Water quality impacts from post-fire erosional events: a case study from a peatland within the Greater Blue Mountains World Heritage Area

Peatlands occur globally and are known to store significant amounts of water and key nutrients such as carbon, nitrogen, and phosphorus. Extensive research has been conducted on peat in the Northern Hemisphere, however, research is limited for Australian peatlands. A peatland at Kings Tableland within the Greater Blue Mountains World Heritage Area was assessed after a period of drought (2017-2019), severe bushfires and a high rainfall event (which occurred within a six-week period in 2020) to explore the export of nutrients, including carbon, nitrogen, and phosphorus into downstream waterways. The entire study site (4.74 ha) was burnt (at high to extreme severity) in 2019-2020, and a subsequent heavy rainfall event resulted in an estimated export of 3.46 t of carbon, 0.14 t of nitrogen, and 0.03 kg of phosphorus from the site. The total loss of peat material across the site during this event was estimated at 58 t. This equates to a water storage loss of approximately 0.03 ML from this peatland in less than six weeks. Peatlands are a precious resource, however, peat loss due to desiccation, fire, and erosion can significantly impact water storage and nutrient export. This has implications for downstream water quality, including higher sediment loads, the export of key nutrients which may lead to eutrophication, and increased flows contributing to erosion. The protection of natural hydrology is important for reducing degradation of peatlands and potential impacts to downstream environments.