WetlandsIntroductionIn simple terms, wetlands may be defined as areas that are permanently or temporarily covered by fresh, brackish or saline water. Many names are used for wetlands, including lakes, swamps, bogs, fens, lagoons, creeks, corals, ox-bow lakes, marshes, and billabongs, a word that has become part of Australian folklore. Wetlands exhibit very great diversity in terms of size, depth of water, still or flowing water, duration of inundation, hydrologic connection with rivers, water quality, and vegetation. There are many types of wetlands, both natural and artificial, depending on their location, from those in the humid uplands of the Australian High Country to those in the semi-arid plains in the western parts of the Basin.
Wetlands in the MDBThe nature of the Murray-Darling Basin and its rivers, especially as they meander over the vast plains that make up most of the Basin, are major reason for the large number of wetlands. Their full extent is not known, though it is estimated that there are over 30,000 in the Basin, most of them on private land. Among the limited number of comprehensive surveys, a study along the River Murray indicated that from its mouth to Lake Hume, together with the anabranch system of the Edward and Wakool rivers, there are over 7,000 wetlands, covering over 222,000 hectares (Pressey 1986; Pressey 1990) (Table 1). Most are small, with 83 per cent being 10 hectares or less in extent, but there are 27 wetlands over 500 hectares in extent and these account for 36 per cent of the total wetlands area (Figure 1). Figure 1 Major Wetlands in the MDB
Large wetland systems occur along the Darling River and its tributaries (Kingsford et al. 1994). Some of these have suffered varying degrees of degradation and loss over recent years due to changes in flooding patterns and land uses. Examples include the Macquarie Marshes, the Narran Lake area, and the wetlands along the Lower Gwydir River and Gingham Watercourse. For the whole of Australia, 49 wetlands have now been recognised as being of international significance and are listed under the 1971 Convention on Wetlands of International Importance (the Ramsar Convention), which has now been signed by 92 countries (ANCA 1996, 15-30). Ten of these wetlands are in the MDB (Table 2 and Figure 1). The broad objectives of the Convention are to stem the loss of wetlands and ensure their conservation and wise use. The Ramsar listed wetlands are but a small part of the total number of wetlands in Australia. A Directory of Important Wetlands in Australia (ANCA 1996) lists nearly 700 locations, with a total area of over 24.2 million hectares. Many of these are in the Murray-Darling Basin. The larger ones are given in Table 3 and their locations are indicated on Figure 1. This is only a selection of the many thousands of wetlands in the Basin. A very much larger map would be required to show all of the wetlands.
Importance and functionsWhat are the functions of wetlands? Why are they so important? In brief, they are among the Basin's most productive and biologically diverse ecosystems. They provide essential breeding and feeding habitats for many kinds of organisms, waterbirds, fish, invertebrates, and plants (CRCFE 1995). Of particular value is their role in absorbing, recycling and releasing nutrients and trapping sediment. In other words, they are natural filters which improve water quality. At the same time, excessive pollutants will degrade or destroy wetlands. Wetlands also increase the productivity of associated aquatic and terrestrial ecosystems. Wetlands add to the diversity of the landscape and are a focus for a number of recreational activities. Given the Basin's generally dry but highly variable climate, the wetlands act as environmental buffer areas. During wet periods, they spread flood peaks and store floodwaters, releasing them gradually and thus mitigating the effects of flooding. During drought, they provide refuges for wildlife and grazing for stock (NSWWRC 1993; Sharley & Huggan 1994). An illustration of some of the economic values that can be placed on wetlands is provided in the discussion of the Barmah-Millewa Forest (see Forestry; also NSWDLWC 1996a, 13-16). As well as being included in the Ramsar list, these and a number of others are significant enough to be included in the Register of Australia's National Estate. Many of the Basin's wetlands are also recognised as important habitats and breeding grounds for migratory waterbird species. Australia is a signatory to certain international agreements, such as the 1974 Japan-Australia Migratory Birds Agreement (JAMBA) and the 1986 China-Australia Migratory Birds Agreement (CAMBA). Among other things, these agreements require that consideration be given to habitat conservation. The three countries are developing a Migratory Waterbird Conservation Strategy.
