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Lowbidgee floodplain

The lower Murrumbidgee floodplain (Lowbidgee) covers approximately 300,000 hectares and is listed in the Directory of Important Wetlands of Australia. It has supported some of the largest waterbird breeding colonies in Australia and is home to the State’s largest known population of the endangered southern bell frog and approximately 22,000 hectares of river red gum forest and woodland (part of the largest continuous forest of this type outside the Murray Valley). Lowbidgee floodplain wetlands have been affected by irrigation development, flow regulation and floodplain agricultural development over a number of decades.

RERP action

Increasing the environment’s share of available water

At the end of May 2011, RERP had purchased 26,546 megalitres (ML) of general security, 5,679 ML of supplementary access water and 665 ML of unregulated water entitlements. Combined with the Australian Government’s Environmental Water Holdings a total of 103 ML of high security, 97,888 ML of general security, 26,499 ML of supplementary access and 665 ML of unregulated water entitlement is available to the environment, in addition to environmental water available under the Murrumbidgee Water Sharing Plan.

Protecting and conserving wetlands on private land

Management agreements have been negotiated with landholders on three private properties in the area: Dundomallee, Nap Nap Station and Talpee. These agreements, covering 650 hectares, are benefiting wetlands on these properties through the fencing of wetlands to improve grazing management, revegetation activities in wetland areas and minor earthworks to improve environmental water delivery.

Yanco Creek projects

River regulation and other factors have affected the health of river red gums and caused a decline in aquatic species within parts of the Yanco Creek System. Regulating structures have been constructed at Mollys Lagoon/Dry Lake and Gum Hole/Possum Creek Complex along Yanco Creek that will allow for the reintroduction of a more appropriate drying and flooding regime and provide ecological benefits for these wetlands.

At a cost of $0.9 million, RERP has funded the installation of a fishway at Tarabar Weir (near Leeton). Yanco Creek has a range of native fish species typical of a lowland Murray-Darling stream including three threatened species (the Murray cod, trout cod and silver perch) and important populations of freshwater catfish and Murray crayfish which are in decline across much of the Murray-Darling Basin. The new Tarabar Weir fishway will allow the passage of these species to over 360km.

Yanga National Park works program

Yanga National Park covers approximately 69,000 hectares of the Lowbidgee floodplain and has some of Australia’s largest and most important waterbird breeding sites.

Flooding across the Lowbidgee Floodplain has been significantly reduced as a result of river regulation and floodplain development and consequently the area and condition of vegetation has declined. To improve water management, RERP funded a $1.6 million infrastructure program including the installation of 10 regulating structures, 10 flood-ways and the breaching of 40 pre-existing embankments. The new structures have restored the hydrologic function of the floodplain on Yanga and allow for the improved management of environmental water. Several environmental waterings have been undertaken using this new infrastructure to maintain wetland habitat and river red gum forest health, support populations of the threatened southern bell frog and maintain egret nesting sites. Management of wetlands on Yanga has been further enhanced through the installation of a gauging network (including six flow-metering stations, 17 height only sites, 11 piezometer sites and one weather station).

Fostering Aboriginal connection to wetlands

Twenty Aboriginal people participated in a RERP project to identify and record culturally significant sites across the Lowbidgee Floodplain to document the connection of Aboriginal communities to wetlands. Surveys were conducted on 13 properties and resulted in the identification of over 800 previously unrecorded Aboriginal archaeological sites, including burial sites, cooking mounds, hearths, modified (scarred) trees, mussel shell middens and areas where food, fibre and medicine plants were traditionally gathered. Follow-up conservation works have been undertaken where exposed Aboriginal burials were discovered. The oral histories of 10 Aboriginal people have also been recorded and 20 Aboriginal people have been trained in oral history recording and research skills or archaeological survey techniques to identify Aboriginal values across the wetland landscapes.

RERP has also helped facilitate a number of negotiations to allow improved access and use arrangements for Aboriginal people to culturally significant wetlands on private lands. To date, one formal access and use agreement has been signed which provides access for a local Aboriginal community to a culturally significant wetland, with negotiation on other agreements progressed.

Hydrodynamic and hydrological modelling tools

A hydrodynamic model of how water moves through Yanga National Park has been completed which will assist water managers to determine the optimum volume and timing of water releases in support of key species. This information has been used in the development of a hydrology model for the Lower Murrumbidgee floodplain, that represents the effects on the wetland of changes to infrastructure, regulation practices, dam operation rules and climate change over the short term (years) and long term (hundreds of years).

Decision Support System

Development of a Decision Support System (DSS) for the Lower Murrumbidgee wetlands has been completed, bringing together relevant areas of scientific research, to support a transparent and scientifically rigorous decision-making process. The DSS integrates the Lowbidgee ecosystem response model with the hydrologic model, allowing for the comparison of scenarios relating the volume and timing of water delivery to ecological outcomes. As it develops, this tool will assist water managers optimise the use of environmental water and sustain the identified ecological values of the wetlands.