Australia State of the Environment Report 2001 (Theme Report)
Prepared by: Jonas Ball, Sinclair Knight Merz Pty Limited, Authors
Published by CSIRO on behalf of the Department of the Environment and Heritage, 2001
ISBN 0 643 06750 7
Aquatic ecosystems (continued)
Protecting, restoring and managing aquatic ecosystems (continued)
The importance of managing and restoring riparian vegetation is now well recognised, and remedial work is being undertaken at the local, regional, state and national level. Catchment and Landcare groups, for example, recognise that environmental and agricultural objectives can be achieved simultaneously. Riparian revegetation is widely accepted as an affordable and effective means of erosion control and bank stabilisation in many catchments. The actions of these groups at the local level are contributing significantly to the restoration of riparian vegetation along many of Australia's waterways.
Although most states and territories do not have specific legislation for managing riparian zones, other legislation focused on land-use planning, native vegetation protection and the regulation of pastoral lands and Crown land can apply to riparian environments (Cripps 1999). Legislation such as the Flora and Fauna Guarantee Act 1994 in Victoria lists the clearance of riparian vegetation as a threatening process.
Case study 14: The Australian Arid Zone Rivers project
The Australian Arid Zone Rivers project (ARIDFLO) is a three-year multi-disciplinary research project on selected rivers of the Lake Eyre Basin (Figure 34) and aims to develop an interactive predictive model of hydrology-biology relationships for Australian arid zone rivers. Arid zone rivers are hydrologically, biologically and geomorphologically different from rivers in other zones of Australia. Hydrologically they are more variable, their geomorphology is less stable, and many of their plants and animals are more opportunistic (Puckridge et al. 2001). For these reasons it is essential that management of such rivers is based on specific local information, and does not attempt to extrapolate from findings in rivers in wetter environments.
The ARIDFLO model will provide input into determining environmental flow requirements of Australian arid zone rivers, as well as helping to predict the impacts of upstream water developments on aquatic biota.
Data are already providing important knowledge on arid riverine flow requirements. The year 2000 brought the biggest floods in the Lake Eyre Basin since 1990, enabling ARIDFLO to capture biological responses to a wide spectrum of short-term events. Analysis indicated that for flow pulses with total flow volumes at Diamantina Lakes of less than 1.2 GL, between 75-94% of the total flow volume did not arrive at the downstream gauging station at Birdsville (Puckridge et al. 2001).
Research has highlighted that the Lake Eyre Basin fish communities are unusually responsive to hydrological events as larvae and young juveniles of bony herring, desert rainbowfish and the Lake Eyre hardyhead were abundant following flooding (Puckridge et al. 2001). Large-scale geomorphological features - tributary junctions and river bends - were found to be crucial in providing sufficient water-residence time for the large colonial nesting birds to complete a successful breeding cycle (Puckridge et al. 2001).
The ARIDFLO model will be available as a predictive modelling tool in the assessment, management and monitoring of water use projects in the arid zones, and in the restoration of arid zone rivers already affected by water resource use.
A number of different demonstration and evaluation projects are being run across Australia to examine riparian vegetation management. These projects cover a wide variety of issues such as streambank stability, salinity, vegetation establishment, weed control, native plant regeneration and stock management.
The National Land and Water Resources Audit (NLWRA) assessed the availability of riverine vegetation data from the states and territories (LWRRDC 2000). While most have undertaken some riparian mapping, they only provide a snapshot of riparian zone condition and extent and do not allow an analysis of change in riparian extent. The NLWRA proposes building upon the National Vegetation Information System (NVIS) to provide a future benchmark for measuring riparian vegetation losses.
The National Riparian Zone Program managed by Land and Water Australia aims to clarify how fringing vegetation, sedimentation and eutrophication interrelate, and how the health of downstream waterways is affected by the health of fringing vegetation. The program has been successful in producing scientifically based guidelines for riparian management which are supported by technical manuals.
Experimental and demonstration/evaluation sites around Australia are helping to improve community understanding of the interactions between riparian lands and adjacent waterbodies. Research is currently being undertaken in the Johnston River, Mary River and Coopers Creek in Queensland, in the Bega and Clarence rivers in New South Wales, in the Goulburn-Broken catchment in Victoria, in the Midlands and Buckland rivers in Tasmania, in the Mount Lofty Ranges in South Australia and in the Kalgan and Blackwood catchments in Western Australia (Askey-Doran et al. 1999).
To date the project in the Mary River has resulted in positive outcomes for riparian vegetation. Three experimental planting sites have been developed to demonstrate cost-effective methods of riparian rehabilitation. Stock exclusion during the establishment phase of the planting sites was an important management action to assist in rehabilitation. Results after two years indicate that biodiversity was high, with 74 different species becoming established on the site (Stockwell 1999). After five years the site has an average canopy cover of 100% over the 560 m long by 25 m wide area replanted (Stockwell 1999). These results highlight the success of rehabilitation, although specific data on the benefits to aquatic ecosystem as a result of rehabilitation activities are yet to be determined.
Resnagging of rivers where feasible and practical is increasingly becoming a priority for the rehabilitation of aquatic ecosystems and specifically for native fish populations. A project is currently under way to resnag a reach of the Murray River in a phased approach with the aim of answering many immediate questions that arise from resnagging a river. Specific aims include:
- an objective basis for assessing the need for, and probable response to, river rehabilitation through resnagging
- practical techniques for resnagging and fish habitat rehabilitation
- snag design and practical management options for individual species and fish community rehabilitation
- adoption of scientifically based on-ground resnagging works in rivers providing improved habitat viability for native fish populations.
The results of this project will have important, positive benefits for understanding and demonstrating the value of resnagging of waterways throughout Australia.