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Macquarie Marshes

The Macquarie Marshes is one of the largest semi-permanent freshwater wetlands in the Murray-Darling Basin. The Macquarie Marshes provides diverse habitat varying from almost permanently wet areas to floodplain areas which may only flood once in ten years. As a consequence it is a biodiversity hot spot. It hosts rare, endangered and vulnerable species and is one of the most important sites in Australia for colonial waterbird breeding. Around 19,000 hectares are listed under the Ramsar Convention as Wetlands of International Importance.

RERP Action

Increasing the environment’s share of available water

At the end of January 2011, RERP had purchased 42,263 megalitres (ML) of general security and 140 ML of supplementary water access entitlements. Combined with purchases under other State and Australian government programs, the environment’s share of available water has increased by over 60 per cent compared with the existing 160,000 ML Environmental Contingency Allowance provided by the Water Sharing Plan for the Macquarie-Cudgegong Regulated River Source 2004.

Community engagement activities

RERP has funded a number of community events to bring landholders, community members and NSW agency staff together to share knowledge and experiences of the Macquarie Marshes. Events have included the ‘Macquarie@Macquarie’ Workshop at Quambone in August 2009 and a holistic grazing workshop held in February 2010, where soils, grazing regimes and cost-effective measures to meet different challenges in wetland grazing systems where discussed.

Pillicawarrina State Conservation area

In January 2009, RERP contributed to the purchase of 2,436 hectares of the property Pillicawarrina. The property has been added to the adjoining Macquarie Marshes Nature Reserve and is managed by OEH’s Parks and Wildlife Group.

The purchase of the property is significant as it allows restoration of the principal floodplain that connects to the Ramsar-listed Nature Reserve. Since the purchase, RERP has invested over $600,000 in rehabilitation works on the floodplain, including removing redundant levees and other structures to reinstate the flow of floodwater across the floodplain and modifying other in-stream structures to be more fish friendly.

A revegetation strategy has also been developed that will guide efforts to rehabilitate areas previously cleared and used for cropping.

Fish passage restoration

RERP funded the construction of a new fishway at Marebone Weir, 50 kilometres north of Warren. Costing $3.2 million, the fishway will improve the connectivity of fish communities in the Macquarie River and the Macquarie Marshes by allowing free movement of fish along an additional 214 km of river. The fishway includes a carp trap.

Bulgeraga Creek is a major waterway of the Macquarie Marshes downstream of Marebone Weir, with numerous in-stream structures impeding fish passage. As part of RERP, State Water owned structures along Bulgeraga Creek were assessed by a fish biologist to ascertain their impact on fish passage with two priority structures replaced with culverts.

Burrendong Dam cold water pollution remediation

RERP and State Water have funded an assessment of a floating ‘curtain’ device as a possible solution to cold water pollution from Burrendong Dam. The study demonstrated the feasibility of a constructed curtain that shrouds the lower levels of the outlet tower, forcing the release of warm water from shallower depths. The modelling has predicted a significant improvement in release temperatures under a range of climate and management scenarios. The investigation also considered a range of management issues, including reducing the potential for algal blooms.

This innovative and cost-effective solution to a key environmental issue could provide substantial benefits for the ecology downstream of the dam when constructed. The design could also be used at other dams of a similar configuration.

North Marsh bypass channel

The North Marsh bypass channel is used by State Water to supply stock and domestic water to landholders downstream of the Macquarie Marshes. RERP funded an investigation of options for the provision of a more reliable stock and domestic water supply while also delivering water savings and environmental benefits. The investigation compares options for future works and provides a hydrological and ecological baseline upon which the outcomes of future works can be assessed.

Buckiinguy Swamp geomorphic study

Buckiinguy Swamp is a privately owned 500-hectare wetland in the southern Macquarie Marshes. Silt appears to be obstructing the flow of water into the northern parts of the wetland and diverting water away from the southern Macquarie Marshes. RERP funded a study to define the current state of the wetland, recording erosion and deposition of sediments over time and developing future management options.

Wilgara erosion control trial

The privately owned property Wilgara has 550 hectares of wetland in the eastern part of the marshes including a section of the Macquarie Marshes Ramsar site. Stock exclusion and the use of wetland plants was trialled to stabilise the bed and banks of eroding channels.

The results of the trial has application to shallow channels throughout the marshes and other similar inland systems where wetland plants are absent and bed and bank erosion is present.

 

Grazing management on privately owned wetlands

Four landholders in the Macquarie Marshes were successful in gaining incentives to assist in grazing management projects. Over 1,480 hectares of river channels, wetlands and floodplains on private land are covered by these incentives. Projects include fencing, alternative watering points and treatments to improve biodiversity of native groundcover on the properties The Mole, Quilbone, South Roubaix and Cutbushes.

Research to better understand complex wetland ecosystems

A number of research projects have been undertaken to compile:

• vegetation community condition and extent mapping providing fundamental data for delineating wetland assets and for input into ecosystem responses models;
• the recent history of inundation for over 20 flood events in the Macquarie Marshes; and
• relationships between the response of key species and the delivery of environmental flows.

New river gauges at Oxley Break and Pillicawarrina will improve knowledge about the delivery of environmental flows and how they are distributed.

Hydrodynamic modelling

 

A hydrodynamic model has been developed to analyse and predict how water moves through the Macquarie Marshes. The model will assist water managers in targeting areas for environmental flows in support of wetland health.

 

Hydrological modelling

Using information from the hydrodynamic model, a hydrological modelling tool has been developed to better link the Macquarie Marshes to the catchment hydrology model used to manage water in the Macquarie valley.

Decision Support System

Development of a Decision Support System (DSS) for water management in the Macquarie Marshes has been completed and brings together relevant areas of scientific research. The DSS is the culmination of investment in science undertaken through RERP and integrates ecosystem response models with hydrologic models, allowing for the comparison of scenarios relating the volume and timing of water delivery to ecological outcomes.