Threats to wetlandsAs with many aspects of the Basin's natural environment, human activities and their consequences continue to pose threats to the Basin's wetlands. The major problems are drainage, reduced river flows as a result of diversions, river flow regulation, livestock grazing, and exotic species such as carp (see Fisheries) and weeds (Table 4). River flow management is critical to maintaining the natural characteristics and health of the rivers and their wetlands. Of particular importance for many wetlands is periodic flooding, followed by a drying phase, as flooding triggers breeding and regeneration of riverine fauna and flora. Reservoirs and other storage structures have changed normal river flow patterns. While for some wetlands the problem is too much water, in most cases it is the changes to the river regimes, the reductions in flows and the elimination of small to medium-sized floods that have contributed to wetlands degradation (Table 5). "For example, prior to the regulation of the Gwydir River by Copeton Dam, wetlands were estimated to cover up to 47,000 hectares. The remnant wetland area is now 8,400 hectares and water fowl populations have been reduced significantly" (NSWWRC 1993, 38). Over the period 1944 to 1993, the Macquarie Marshes were reduced in area by 40 to 50 per cent (Kingsford & Thomas 1995). Along the Murray, some 37,000 hectares of wetlands have been destroyed or greatly modified by permanent inundation following the construction of weirs and other structures. These barriers maintain water at higher levels and for longer periods, often eliminating or significantly reducing the drying periods that are essential for the release of nutrients and accumulated detritus for input to the food chains. The changes to river regimes and watering patterns result in major changes to wetlands vegetation and consequently to food supplies for waterfowl and fish, resulting in reduced breeding. Livestock grazing is a particular problem in many wetland areas. Some areas have been drained and cleared for agricultural activities. Even where wetlands are not actually being eliminated, the effects of wetland degradation are numerous (Table 6). A number of wetlands have changed ecological character as a result of their use as evaporation basins for the disposal of saline drainage water from irrigation areas, as in the South Australian Riverland district and at Kerang. This keeps the wetlands more or less full of highly saline water, resulting in the destruction of virtually all flora and fauna in them and their surroundings. One such area, the Loveday Swamp, adjacent to the Cobdogla Irrigation Area, is now being rehabilitated by the South Australian Field and Game Association. Whilst many wetlands have been lost or degraded, new ones have been established through the many water storages that have been built within the Basin (see Water Use). This is also true for the drainage water disposal schemes that have been built, such as Tullakool and Noora, which was modified to provide for waterbird habitat. Managing the wetlands |
More recently, other studies have been completed, such as in the Namoi and Gwydir Vallets, along the Lower Darling and the New South Wales portion of the Parood River (King et al. 1995). The completion of other studies will provide a much more comprehensive picture of the Basin’s wetlands (Kingsford et al. 1997; Kingsford & Thomas 1997). To complement the responsibilities and activities of the relevant state authorities, the Murray-Darling Basin Commission has prepared a draft Floodplain Wetlands Management Strategy (MDBMC 1995). Its goal is -: Among other things, this recognises that the preservation, protection and management of floodplains or riparian zones and their wetlands are the key to protecting the health of the total riverine environment. Increasingly it is being recognised that the wetlands are vital importance to the Basin's total aquatic systems and everything that depends on its water resources, including the economic well-being of the Basin (see Floodplain Wetlands Management Strategy). While the MDBMC Strategy applies only to the floodplain wetlands of the Basin, these are by no means the only ones. |
| Also, whilst many of the wetlands are on public land and thus the responsibility of government agencies, many others are on private land and managed by the landholders. Increased attention is being given to joint management between the landholders and the government agencies responsible for reserves and wildlife.
