Alteration to the natural flow regimes of rivers and streams and their floodplains and wetlands was listed as a KEY THREATENING PROCESS on Schedule 3 of the Threatened Species Conservation Act 1995 [31 May 2002].
Alteration to natural flow regimes refers to reducing or increasing flows, altering seasonality of flows, changing the frequency, duration, magnitude, timing, predictability and variability of flow events, altering surface and subsurface water levels and changing the rate of rise or fall of water levels. Three human processes have predominantly altered flows in streams, rivers and their floodplains, and wetlands in NSW. These are: building of dams, diversion of flows by structures or extraction, and alteration of flows on floodplains with levees and structures.
Alteration to the natural flow regimes of rivers and streams and their floodplains and wetlands is recognised as a major factor contributing to loss of biological diversity and ecological function in aquatic ecosystems, including floodplains. These alterations could cause a large number of species, populations or ecological communities that rely on river flows for their short term and long term survival to become threatened. Impacts associated with altering natural flow regimes, include:
- extraction of water which reduces flows, leading to a lower distribution of organic matter on which invertebrates and vertebrates depend on;
- the permanent flooding of wetlands which kills vegetation depending on intermittent flooding, decreasing habitat for invertebrates and waterbirds as a result;
- riparian zone degradation where changes to flows increases erosion, leading to sedimentation impacts upon aquatic communities;
- deeper and more permanent standing water which permits the establishment and spread of exotic species; and
- changes to the physical, chemical and biological conditions of rivers and streams which alters biota.
Alteration to the natural flow regimes of rivers and streams and their floodplains and wetlands has been identified as a threat to a number of threatened species and communities. Habitat loss through altered hydrology patterns in rivers and wetlands has been identified as a threat for the endangered Spotted Tree Frog and the vulnerable birds, Blue-billed Duck and the Freckled Duck.
A related process, The installation and operation of instream structures and other mechanisms that alter natural flow regimes of rivers and streams is listed as a key threatening process under the Fisheries Management Act 1994.
A Saving Our Species conservation project is currently being developed for this species and will be available soon. For information on how you can contribute to this species' recovery, see the Activities to assist this species section below.