Quiet hero of the southern Murray-Darling Basin
The lower reach of the Ovens River in Victoria is a little-known gem of the Murray-Darling Basin.
The only major floodplain in the southern Basin with a natural flooding and drying regime, the Lower Ovens effectively takes care of itself, contributing clean, filtered water to the Murray River. It’s extensive network of wetlands offers a safe nursery for a host of native fish and plant life, combined with the extensive River Red Gum forest which provides excellent habitat and food for a variety of reptiles and birdlife.
Listen to this podcast to learn more about the wonders of the lower Ovens floodplain and the groups who are working hard to manage this vital resource in North East Victoria.
The Ovens River is one of Victoria’s most iconic rivers, loved by many for its pristine waters, abundant fishing and quiet camping spots.
Ovens River – key facts
- The Ovens River is approximately 150 kilometres long from its headwaters to its confluence with the Murray River
- It flows from the heights of the Victorian snow fields, down through the Ovens River valley, past towns such as Bright and Myrtleford where it meets the Buffalo River, then on to Wangaratta where it meets the King River. The Ovens River then flows on through a lower valley, entering the Murray River at Lake Mulwala
- The upper catchment of the Ovens River is steep and dominated by native forest with some pine plantations, while the lower catchment is reasonably flat with a wide floodplain, anabranching waterways and extensive agricultural activity, including pasture, grape production and orchards
- The total Ovens River catchment area is just over 7,500 km². Rainfall varies dramatically across the catchment, with average annual rainfalls ranging from 2,000 mm at Mount Hotham to just 400 mm at Yarrawonga.
Why the Lower Ovens is special
The lower Ovens River (Ovens River below Wangaratta) and its extensive network of wetlands are in much better condition than many other rivers in the Murray-Darling Basin, largely due to the absence of major water storages and major extractions from the upper catchment.
Much of the Lower Ovens Floodplain is contained in the Warby-Ovens National Park allowing the floodplain to flood, free of most human intervention.
#1 Flooding – it’s important and valuable
Some native fish and birds rely on flooding for spawning and breeding events. The lower Ovens floodplain naturally offers these ‘flow cues’ without the need for human intervention.
That’s because the Ovens River is one of two significant rivers in the whole Murray-Darling Basin that remains unregulated. An unregulated river is one that does not have any major water storages or dams.
Larger water storages on a river have the potential to stop flooding downstream, and often reverse the seasonality of the natural flow regime.
For example, the Murray River has high summer flows to supply commercial and urban water users downstream, and low winter flows when Lake Hume and Dartmouth Dam are ‘storing’ water. This regime has reversed the natural flows of the river system, and negatively impacted on the natural ecosystem, native plants and animals, particularly some native fish and birds that rely on ‘flow cues’ for spawning and breeding events.
#2 A safe breeding ground for wildlife
High flows that come down the Ovens River, usually in in winter and spring, spill out onto the lower Ovens floodplain, filling a network of some 1,800 wetlands and bringing the area to life. This annual rhythm of natural flooding and drying creates a nursery environment for birds, fish, turtles, crustaceans, mussels, and fauna, as well as plant life.
The forests and woodlands of the lower Ovens floodplain provide important habitat for threatened fauna species such as the Barking Owl, Powerful Owl, Turquiose Parrot, Swift Parrot, Grey-crowned Babler, Painted Honeyeater, Regent Honeyeater, Apostle-bird, Squirrel Glider, and the Bush Stone-curlew. The Great Egret also has colonial nests in the swamps and wetlands.
A rich bat community relies on the dead trees on the floodplain, including the large-footed Myotis, one of only two Australian "fishing" bats that feeds by trawling its specially adapted feet along the water's surface to catch aquatic invertebrates and fish.
The Ovens River and its wetlands also provide habitat for three species of tortoise, and a diverse range of native fish, including the Murray Cod and Golden Perch and Silver Perch.
Open River Red Gum forest and an intact understorey of River Bottlebrush, Silver Wattle and Rough-barked Honey Myrtle and native grasslands provide an important continuous habitat corridor and habitat for many significant native animals.
#3 Protecting water quality in the Murray
Flooding in the Lower Ovens floodplain is important for the immediate wetlands and benefits extend into the Murray system too.
Organic matter entrained from the Lower Ovens floodplain provides a critical carbon supply for food webs and primary productivity within the Ovens River and the Murray system.
Regular flooding of the floodplain reduces the amount of leaf litter build up, which when moved off the floodplain reduces the chance of a blackwater event after a big flood.
Caring for the Lower Ovens
The lower Ovens River floodplain provides a vital link between floodplain wetland condition, hydrology, ecology, and river/floodplain/wetland connectivity.
Much is being done to care for this remarkable area and better understand its value.
A study commissioned by the North East CMA showed that 96% of wetlands are inundated on average every three years. Read more here
Through this study a number of crossings and other barriers to flow were identified through aerial mapping and flow modelling. One example was Frosts Crossing Track within the Warby-Ovens National Park which was rebuilt to provide connectivity at times of low flow within the floodplain, but still allow access into the Park.
Frosts Crossing Track prior to work
Frosts crossing after work to provide better connectivity at low flows in this section of the Lower Ovens Floodplain
Watch this You tube clip for more information:
There are still issues to manage, including: vegetation clearance, pest species, the operation of the Murray River and backwatering from Lake Mulwala, and the construction of levees, channel banks and roads that disconnect wetlands from the river.
Like to know more?
You can access further information on the Lower Ovens Floodplain within this Discussion Paper.
And the MDBA website to read more about the Ovens River.