In many situations, there is a need to identify the natural hydrologic characteristics of wetlands and reinstate a more natural hydrologic regime in their associated rivers. This may well require the allocation of water specifically for wetlands, as has been done in the case of the Macquarie Marshes (NSWDWR 1986) and the Barmah-Millewa Forest (MDBC 1992). Such measures are contentious, clearly having implications for other water users, as they may involve the re-allocation of water away from other existing uses. For example, a proposal for a significant increase in water allocations for the Gingham Watercourse wetlands, on the lower Gwydir River, and consequent reductions in allocations for irrigation has met with major opposition from cotton growers. A revised water management plan has been finalised for the Macquarie Marshes, a wetland system that covers some 200,000 hectares of which 18,150 hectares are in the Macquarie Marshes Nature Reserve, which is a Ramsar listed site. The plan involves increases in environmental flows for the Marshes, greater restrictions on access to unregulated flows for irrigation, and more controls on irrigation in the vicinity of the Marshes (NSWDLWC 1996b). Adequate management of the whole area is essential to maintaining the values of the small area included in the Nature Reserve. Such measures have to be put in the context of the increase in the irrigated area along the Macquarie River from 17,500 hectares in 1965 to 85,580 hectares in 1990. It is now increasingly recognised that the use and management of the Basin's floodplains and riverine areas require much greater co-ordination, especially where more than one jurisdiction is involved. A good illustration is provided from the River Murray by Guidelines for the Preparation of River Management Plans (MREP 1995), which set out the planning principles for the riverine lands along the Murray from the Hume Dam to the South Australian border.
Case StudiesThe Chowilla Floodplain Located near Renmark, the Chowilla floodplain covers 17,700 hectares, of which three-quarters is in South Australia and the remainder in New South Wales, essentially on the northern side of the River Murray (Phillips & Sharley 1993; Sharley & Huggan 1995). It is a wetland in an arid environment, totally dependent on the Murray. It contains a diversity of habitats, with lakes, billabongs, islands, flowing creeks, levees and lunettes, and more than 100 km of anabranch creeks. About 30,600 hectares of the Chowilla Floodplain in South Australia constitute the 'Riverland' Wetland Complex which was listed under the Ramsar Convention in 1987 (ANCA 1996, 494-496). The natural environment has been affected by many factors, including a long history of livestock grazing, cutting timber to fuel river boats and the Renmark irrigation pumps, and the construction in 1930 of Lock 6 on the River Murray. The Lock resulted in permanently higher water levels on the floodplain and continuous flows of water through the Chowilla anabranch system. The area is one of natural discharge of saline groundwater (some of it as salty as seawater), but the salinity problems have been exacerbated by the higher groundwater levels resulting from Lock 6. Among other things, river regulation has resulted in a reduction of flood frequency, significantly reducing the flushing of salt from the floodplain. This has affected the vegetation and resulted in the death of many trees, including the salt-tolerant black box. In spite of the changes, the Chowilla Floodplain is one of the last parts of the lower Murray floodplain that has not been used for irrigation and it retains much of the area's natural character and attributes. On it stands the largest remaining area of natural riverine forest, especially river red gums (Eucalyptus camaldulensis), in the lower Murray valley. It is home for a number of threatened species of both flora and fauna, just some of the area’s more than 300 species of vertebrate animals, including over 200 birds, as well as mammals, reptiles, frogs and fish. It is also an important area for recreation, sheep grazing, and fishing, both commercial and recreational. Following a period of consultation between the Murray-Darling Basin Commission, the relevant departments from both state governments, and the community, the Chowilla Resource Management Plan was adopted (Sharley & Huggan 1995). This is an integrated plan that is sympathetic to the requirements of the commercial and recreational users and which, at the same time, aims to protect and restore the natural ecological features of the Chowilla Anabranch system. Among the major issues addressed by the plan are salinity mitigation, land degradation, recreation management, wetland management and land tenure (Table 7). However, given that high levels of saline groundwater are maintained by the presence of Lock 6, it will be some years before the mitigation measures make any positive impact. The Chowilla floodplain is