Maintaining Flows in the Murrumbidgee River and protecting Burra Creek

The Murrumbidgee River, an important river in the Murray-Darling Basin, runs some 1,600km and its catchment covers an area of approximately 74,000 square kilometres. The Murrumbidgee Catchment supports a thriving natural ecosystem and a densely populated region of Australia. The river is home to a range of water plants, fish and aquatic life and also provides for significant economic and recreational activity.

The river supports agricultural activities including sheep and cattle grazing and crop cultivation. Its natural amenity is enjoyed by many people with recreational uses including boating, fishing and walking. Protecting the health of the river is vital in ensuring its ongoing viability for current and future generations.

About Burra Creek

Burra Creek originates in the northwest corner of the Tinderry Nature Reserve and flows in a north-westerly direction through Burra Creek Nature Reserve and intercepts with the Queanbeyan River, before discharging to Googong Reservoir. The Queanbeyan River and its tributaries are impounded by the Googong Dam to form the Googong Reservoir. The primary purpose of the reservoir is to supply potable water to the ACT and Queanbeyan.

The Googong foreshores, including the reservoir provide the venue for recreational activities including bush walking, mountain bike riding, fishing, bird watching, picnics and boating, with fishing the most popular activity. Both London Bridge limestone arch (upstream of the reservoir) and the London Bridge Homestead group are listed on the Register of the National Estate. Burra Creek is characterised by a near ephemeral flow regime and by long, narrow and shallow pools.

Both the Murrumbidgee River and Burra Creek are significant to the community as places of amenity and valued for their natural environment by local environmental and catchment groups. Both have historically been a place of cultural significance for local and regional Aboriginal people.

Environmental flows

Often referred to as environmental flows, the flow of a river plays an essential part in ensuring a healthy natural ecosystem. The level of environmental flow in the Murrumbidgee River is protected by government legislation. Within the ACT, the Environmental Flows Guidelines established by the Water Resources Act 2007, set out the volumes and timings of environmental flows and abstraction limits in streams, rivers, lakes and aquifers.

The Murrumbidgee to Googong Water Transfer will extract water from the Murrumbidgee River only in times of good flows that are above the required environmental flow level. When the flow of the river is below the level required to maintain good river health ACTEW will not extract any water. In this way the health of the river is protected.

Extracting water

Pumping water from the Murrumbidgee River is subject to the ACT’s cap on water use as agreed in the Murray-Darling Basin Agreement. This determines the total amount of water that is allowed to be diverted from the Murray Darling Basin. In times of good flows, the Murrumbidgee to Googong Water Transfer will extract up to 100 megalitres a day from the river at Angle Crossing in the ACT within the ACT Government’s water cap.

Around 50-60 per cent of any flows extracted from the Murrumbidgee River for the ACT and region’s water supply are returned to the river. The project’s net impact on average downstream flows out of the ACT is expected to be less than 1 per cent.

Environmental assessment of the Murrumbidgee River and Burra Creek

Once operational, the pipeline can transfer up to 100 megalitres a day of water from the Murrumbidgee River, through Burra Creek, to Googong Reservoir. Extensive studies of the aquatic ecology and geomorphology of the Murrumbidgee River and Burra Creek have been undertaken to make certain that it is environmentally sustainable to use the creek to transfer water to Googong Reservoir.

The impact on the Murrumbidgee River’s aquatic ecosystems is assessed as being low, especially since environmental flows will be maintained. While potential impacts identified will require management and monitoring and include erosion and bank undercutting, the studies concluded that there will be no significant environmental impacts to Burra Creek.

The specialist studies also indicate that although there may be some initial changes in the creek away from the existing conditions, this impact and any long-term changes will be within the natural variations expected in the recent past. London Bridge is a natural limestone formation located approximately 1.5km upstream of the confluence with the Queanbeyan River. The proposed pumped flows to Burra Creek will not significantly impact physically upon the geomorphology, archaeology, zoology and other values of the London Bridge natural arch.

Given the relatively low flow velocities and depths and the intermittent nature of flow predicted for Burra Creek, it is expected that impacts to macrophyte beds and movement of sediment will be low to moderate and manageable. Increased flow in the creek is likely to improve its aquatic ecology and may provide better habitat for species such as platypus.

ACTEW is developing an adaptive management program to monitor and improve the health of the Murrumbidgee River and Burra Creek. The monitoring program will be based on ACTEW’s highly successful Cotter catchment monitoring over the last 10 years. It will support other ecological management projects, such as ACTEW’s source water protection program.

The local community and other interested stakeholders will be encouraged to participate in the monitoring program and development of any adaptive response measures that may be required through establishment of an Environmental Reference Group (ERG) discussed below.

Fish Egg Filters

Alien fish species, carp (Cyprinus carpio) and oriental weatherloach (Misgurnus anguillicaudatus) are common in the Murrumbidgee River and while these species are present in the Googong catchment, they have not yet been recorded in Googong Reservoir.

Specially designed filtration screens will be used to prevent the transfer of fish eggs into the pipeline. These filters or screens will be fitted to the intake structure (low lift pump station) at the Murrumbidgee River. Four fish egg filtration units, with screen size of 0.5mm, will be installed within the intake structure at the Murrumbidgee River. The filters will be used year round, rather than only the spawning season. The screens have an automatic cleaning and flushing system to ensure proper operation at all times. The filtration screens will prevent the transfer of alien fish species from the Murrumbidgee to Googong Water Transfer to Burra Creek and the Googong Reservoir.

The Environmental Reference Group

ACTEW has established an Environmental Reference Group (ERG) to support the effective delivery of environmental management, monitoring and reporting for the construction and operation of the transfer. The ERG will enable reporting, review and consultation between community, professional, Government and ACTEW representatives for environmental, technical and community matters associated with the transfer.

The establishment of the ERG acknowledges the significant contributions of these groups to ACTEW’s water security program and provides a structure for their continued role in the successful construction and operation of the transfer.

Actions for Clean Water (ACWa) Project

In late 2009 discussions with the Upper Murrumbidgee Catchment Coordinating Committee (UMCCC) commenced regarding ACTEW’s involvement in environmental catchment issues in the Upper Murrumbidgee River. Motivated by the desire to improve the health of the river, a partnership and funding agreement was reached between ACTEW Corporation, the UMCCC, ActewAGL’s Source Water Protection Program, the Upper Murrumbidgee Waterwatch, ACT Natural Resource Management (NRM) Council and the Murrumbidgee Catchment Management Authority to establish the Actions for Clean Water (ACWa) Project.

The ACWa Project draws together partners with an interest in improving water quality in the Murrumbidgee River upstream of the confluence of the Murrumbidgee and Cotter Rivers. The project will see the employment of a project manager for 12 months to prepare a plan of action over the short, medium and long term to improve water quality. A final project report will be developed that includes recommendations on securing commitment to its implementation.