Linking river red gum condition to hydrological change at Yanga National Park
Yanga National Park is located on the Lowbidgee f loodplain of the Murrumbidgee catchment (Fig. 15.1/colour plate, p. 314). It is classified as warm, persistently dry grassland under the modified Köpen classification system (Stern et al. 2000). It has a semi-arid climate with low annual rainfall and hot summers. Mean summer maximum temperatures range between 30.9°C and 33.0°C, and mean winter minimum varies from 3.5°C to 6.8°C. Multi-year mean annual rainfall is 320 mm with considerable interannual variation (BOM 2008). Yanga National Park is renowned for its large stands of river red gum (Eucalyptus camaldulensis) forests and woodlands that are critical fish and waterbird habitats and refuge for biodiversity in arid and semi-arid Australia (Maher 1990; Kingsford and Thomas 2001; Watts et al. 2003; Gilligan 2005). In the natural state, many of the river red gum forests in the region are characterised by variable and unpredictable patterns of high and low flows and water levels. Over the past 50–100 years, the wetlands on the Lowbidgee f loodplain have changed significantly from their natural state (Kingsford and Thomas 2001). The ecosystem is experiencing degradation due to in-stream regulation structures (e.g. dams and weirs), f lood prevention structures (e.g. levees), deterioration of water quality, clearing of riparian vegetation and grazing, and the presence of exotic species (Hillman et al. 2000). Of these factors, altered f low regime is believed to be an important contributor (Kingsford and Thomas 2001; Wen et al. 2009). Major restoration effort is therefore directed to environmental water allocation aiming to re-establish the ecological integrity of the river-f loodplain ecosystem.