2 Information base for the Barmah-Millewa Forest
2.1 Introduction
River red gum is a well known and widespread tree that is largely responsible for the River Murray's distinctive character and identity (Smith & Smith, 1990; Young, 2001, p. 189). The Barmah-Millewa Forest is especially important for its vast area of River red gum forest, being the largest in the River Murray system, and also the largest in Australia. The forest is located downstream of Yarrawonga Weir and comprises the floodplains of both the Murray and Edward rivers (Figure 2.1). Being Ramsar listed, the Barmah-Millewa Forest is of international significance.
The Barmah-Millewa Forest straddles the River Murray, with the Millewa Forest on the northern side of the river in New South Wales, and the Barmah Forest on the southern side of the river in Victoria. Millewa Forest is defined as the Millewa Group of Forests, which consists of a number of State Forests and National Forests, which together cover an area of 38,115 ha. The area of the Barmah Forest is 28,500 ha.
River red gum trees require frequent flooding to regenerate and grow. River red gum communities in the Barmah-Millewa Forest form dense stands 15-35 m tall, with some trees over 45 m high. The total area of the forest (66,615 ha) is approximately equal to the combined areas of the Gunbower and Koondrook-Perricoota forests and the Chowilla Floodplain.
The capacity of the River Murray at Yarrawonga is 25,000 ML/day but at the Barmah `Choke' it is only about 8,500 ML/d (equivalent to 10,600 ML/day at Yarrawonga located upstream of the Forest effluents). During floods, this constriction diverts a large percentage of the water north then west through the Edward-Wakool anabranch system. The Barmah Choke acts like a partial dam, forcing floodwater to frequently back up onto the floodplain, thereby inundating the extensive River red gum forests of Barmah-Millewa Forest-explaining the triangular shape of the forest.
Barmah-Millewa Forest is a particularly important site from an ecological perspective due to its size, the large area of River red gum forest, its carrying capacity for fauna, the diversity of species it supports, the presence of a number of rare animal and plant species, wetlands of international significance and its important role in the lifecycles of waterbirds (Maunsell et al., 1992; Stewart & Harper, 2002). There is a growing body of evidence from scientific research and other observations that maintaining the health of floodplain wetlands such as the Barmah-Millewa Forest is vital for the protection of the health of the wider river system. This is because of its important role in processes such as filtering sediments, nutrient recycling enhancing water quality, mitigating floodwaters, providing breeding and other life-cycle habitat, and replenishing nutrients and micro-fauna for birds fish and other organisms during floods (MDBMC, 1998, pp. 25-6). The health of the ecological values of the Barmah-Millewa Forest has been threatened by several factors, but a general consensus has emerged from the scientific literature that the main impact has been through river regulation, particularly through a decrease in medium-sized, spring floods, and an increase