part of the Bookmark Biosphere Reserve, which covers over 600,000 hectares to the north of the Murray in South Australia’s Riverland, and is part of the network of international Biosphere Reserves co-ordinated by the UNESCO ‘Man and the Biosphere’ Program. A community based group, now called the Bookmark Biosphere Trust, is responsible for the implementation of the Chowilla plan and the management of the Reserve (Wetlands Australia, Issue 2, 1995, 6-7). Narran Lakes The Narran Lakes and swamps cover a total area of some 10,000 hectares east of Brewarrina in northern NSW. They form the terminal drainage basin of the Narran River, a distributary of the Balonne River. When full, Narran Lake is one of the largest freshwater lakes in the state. Located in a semi-arid region, the area floods after heavy rain in the headwaters of the river system in southern Queensland. This occurs about once every two to five years. After flooding, water may persist in the lake for up to two years. The swamps are vegetated with dense lignum, together with river cooba (Acacia stenophylla) and coolibah (Eucalyptus microtheca) along the river banks, while the lakes are bordered with annual saltbush and copperburrs. Following flooding, there is a large influx of waterbirds to the area, and many species breed. Very large nesting colonies of straw-necked ibis (Threskiornis spinicollis) sometimes occur in the swamps. Large concentrations of ducks occur on the lake as water recedes, as well as pelicans and black swans (ANCA 1996, 58-59; Brooker 1993). Narran Lakes and the associated wetlands remain in relatively natural condition, and are thus representative of the large terminal drainage wetlands which occur in semi-arid NSW. However, over recent years, together with wetlands upstream in both New South Wales and Queensland, the area has come under serious threat as a result of water extraction developments in Queensland, primarily for cotton growing. Of particular significance are developments on Cubbie Station, located where the Balonne divides to form the Culgoa, Birrie and Narran Rivers. The consequent reduced flows and the loss of small to medium size flood flows have already affected the wetlands and the use of the area, in the dry phases following flooding, for grazing. This is a further illustration of the importance of beneficial flooding and the losses that occur when it is eliminated. It is also an issue for consideration by the Border Rivers Commission which is responsible for the rivers that cross from Queensland into New South Wales. Ginini Flats Sub-Alpine Bog Complex, Namadgi National Park, ACT Located in the upper catchment of the Cotter River at an altitude of over 1,500 metres, the Ginini Flats is an area of sub-alpine bogs and wet heath and grasslands (ANCA 1996, 35-36). There are some 50 hectares of wetlands and 75 hectares of open flats. The Ginini Flats Sub-Alpine Bog Complex is one of the most recent additions to Australia's list of Ramsar sites. The impeded drainage has contributed to the formation of extensive Sphagnum bogs on deep peaty soils. The area is at the northern limit in the Australian Alps for such vegetation, but includes some of the largest, deepest and best preserved Sphagnum bogs on the Australian mainland. The Flats provide important breeding habitat for a number of rare fauna, in particular, one of the largest known populations of the threatened corroberee frog (Pseudophryne corroboree (Nv)). Wakool-Tullakool Evaporation Basins Whilst human activity has resulted in the loss of many wetland areas, it has also added new ones, including the many water storages (from farm dams to major reservoirs) and, more recently, the evaporation basins that have been established for the disposal of saline drainage and groundwater. An example of the latter are the evaporation basins built in the 1980s for disposing of saline groundwater from the Wakool and Tullakool districts of Murray Irrigation (see Irrigation). They cover an area of some 2,100 hectares and are among the largest their kind in Australia. The salinity levels increase as the water moves through the evaporation bays making habitats suited to different plant species, depending on their salt tolerance. Up to 60 species of waterfowl have been recorded in the basins, including migratory species. Over 20,000 ducks at a time have been reported on the basins, while in 1991 several hundred freckled duck (Stictonetta naevosa) were observed (ANCA 1996, 82-83).
ConclusionThe importance and functions of wetlands are only now becoming fully appreciated (McComb & Lake 1990). As the recent Audit of Water in the Murray-Darling Basin has stated:
Healthy river systems are the basis for sustainable long-term use for all users. But wetlands are of importance and value for much more. After many years of destroying and degrading wetlands,"We are now beginning to understand how valuable these areas are for environmental, economic and social reasons" (ANCA 1996, 1).
