State of the Environment

2006

Indicator: BD-14 Examples of impacts of changed hydrology on biodiversity

Data

Remnant vegetation and plantation forest at risk from dryland salinity (ha)
State Current 2020 Prediction 2050 Prediction
New South Wales 7 000 32 700 81 000
Victoria 6 000 11 800 24 300
Queensland not assessed not assessed 92 000
South Australia 18 000 22 000 25 000
Western Australia 600 000 710 000 1 800 000
Total 631 000 776 500 2 022 300

Source: National Land and WaterResources Audit 2005, Australian Dryland Salinity Assessment, viewed 6 Oct 2005, http://audit.ea.gov.au/ANRA/land/docs/national/Salinity_AUS.html

Examples of River Murray environmental flow management actions
Environmental Flow action Successful implementation? Scientifically demonstrated improvement in river health?
In-channel variation of flow Applied on the upper and lower river system Demonstrated ecological benefit on the Mitta Mitta River.
Wetland watering through delivering allocations, and enhancing natural floods Applied on private and public wetlands. Environmental allocations achieved. Demonstrated ecological benefit on private wetlands within the MIL area, the Barmah-Millewa Forest, Moira Lake, Werai Forest, Wanganella Swamp, and Victorian Murray wetlands.
Restoration of wetland hydrological regime using local structural and operational manipulation Applied on Moira Lake and SA Riverland wetlands Demonstrated short-term ecological benefits; overall long-term improvements in ecological health not yet evaluated.
Flows to disperse blue-green algae Applied on lower Murray and Darling Rivers Some limited evidence of ecological benefit.
Weir pool drawdown Applied from time to time for maintenance at several weirs, and annually for environmental reasons on Stevens Weir; some resistance to experimental environmental drawdown elsewhere Salinity impacts within tolerable range at Mildura for short drawdown. Salinity impacts may be significant if river flows are low or if drawdown is for an extended period. Ecological benefits not yet demonstrated at Mildura Weir or at Stevens Weir
Weir pool surcharging associated with flood enhancement Applied on the lower River Murray (Lock 5) Demonstrated ecological benefit
Sediment flushing flows Applied at the Murray Mouth Applied flow insufficient capacity, so sediment flushing not yet demonstrated
Mimic shape of natural hydrographs Applied on the lower Darling River Not monitored.
Temporarily open weir gates to allow fish passage Applied at Torrumbarry Weir and Stevens Weir Open passage demonstrated; overall significance to fish movement not measured

Source: Gippel, C 2003, Review of achievements and outcomes of environmental flow initiatives undertaken on the extended River Murray System to August 2002, Fluvial Systems Pty Ltd, Canberra, viewed N/A, http://www.thelivingmurray.mdbc.gov.au/reports.

Number of nationally important wetlands and number with threatened water regimes
No. of Sites (C'wealth owned or managed) Number of wetlands with threatened water regimes*
Australian Capital Territory 13 (0) 4
New South Wales 178 (6) 38
Northern Territory 33 (4) 7
Queensland 181 (8) 42
South Australia 69 (1) 19
Tasmania 89 (0) 13
Victoria 159 (4) 57
Western Australia 120 (8) 51
External Territories 9 (9)
Total 851 (40)

Source: Environment Australia 2001, A Directory of Important Wetlands in Australia Third Edition, Environment Australia, Canberra, viewed N/A, http://www.deh.gov.au/water/wetlands/database/directory/index.html.

*Source: Davis, JA, Froend, RH, Hamilton, DP, Horwitz, P, McComb, AJ, Oldham, CE 2001, Environmental Water Requirements to Maintain Wetlands of National and International Importance, Commonwealth of Australia,, Canberra, viewed N/A, http://www.deh.gov.au/water/rivers/nrhp/wetlands/pubs/wetlands.pdf.

Threats include: change in drainage due to peat moss extraction, walkers, cattle and sheep trampling, channels dug for sheep watering holes, drainage, irrigation, sedimentation, water diversion, river regulation, levees, dams and weirs, water storage, mining, saltwater intrusion, groundwater extraction, prolonged inundation (tree deaths), potentially changed flooding regimes due to clearing for horticulture/mixed farming, siltation through overgrazing, aquifer draw down caused by water harvesting from the Great Artesian Basin, road and drain construction, tourist and recreational development, altered hydrology to prevent tidal intrusion, road crossing, urban expansion, discharge from sewerage treatment plant, and disposal of saline groundwater.

Ninety percent of floodplain wetlands in the Murray-Darling Basin, 50% of coastal wetlands in New South Wales and 75% of wetlands on the Swan Coastal Plain in south-west Western Australia have been lost due to altered flow regimes.

Regulated river reaches below hydroelectric dams with rapid diurnal changes in flow and erratic flow patterns are typically characterised by low diversity macro-invertebrate communities. Sudden increases in flow can cause catastrophic downstream drift to the extent that as much as 14% of the biomass of benthic biota is lost.

Source: Arthington, A H 2002, unpublished data, Environmental flows: ecological importance, methods and lessons from Australia, viewed 4 Oct 2005, http://www.mekong.es.usyd.edu.au/events/
past/Conference2002/angela_arthington.pdf.

What the data mean

Many wetlands are threatened by a range of hydrology issues. Predictions indicate that the impact of dryland salinity will become much more severe, with serious consequences for biodiversity.

Examples of River Murray environmental flow management actions indicate that some efforts are being made to reverse the effects of altered environmental flows.

Data Limitations

Data has not been updated since the NLWRA

Issues for which this is an indicator and why

Biodiversity — Pressures on biodiversity - Changed hydrology 

In the absence of comprehensive data on the impacts of changes in hydrology on biodiversity, some examples of the impacts on particular species, and on particular places where species are likely to be vulnerable, provide insights into this pressure.

Other indicators for this issue:

Land — Land condition - Hydrology 

Changes in hydrology impact on the land both directly and indirectly via their impact on terrestrial species.

Other indicators for this issue:

Inland Waters — Habitat scale influences - Wetlands 

Development in many areas has resulted in reduced overland and groundwater flow to wetlands, causing dry conditions. In the absence of comprehensive data on the impacts of changes in hydrology on wetland biodiversity, some examples of impacts of changed hydrology on wetlands affected are provided.

Other indicators for this issue:

Further Information

Salinity & biodiversity credits

Key

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