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

- MacGregor, Angus, Gell, Peter, Wallbrink, Peter, Hancock, Gary

  • Authors: MacGregor, Angus , Gell, Peter , Wallbrink, Peter , Hancock, Gary
  • Date: 2005
  • Type: Journal article
  • Relation: River Research and Applications Vol. 21, no. 2-3 (2005), p. 201-213
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  • Description: 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.

Importance of environmental flows in the Wimmera catchment, Southeast Australia

- Atazadeh, Ehsan, Barton, Andrew, Razeghi, Jafar

  • Authors: Atazadeh, Ehsan , Barton, Andrew , Razeghi, Jafar
  • Date: 2021
  • Type: Text , Journal article
  • Relation: Limnological Review Vol. 20, no. 4 (2021), p. 185-198
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  • Description: In this paper the environment, climate, vegetation, indigenous and European settlement history, stream flow patterns, water quality and water resources development in western Victoria, Australia are studied. The last part of the paper focuses on the MacKenzie River, a tributary of the Wimmera River located on the northern slopes of the Grampians Ranges in western Victoria, Australia. Water release along the MacKenzie River was regulated to improve water quality, stream condition and river health especially in the downstream reaches. The upstream section tends to receive water most days of the year due to releases to secure the requirements of water supply for the city of Horsham and its recreational and conservation values, which is diverted into Mt Zero Channel. Below this the middle and downstream sections receive a more intermittent supply. Annually, a total of 10,000 dam3 of water is released from Wartook Reservoir into the MacKenzie River. Of this volume, only about 4,000 dam3 was released explicitly for environmental purposes. The remaining 6,000 dam3 was released to meet consumptive demands and to transfer water to downstream reservoirs. The empirical data and models showed the lower reaches of the river to be in poor condition under low flows, but this condition improved under flows of 35 dam3 per day, as indicated. The results are presented to tailor discharge and duration of the river flows by amalgamation of consumptive and environmental flows to improve the condition of the stream, thereby supplementing the flows dedicated to environmental outcomes. Ultimately the findings can be used by management to configure consumptive flows that would enhance the ecological condition of the MacKenzie River. © 2020 Ehsan Atazadeh et al., published by Sciendo 2020.

Restoring Murray River floodplain wetlands : does the sediment record inform on watering regime?

- Gell, Peter

  • Authors: Gell, Peter
  • Date: 2020
  • Type: Text , Conference paper
  • Relation: River Research and Applications Vol. 36, p. 620-629
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  • Description: The floodplain wetlands of the southern Murray Darling Basin (MDB) have been subject to the impacts of catchment and water resource development for more than a century. Their current degraded state is attributed to the regulation of the rivers and abstraction of water volume for irrigation. The MDB Plan is to return at least 2,750 Gl of mean annual flow to the system to restore the condition of waterways. Considerable recent investment in infrastructure enables water to be released into the basin's floodplain wetlands. The proposed watering regime is underpinned by modelling that suggests that, before regulation, overbank flows would have occurred regularly as discharge peaked in winter and spring. Sediment cores have been extracted from over 50 floodplain wetlands of the southern Murray Basin. Those from several, large meander wavelength billabongs extend for 1,000–5,000 years suggesting that these sites were permanently inundated over that time. Others extend to ~200 years and are presumed not to have accumulated sediment until more recently. The records of most wetlands, however, only extend to the onset of river regulation in the 1920s, suggesting that before then they were not inundated for sufficient duration for net accumulation to occur. Preserved diatoms suggest that the shallow, plant-dominated wetlands of the past have transitioned to deep, turbid water systems today. As rivers are identified as a source of sediment to wetlands, less regular inundation, rather than more, is a viable option in restoring the ecological function of these floodplain wetlands and in slowing sediment infill. © 2019 John Wiley & Sons, Ltd.
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