Natural and post-European settlement variability in water quality of the lower Snowy River floodplain, eastern Victoria, Australia

Abstract

Millennial to decadal resolution palaeoenvironmental records from the terminal floodplain lakes of the lower Snowy River in eastern Victoria have been obtained to determine the water quality history of the lower Snowy River floodplain and more specifically, the ecological impact of the inter-basin diversion of water from one of Australia's hallmark river systems. Lake Curlip, as evidenced through variations in the fossil-diatom flora, has evolved through the Holocene from a saline (17–22 g salt/l) open system (c. 7000 years BP) as sea levels reached their maxima, to a brackish (5–10 g/l), and then a fresh (as low as 0.4 g/l), possibly acidic system prior to European settlement (c. 300 years BP). The upper post-European sediments reveal a complex, highly variable, anthropogenically induced shift to a brackish and nutrient-tolerant diatom flora, with recent diatom-inferred salinities in the order of 20 g/l. Explained as a combination of land clearance, drainage practices, and more recently, the regulation of the Snowy River, recent changes are as pronounced as any experienced through the Holocene, but have occurred at a rate faster than any brought on by past climatic or geomorphic change. By quantifying the limnological changes before and after regulation this study informs on the relative benefits that may accrue from allocating environmental flows to the Snowy River. Copyright © 2005 John Wiley & Sons, Ltd.