References ANCA(1996): A Directory of Important Wetlands in Australia. Second edition. Australian Nature Conservation Agency, Canberra. Brooker, M.G. (1993): "Aerial counts of waterbirds on Narran Lake, NSW". Australian Bird Watcher, 15, 13-18. CRCFE (1995): Billabongs, Floodplains and River Health. Cooperative Research Centre for Freshwater Ecology, Albury. King, A.M. et al. (1995): Wetlands of the Paroo River and Cuttaburra Creek. Technical Services Division, NSW Department of Land and Water Conservation, Sydney. Kingsford, R.T. & Thomas, R.F. (1995): "The Macquarie Marshes in arid Australia and their waterbirds: a 50-year history of decline". Environmental Management, 19, 867-878. Kingsford, R.T. & Thomas, R.F. (1997): "A GIS for wetlands of the Murray-Darling Basin". Wetlands Australia, 7, 8. Kingsford, R.T. et al. (1994): Waterbirds and Wetlands in Northwestern New South Wales. Occasional Paper No. 19. NSW National Parks And Wildlife Service, Sydney. Kingsford, R.T. et al. (1997): Significant Wetlands for Waterbirds in the Murray-Darling Basin. NSW National Parks And Wildlife Service, Sydney. McComb, A.J. & Lake, P.S. (1990): Australian Wetlands. Angus & Robertson Books, Sydney. MDBC (1992): Watering the Barmah-Millewa Red Gum Forest: issues paper. Murray-Darling Basin Commission, Canberra. MDBMC (1995a): Floodplain Wetlands Management Strategy for the Murray-Darling Basin. Murray-Darling Basin Ministerial Council, Canberra. MDBMC (1995b): An Audit of Water Use in the Murray-Darling Basin. Murray-Darling Basin Ministerial Council, Canberra. MREP (1995): Guidelines for the Preparation of River Management Plans under Murray Regional Environmental Plan No.2 - Riverine Land. Murray-Darling Basin Commission, Canberra. NSWDLWC (1996a): The NSW Wetlands Management Policy. New South Wales Government, Sydney. NSWDLWC (1996b): Macquarie Marshes Water Management Plan 1996. NSW Department of Land and Water Conservation, Orange/NSW National Parks and Wildlife Service, Sydney. NSWDWR (1986): Water Management Plan for the Macquarie Marshes. Department of Water Resources/National Parks and Wildlife Service, Sydney. NSWWRC (1993): Our Water: a review of the current status of the water resources of New South Wales and the key issues relevant to their future development. NSW Water Resources Council, Sydney. Phillips, B. & Sharley, T. (1993): "The Chowilla management plan, Australia". pp. 64-73 in Towards the Wise Use of Wetlands: report of the Ramsar Convention Wise Use Project, edited by T.J. Davis. Ramsar Convention Bureau, Gland, Switzerland. Pressey, R.L. (1986): Wetlands of the River Murray below Lake Hume. River Murray Commission, Canberra. Pressey, R.L. (1990): "Wetlands". pp. 166-181 in The Murray, edited by N. McKay and D. Eastburn. Murray-Darling Basin Commission, Canberra. Sharley, T. & Huggan, C. (Editors)(1994): Murray-Darling Basin Floodplain Wetlands Management: proceedings of the Floodplain Wetlands Management Workshop, Albury NSW 20-22 October 1992. Murray-Darling Basin Commission, Canberra. Sharley, T. & Huggan. C. (Editors)(1995): Chowilla Resource Management Plan: final report. Murray-Darling Basin Commission, Canberra.
Table 1 Wetlands along the Murray and Edward Rivers* (source: Pressey 1986)
* From Lake Hume to the mouth of the Murray ** Includes Lakes Alexandrina (64,950 ha) and Albert (17,310 ha) and the Coorong (22,530 ha), net for South Australia 33,500 ha.
Table 2 Wetlands in the Murray-Darling Basin that are of International Importance and listed under the Ramsar Convention (source: ANCA 1996)
* The full extent of the Macquarie Marshes is some 200,000 hectares.
Table 3 Important wetlands of 5,000 hectares or more in extent (source: ANCA 1996)
(excluding the Ramsar sites)
Table 4 The main causes of floodplain wetland degradation (source: MDBMC 1995a, 12)
Table 5 Summary of wetland reduction indicating the recent condition of floodplain wetlands in the Murray-Darling Basin (source: MDBMC 1995a, 10-11)
NB: Some of the above figures are open to question.
Table 6 Summary of the main effects of wetland degradation (source: MDBMC 1995a, 13)
Table 7 Key features of the Chowilla Resource Management Plan (source: Sharley & Huggan 1995, 25)
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