Environmental context. Australian alpine peatlands are thought to have an important role in maintaining water quality in the associated headwater streams. This study has confirmed that these peatlands can significantly modify stream water through a range of mechanisms, including: nutrient uptake, salt sequestering, and the export of organic carbon. While the significance of this chemical regulation to down stream processes is yet to be fully understood, it is clear that these systems have considerable potential to modify water composition.

Abstract. Heathy Spur 1 (HS-1) is an intact alpine peatland in the Bogong High Plains, Victoria, Australia, that serves as a reference system for understanding the impacts of historical land use practices (cattle grazing, water diversion) and wildfire. The major ion chemistry in the groundwater feed and drainage water at HS-1 was studied over seasonal timescales during ‘dry weather’ periods; conditions that allow a simple hydrological model to be used, where the groundwater is assumed to partition between evapotranspiration and stream discharge. With this model the acid neutralising capacity (ANC) of stream discharge can be understood in terms of evapotranspiration and proton uptake associated with nitrate and sulfate removal. Stream discharge ANC is strongly partitioned towards exported dissolved organic carbon, shifting the buffering intensity to lower pH compared to the groundwater. Given the extremely low alkalinity of the regional groundwater, these alpine peatlands likely have a critical role in increasing headwater stream buffering capacity.