Water

Aside from its value as a vital and biodiverse habitat, the Barmah-Millewa system plays a variety of roles in improving river health and water quality, performing ecological services important to humans. As a natural floodplain, it is important for flood mitigation, protecting agricultural lands downstream from floods (Dexter 1979; Forests Commission Victoria 1983; State Working Group on River Murray Water and Forest Management 1984; MDBC 1998). The floodplain also filters salts, sediments and nutrients from the Murray water, improving water quality by removing nitrogen- and phosphorous-based nutrient compounds from the river water (Leitch 1989; McKinnon 1997; MDBC 1998) and thus reducing the probability of algal blooms occurring in the Murray (Robertson 1998). Floodplain vegetation and soils assist in the filtration of water to remove sediments (MDBC 1998), salts (Allen 1979) and organic carbon (Robertson et al 1999) thus improving water quality for downstream users.

In the forest/wetland complex of Barmah-Millewa the water table is approximately 11-14 metres below the surface, compared to an average of about 2 metres in the surrounding lands. This suggests that the forest also plays an important role in buffering against saline recharge waters entering agricultural lands and the river.

‘We are a water-based people whose very survival depends on the river systems that provide us with an abundance of fresh water food sources. The extensive evidence of middens and mounds (camp sites) and fish-trap systems that were constructed across the entrances of the river offshoots, are the tangible signs of Yorta Yorta reliance on water for our everyday livelihood. In addition, the oral knowledge from Yorta Yorta people of where and how our ancestors camped, fished and collected food from the waterways, indicates that just about everything was happening on, in and around the waters.’ (YYCG, 1999).

Acronyms:
UNESCO – United Nations Educational, Scientific and Cultural Organisation
JAMBA – Japan Australia Migratory Bird Agreement
CAMBA – China Australia Migratory Bird Agreement

THREATS

REGULATION OF WATER FLOWS

For the Barmah-Millewa ecosystem to thrive, it is dependant on a natural flooding regime. Regulation of these water flows has resulted in changes to the natural flooding cycles of Barmah-Millewa, with a marked overall reduction in the frequency and duration of flooding.

Natural Water Flows

Before European colonisation, the Barmah-Millewa forests would flood almost every year between August and December as rain and snow melt increased, followed by a dry period through summer until the following winter. When the river was in flood, water was forced into the forest, and the floodwaters were so plentiful that they allowed the growth of red gum to heights of 45 metres, where elsewhere the species grows only to around 12 metres.

The flood regime was responsible for maintaining ecosystem diversity in Barmah-Millewa. The exact timing, duration and depth of natural inundations varied slightly across the landscape, so that where the floods were too deep and/or too long for red gum seedlings to survive, grass plains formed, dominated by Moira Grass (Pseudoraphis spinescens). Moira grasslands were the first to flood each year and the last to recede (Ward 1991). The wet-dry cycles also maintained diversity within backwaters, billabongs, lagoons, marshes and swamps which filled and dried with the river level (Briggs et al 1997). The natural flooding regime is believed by scientists to have played an important role in maintaining populations of native fish in Barmah-Millewa. Frogs also relied on the natural flooding regime to provide a plentiful food supply and dense cover in rushland vegetation. Many waterbirds were also dependent on the flood regime to breed successfully, as the floods brought an increase in food.

Regulation of Water Flows

Over the years, the construction of a series of dams, weirs, levees, block banks and regulators along the Murray for irrigation has dramatically changed the way that water flows through the Barmah-Millewa forest. The forest is now flooded less frequently, for much shorter periods of time and over far a smaller area. The timing of floods has also changed as a result of water regulation, with winter floods being now less common than they used to be, spring floods less reliable, and summer floods becoming more common.

River red gums have taken over more than half the former area of the Moira grass plains in just 50 years, threatening them with extinction by 2050 if no action is taken (Ward, 1991). The health of red gum stands themselves has declined because of decreased flooding (Kingsford, 2000). On the other hand, summer floods have caused widespread tree deaths by turning semi-permanent wetlands into permanent wetlands (Briggs et al., 1997).

The water level in the intricate network of billabongs, backwaters, lagoons, marshes and swamps in Barmah-Millewa used to rise and fall with the water level of the mass flow of the river; this meant that many of these water bodies, including the broad shallow lakes, would dry out every year (Briggs et al., 1997). Now the shallow lakes rarely dry out: this has allowed large numbers of pest fish, such as carp, which compete with native fish and frogs for food and space to build up in the system. Simultaneously, the lack of large-scale floods has hindered the breeding capabilities of native fish species, many of which have now seriously declined in numbers (McKinnon, 1997).

The forest wetlands are a significant habitat and breeding grounds for waterbirds – around 54 species have been recorded breeding there. At least 10 of these species are recognized as being vulnerable, endangered or critically endangered. Water regulation has been identified as a major factor reducing the population sizes of breeding waterbirds over the past sixty years (Leslie, 2001). It is also believed to be at least partially responsible for the current low numbers of frogs found in the forest (Healey et al., 1997). The lack of floods on top of levee banks and at the margins of the forest has allowed the invasion of environmental weeds, which are usually killed by regular inundation (Ward, 1991).

The Living Murray Initiative has named Barmah-Millewa as one of six icon sites to be targeted for improving the health of the Murray River. As a ‘First Step Response’ the Council of Australian Governments have pledged $500 million and 500 billion litres of water for environmental flows. And yet, the forest wetlands are managed primarily as state forest, meaning that they are systematically being degraded by logging and cattle grazing.

A healthy forest is imperative for a healthy river. Environmental flows must be restored in order to ensure the survival of Moira grasslands, red gum tree, native fish and migratory water birds, and to control pest fish populations.

Friends of the Earth recommends the following action:

• That environmental flows which mimic the pre-1788 flood regime as closely as possible are to be allocated to Barmah-Millewa.

Further information, references and details on the more specific recommendations made by Friends of the Earth, go to our Submission to the Victorian Environmental Assessment Council’s River Red Gum Investigation, December 2006.

References:

Leslie, DJ. 2001. Effect of river management on colonially-nesting waterbirds in the Barmah-Millewa forest, southeastern Australia. Regulated Rivers: Research & Management 17:21-36.

McKinnon, LJ. 1997. Monitoring of Fish Aspects of the Flooding of Barmah Forest. Queenscliff: Marine and Freshwater Resources Institute.

Kingsford, RT. 2000. Ecological impacts of dams, water diversions and river management on floodplain wetlands in Australia. Austral Ecology 25: 109-127.

Ward, K. 1991. Investigation of the Flood Requirements of the Moira Grass Plains in Barmah Forest, Victoria. Shepparton: Department of Conservation and Natural Resources.

Briggs, SV, Thornton, SA & Lawler, WG. 1997. Relationships between hydrological control of river red gum wetlands and waterbird breeding. Emu 97: 31-42.

Healey, M, Thompson, D & Robertson, A. 1997. Amphibian communities associated with billabong habitats on the Murrumbidgee floodplain, Australia. Australian Journal of Ecology 22: 270-278.

Yorta Yorta Clans Group (1999) Final Report: Management Plan for Yorta Yorta Cultural Environmental Heritage Project.