Longitudinal effects of a water supply reservoir (Tallowa Dam) on downstream water quality, substrate and riffle macroinvertebrate assemblages in the Shoalhaven River, Australia
Ivor Growns A D , Ivars Reinfelds B , Simon Williams B and Geoff Coade CA Department of Water and Energy, PO Box U245, Armidale, NSW 2351, Australia.
B Department of Water and Energy, PO Box 867, Wollongong East, NSW 2520, Australia.
C Department of Environment and Climate Change, PO Box A290, Sydney South, NSW 1232, Australia.
D Corresponding author. Email: ivor.growns@dnr.nsw.gov.au
Marine and Freshwater Research 60(6) 594-606 https://doi.org/10.1071/MF08144
Submitted: 2 May 2008 Accepted: 1 February 2009 Published: 19 June 2009
Abstract
Approximately 15% of the world’s total run-off is presently retained by more than 45 000 large dams. However, the extent of the downstream ecological impacts of those dams is rarely assessed. The longitudinal effects of a large reservoir on the substrate, water quality and riffle macroinvertebrate communities were examined between 0.5 and 18.3 km downstream of Tallowa Dam. The number of taxa and the Australian River Assessment Scheme observed v. expected score generally increased with increasing distance from the dam, average clast size decreased with increasing distance and water quality showed distinct longitudinal patterns. Classification of the macroinvertebrate assemblages identified two groups, one from riffles ~4 km downstream of the dam and one further downstream, suggesting the main impact occurs close to the dam. The difference between the two groups of riffles resulted mainly from the following macroinvertebrates, Edmundsiops (Baetidae), Hemigomphus (Gomphidae), Illiesoperla (Gripopterygidae), Physa (Physidae), Nannoplebia (Libellulidae) and Austrolimnius larvae (Elmidae), occurring less frequently in the near-dam riffles. Water quality was probably the main cause of the altered macroinvertebrate assemblage structure, not altered hydrology, a result attributable to the small operational capacity of Tallowa Dam relative to the annual inflow volumes.
Additional keywords: bioassessment, river regulation.
Acknowledgements
Peter Serov, Doug Westhorpe, Daryl Head, Chris Rush and Lisa Thurtell assisted with fieldwork. Colin Besley, Cathy Cunningham, Nathan Harrison, Dave Holleley and Mark Hopkins from Sydney Water Corporation are thanked for the identification of the macroinvertebrate samples. Tony Paull (Sydney Catchment Authority) provided the hydrological data. Peter Serov, Tony Paull, Maree Abood and Doug Rhodes commented on earlier drafts of this manuscript and comments from two anonymous referees were welcomed. This work was undertaken for the Shoalhaven Environmental Flows Scientific Advisory Panel for the Department of Natural Resources. Macroinvertebrate sampling was carried out under scientific research permit number P02/0021 issued by the Department of Primary Industries – Fisheries.
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