Rivers and Streams

Rivers and streams are iconic in the Wimmera, given it is a largely semi-arid region and many social, economic, cultural and environmental values are provided by the region’s waterways. The catchment’s rivers and streams are distinguished by a temperate to semi arid climate. Severe droughts and large floods make for variable hydrology and the adaption of unique and important riparian and aquatic ecosystems.

The Wimmera’s two river basins are the Wimmera-Avon Basin comprising most of the region’s east and the Millicent Coast Basin covering the western part of the region. The Wimmera basin comprises part of the Murray Darling Basin and extends north and east into the Mallee and North Central Catchment Management Authority (CMA) regions.

The major waterway in the Wimmera-Avon Basin is the Barringgi Gadyin (Wimmera River) which is the largest river in Victoria that cannot flow out to the sea.

Figure 5 Major rivers and streams in the Wimmera

Major rivers and streams in the Wimmera

It’s catchment has numerous tributaries arising in Mount Buangor State Park, the Pyrenees range, Gariwerd (Grampians National Park) and the Black Range Scenic Reserve near Stawell. The Barringgi Gadyin (Wimmera River) flows through Glenorchy, Horsham, Quantong, Dimboola and Jeparit before entering Gurru (Lake Hindmarsh).

During exceptionally wet periods, Gurru (Lake Hindmarsh) will fill and spill into Outlet Creek and onto Ngalpakatia/ Ngelpagutya (Lake Albacutya), an internationally significant Ramsar–listed wetland. The catchment extends beyond Ngalpakatia/Ngelpagutya (Lake Albacutya) into the Mallee CMA region with numerous smaller lakes before reaching the Wirrengren Plain. Historic records show occasional flooding of lakes beyond Ngalpakatia/Ngelpagutya (Lake Albacutya), though they have not received floodwater since the 1970s.

The Barringgi Gadyin (Wimmera River) between Polkemmet and the Wirrengren Plain has been proclaimed a Victorian Heritage River due to its significant environmental, cultural and social values (Heritage Rivers Act 1992).

A notable feature of the system is the distributaries, Dunmunkle and Yarriambiack Creeks, which carry water from the Barringgi Gadyin (Wimmera River) during high flows and floods. Yarriambiack Creek flows from Longerenong through Jung, Warracknabeal and Brim and onto Lake Coorong near Hopetoun in the Mallee. The Dunmunkle Creek is a highly modified stream that carries water north from Glenorchy through Rupanyup, dissipating in the southern Mallee.

The Wimmera Basin also contains a few stand-alone streams that flow into wetlands, for example Natimuk Creek feeds Natimuk Lake and Lake Wyn Wyn. The Millicent Coast Basin extends south into the Glenelg Hopkins CMA region and west into south-eastern South Australia. It is characterised by several streams that flow west. Mosquito Creek is an important stream as it flows from south- west of Edenhope through to the Bool and Hacks Lagoons Ramsar site near Naracoorte.

The Wimmera’s rivers and streams provide most of the water needed for towns and farms, especially via the Wimmera Mallee Pipeline. Many townships are located adjacent to rivers and streams for historic water supply, recreational and aesthetic purposes, so many have weirs to retain water levels through drier periods. Rivers and streams underpin local tourism and recreation. Camping, fishing, walking, canoeing, rowing, bird watching and swimming are popular activities that local residents enjoy. These attractions bring visitors to the region and significant tourism dollars.

The Wimmera’s rivers and streams also support significant local events such as fishing competitions, rowing regattas and festivals. A study into the socio-economic value of environmental water demonstrated that the Barringgi Gadyin (Wimmera River) alone generates around $4.75 million a year and has additional health benefits for the community worth $2.5 million annually.(6)

Rivers and streams support some irrigation of grape vines, pasture and annual crops. Water is also supplied to local industry, intensive agriculture and mining enterprises.

Rivers and streams form natural corridors in a largely agricultural landscape and a large variety of wildlife rely on them for habitat. Examples include freshwater catfish (Tandanus tandanus), river blackfish (Gadopsis marmoratus), western swamp crayfish (Gramastacus insolitus), rakali or water-rat (Hydromys chrysogaster) and platypus (Ornithorhynchus anatinus).

The corridors of native vegetation that parallel rivers (riparian corridors) provide vital habitat for a variety of bird life, vegetation and other species. For example, bird surveys have highlighted the importance of habitat adjacent to waterways with higher abundance and diversity of birds recorded. The north to south running corridors provided by the Wimmera River, Yarriambiack and Dunmunkle Creeks and some southern streams could play an important future role in facilitating the migration of species like nationally threatened regent parrots (Polytelis anthopeplus) and Major Mitchell’s Cockatoo (Lophochroa leadbeateri) to suitable southern habitats under hotter and drier climate change scenarios.

There is occasional flooding of towns across the Wimmera. Floods can severely disrupt communities by causing property damage, personal hardship, regional economic loss, injury and potentially loss of life.