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Issue: Catchment scale influences - Hydrological condition - Ecological aspects of river flow regimes

This is an issue under the Inland waters theme of the Data Reporting System.

Why we need to know about this issue

Ecosystems are the result of complex interactions between plants, animals and the physical and chemical characteristics of the environment, and they vary in type (e.g. floodplain wetlands and mountain streams) and with climatic conditions. Aquatic ecosystems are under pressure from the development of water resources for human use and activities in the catchments.

Modified river flows strongly influences inland aquatic ecosystem health. The natural flow regimes of many regulated river systems have been modified because of water extractions and the use of rivers as irrigation and water supply channels. Many of Australia’s native flora, fauna and habitats are dependent on natural flow regimes so changes in flow patterns have a significant effect. Aquatic ecosystems in the highly regulated river systems of the Murray—Darling Basin and a number of smaller eastern coastal river systems are likely to be under pressure from modification to natural flow regimes. River condition can impact on flow regimes and vice versa.

Indicators

• IW-10 Assessment of river condition indices 
  The component parts of this indicator provide a broad insight into the condition of river systems in respect to several aspects of flow regimes.
• IW-11 Number of licences dams, weirs, regulators and levees 
  A significant pressure on aquatic ecosystems has been artificial flow regimes as a result of diversion of water, channelisation of rivers, weirs and dams, construction of levee banks to reduce the land areas affected by low to moderate flooding, modification of natural drainage patterns, and vegetation clearing and grazing. Number of weirs and dam is a crude but direct measure of this pressure.
• IW-26 Forested streamlength 
  Riparian vegetation protects waterbodies from pollutants by filtering catchment runoff, reduces bank erosion, provides instream and bank habitats and provides food for biota.
  Although the indicator does not provide insight into the extent or condition of riparian vegetation, forested streamlength does provide a direct and measurable indication of how much of the length of Australian streams are protected by streamside vegetation, the streams, where it continues to be lost, where revegetation is occurring, and the rate at which the loss or revegetation is occurring.
• IW-27 Extent of significant wetlands (incl. Ramsar) 
  Although extent of wetlands is to some extent seasonal, long term trends in extent of wetlands is a surrogate indicator for condition of wetlands and both extent and condition of wetlands are in turn indicative of the ecology of river flow regimes.
• IW-28 Number of effective fishways 
  The construction of dams and weirs change the connectivity of aquatic systems. Fishways go someway in improving connectivity for fish. Number of effective fishways would be indicative of improvements in the management of this ecological aspect of river flow regimes.
• IW-44 Sustainable yield determination 
  The COAG principles include provisions for allocating water for the environment. Implementation of the COAG water reforms should enhance the ecological aspects of river flows. Monitoring of their implementation should provide critical indicators of the effectiveness of environmental flows allocation and management, and should ultimately result in improved hydrological and ecological condition of river systems.
• IW-46 Implementation of COAG principles 
  The COAG principles include provisions for allocating water for the environment. Implementation of the COAG water reforms should enhance the ecological aspects of river flows. Monitoring of their implementation should provide critical indicators of the effectiveness of environmental flows allocation and management, and should ultimately result in improved hydrological and ecological condition of river systems.

Related issues

• Inland Waters - Catchment scale influences- Hydrological condition- Surface-water availability and human use 
• Inland Waters - Catchment scale influences- Hydrological condition- Ground-water availability and human use 
• Inland Waters - Catchment scale influences- Hydrological condition- Connectivity - dams, weirs, regulators and levees 
• Inland Waters - Response of biota- Macroinvertebrates 
• Inland Waters - Habitat scale influences- In-stream habitat - woody debris and sand slugs