Over the past three decades, more than half the water flow in a section of the Murrumbidgee River—one of Australia’s longest waterways—has been lost, primarily due to dam infrastructure and water diversions, according to a recent study. Researchers from the University of New South Wales (UNSW) examined the impact of irrigation and dam construction on the lower Murrumbidgee River, tracking changes in natural water flow since the 1890s. Their findings, published in the Journal of Environmental Management, indicate that human activities have significantly altered the river’s flow patterns, affecting critical ecosystems. The study reported that diversions, alongside the increased water demand from Canberra, have reduced water flows at Hay, located in southwestern New South Wales (NSW), by 43% between 1958 and 2018. More recent data revealed even greater reductions, with water flow decreasing by 55% over the 30-year period from 1988 to 2018. According to researchers, the decline in water availability has had severe consequences, particularly for the Lowbidgee Floodplain, the largest wetland along the river, which relies on regular flooding to maintain its ecosystems.
Jan Kreibich, a doctoral candidate at UNSW and lead researcher of the study, emphasized the importance of periodic flooding for the floodplain’s health, stating, “The Lowbidgee Floodplain depends on regular inundation. Without it, entire ecosystems are collapsing.” The research team used historical data on rainfall and natural flow from the early 1900s, predating the establishment of dam infrastructure and irrigation systems, to simulate what the river’s natural flow might have been without these human interventions. By comparing this model with actual water flow records, they were able to gauge the degree to which human activities have disrupted the river’s natural state.
A significant aspect of the findings was the increased duration between major flood events, which extend over the riverbanks. Such floods are crucial for the survival of wetlands along the Murrumbidgee River. The research found that the interval between these overbank flows had more than doubled, changing from an average of once every two years to once every 4.4 years. This shift has severely impacted the frequency and intensity of flooding that sustains the surrounding wetlands, posing risks to biodiversity and ecosystem stability.
Further compounding the river’s issues, the study predicts that climate change could exacerbate water shortages, potentially reducing river flows by an additional 7% to 10% from 2047 to 2075. Professor Richard Kingsford, the Director of UNSW’s Centre for Ecosystem Science and co-author of the study, emphasized the compounding effect of climate change. He explained that the environmental impacts of climate breakdown, while pressing, exacerbate an already precarious situation due to water diversions for irrigation and urban demands. He noted that the river system’s environmental flow is currently only a fraction of what it once was, calling on governments to prioritize water policy that safeguards these essential flows. Conservationists have already observed the impact of diminished water flows. Bradley Clarke-Wood, the wetland birds coordinator at BirdLife Australia, explained that the reduction in wetland inundation has affected bird populations in the region. He noted that waterbirds depend on the wetlands for breeding, which is contingent upon the volume and duration of flood events. “Any reduction in water availability and flood duration puts the next generation of birds under increased pressure, limiting their breeding success,” he said.
The study’s findings also underline the urgency for policymakers to address both environmental flow management and climate change. Dr. Paul Sinclair from the Australian Conservation Foundation expressed concerns over the continued degradation of river ecosystems like the Murrumbidgee, stressing that rivers will deteriorate further if they remain disconnected from their floodplains. “Rivers like the Murrumbidgee die if they lose connection to their floodplain,” Sinclair stated, urging federal and state governments to implement measures to ensure rivers maintain sufficient flow to survive the challenges posed by climate change. The research points to an urgent need for sustainable water management strategies to protect the Murrumbidgee and its associated wetlands from further environmental degradation. Effective management requires balancing urban, agricultural, and ecological needs to ensure the river and its ecosystems can endure increasing demands and environmental pressures. By enacting policies that safeguard environmental flows and address climate impacts, policymakers can help preserve the biodiversity and ecological health of the Murrumbidgee River, providing a sustainable path forward for one of Australia’s vital water systems.
