A new Commonwealth scientific study has confirmed the Capes region is facing serious declines in annual rainfall. An innovative project led by CSIRO and Australian Nuclear Science Technology Organisation scientists examining Margaret River’s caves confirmed rainfall was significantly reduced compared with late 20th century tallies. The project saw scientists study stalagmites in local caves to confirm rainfall recharge of the region’s groundwater aquifers had declined. “In a world-first study, we have used caves to show the decades-long decline in rainfall in south-west Australia has reduced the replenishment of groundwater in the region to an 800-year low,” the report authors said. “Rainfall across south-west Australia has been decreasing since the late 1960s. “The region’s drying climate means rainfall may no longer be reliably replenishing its groundwater.” The news comes in stark focus to a positive report last month about the consequences of the 2021 Calgardup bushfire which razed big sections of the Leeuwin-Naturaliste National Park which is home to Margaret River-Busselton Tourism Association attractions including Lake Cave. MRBTA reported declining water levels in its namesake attraction had reversed after more rainfall found its way into the karst system due to destruction of native ground cover. Nonetheless, the Lake Cave news came after a decade-long MRBTA project to protect dwindling water levels to protect ecosystem health and imperilled insects and stygofauna. A Department of Water and Environmental Regulation spokesperson said the effects of climate change continued to guide its groundwater allocation program. “The Cape-to-Cape region is home to many iconic places that hold strong ecological, cultural, and social values for Western Australians, and are at risk from climate change,” they said. “Understanding the impacts of climate change and how this affects our groundwater resources is part of our everyday water management and is built into our water allocation planning. “This includes supporting vulnerable cave systems by restricting where bores can be drilled.” Nature Conservation Margaret River general manager Drew McKenzie said the study’s findings were “deeply concerning” when groundwater was facing increased demand. “It underlines the critical importance of how we manage all our water resources, including Wooditjup Bilya,” he said. “We know that for every onr per cent decline in rainfall, the flow of the Margaret River declines by 5 per cent, making it acutely vulnerable.” Part of the not-for-profit’s work was to ensure the river’s health and vitality. The scientific study examined mineral deposits linked to rainfall and found changes in oxygen isotopes from water flowing through limestone clearly showed a stark decline in recent decades compared with the mineral record of the past.