Mining history to protect Victorian rivers

La Trobe archaeologists dig into Victoria’s long history of gold mining to uncover new ways to protect our rivers.

Professor Susan Lawrence is acting Co-Director of the Centre for the Study of the Inland and a Professor in the Department of Archaeology and History. In 2015, the research team she leads was awarded a grant to evaluate how historical gold mining has shaped river systems in Victoria.

Using old mines department records from the nineteenth century, the team’s documentary research enabled them to calculate that around 600 million cubic metres of polluted sediment was dumped into Victorian rivers over a 50-year period.

Working with geomorphologists and environmental chemists, the team completed fieldwork on three of river systems significantly affected by historical gold mining in Victoria: the Loddon River in central Victoria, the Leigh River south of Ballarat, and tributaries of the Owens River. This research unearthed a wealth of information that helps inform modern-day river management and ecological research.

"Scientists and the environmental managers use baseline river studies that go back to around the 1950s. They aren’t aware of all of the change that had already taken place. Sediment has buried the original floodplain surfaces. Areas you would normally expect to be really rich parts of the ecosystem with all their biodiversity, plants and orchids right next to the rivers, all of that’s been blanketed by mine tailings. All of the seed banks that people want to use for doing remediation work in those areas are buried under a couple of metres of sediment.’

Part of Professor Lawrence’s work also involves identifying ‘sand slugs’; essentially, a plug of remnant gravel and sand that clogs up sections of a river and is pushed downstream after major storm events. Sand slugs are still moving through the river systems from mining that finished up to 100 years ago.

The next phase of this project involves identifying which parts of the mining process generated mercury, and where that mercury sits in the environment today.

"We know from our documentary research there was a considerable amount of mercury being discharged into Victorian rivers, and we think it is important to know where it is. The Victorian and Federal governments have both identified that managing what they call legacy and abandoned mines is a significant problem they don’t have enough data about. This project is really about contributing to that data."