and other extreme water quality events will become more common in the face of a changing climate. This Chapter examines the current and emerging water quality issues in the Murray-Darling Basin, and then explores how climate change, including increased water temperatures, increased ephemerality, increased incidence and severity of bushfires, and increased incidence of severe storms, will likely impact on water quality. As a first step, water quality assessments should be integrated into all flow management decisions, which will require the use of robust conceptual models and predictive, process-based mathematical models to link flow with water quality outcomes at a variety of spatial and temporal scales. To be effective the planning also needs information from well-designed, well-resourced and integrated monitoring programs. Prioritising end-of-valley flows over other competing consumptive uses would also help to mitigate extreme future water quality events.