ABOUT THE FOCUS CATCHMENTThe Ovens and Goulburn rivers contribute signifi cantly to the water resources of the Murray-Darling Basin. These two rivers are similar in many ways in terms of their geomorphology, land-use, and vegetation communities, but their hydrology is vastly different. The Ovens River is largely unregulated while the Goulburn is highly regulated.

With a population of over 200,000 spread over 25,000 km2, these two catchments occupy much of the area known as the food bowl of the Murray-Darling Basin. Irrigated and dryland agriculture are very important, and the region contributes signifi cantly to the Victorian and national economies.

Both rivers also have high environmental values and natural biodiversity. For example, the region includes the Barmah Forest — an internationally recognised wetland system and part of the largest river red gum forest in the world.

In their natural state, both rivers’ off-channel fl oodplain wetlands, redgum forests, and other ecosystems would be strongly infl uenced by seasonal fl ooding. Although the Ovens River still fl oods frequently, the Goulburn River, regulated by Eildon Dam, does not. Reduction in seasonal fl ooding affects the long-term condition of the rivers’ important riparian ecosystems.

APPLICATIONThis eWater application is helping identify how potential fl ow scenarios could affect the river and fl oodplain ecology of the area.

Besides its strong research component, eWater’s work in this focus catchment involves applying a range of the CRC’s next-generation software tools, in:

(i) hydraulic and fl ow modelling of streamfl ow in the Goulburn River and its tributaries, in relation to its fl oodplain;

(ii) building up information about ecological responses in these catchments; for example, how fl oodplain vegetation responds to changes in fl ow conditions through time;

(iii) developing and evaluating models of ecological response.

eWater CRC is working on local water-management issues in partnership projects with organisations in northern Victoria.

Focusing on the Goulburn and Ovens river catchments, the project teams are exploring the ecological value and benefi ts (or disbenefi ts) if off-channel habitats were to be deliberately rewetted.

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REWETTING OF DRY FLOODPLAINSFlooding of dry fl oodplains can be benefi cial or pose risks for the fl oodplain ecosystems. River red gums and other fl oodplain and wetland vegetation, as well as waterbirds, resident fi sh and water bugs, may be rejuvenated by the watering. In refuge pools, rewetting can be the difference between surviving or succumbing to the pressures of water quality and quantity, predation and habitat loss that often accompany drought.

But the duration of wetting is very important. Unless the water stays for a suitable length of time the natural cycles it triggers may not be completed. And the timing of watering matters as well: for instance, delivering water during very hot summer weather carries a risk of ‘blackwater’ events that can lead to fi sh deaths.

eWATER’S INPUTIn the Goulburn and Ovens rivers, eWater’s research is helping identify the ecological assets, including key ecological communities, indicators of condition, and important habitats. The team is also identifying groundwater-dependent wetlands and refuges.

The application is integrating ecological and hydrological modelling expertise to review existing information on the role of overbank fl ows in maintaining riparian ecosystems. The team can then evaluate the likely ecological effects of restoring such fl ows in the Goulburn river system.

By combining rainfall-runoff, fl ow routing and hydraulic models, the project team is also exploring scenarios of potential climatic conditions (based on historical and predicted events) in relation to rewetting off-channel habitats. This will give insight into the infl uence of tributary infl ows on fl ood heights. The team is also investigating options for piggybacking of fl ow releases onto natural fl ow events.

OUTCOMESThis research and accompanying trial of eWater software in northern Victoria is exploring and summarising how key ecological indicators are likely to respond to alternative future-fl ow scenarios, including fl oodplain wetting events, along the lower Goulburn and Ovens rivers.

It will also result in a management database identifying high priority areas for refuge management along the Goulburn River, based on the dynamics of groundwater-surfacewater interactions.

The models will be developed in such a way that the general approach and information requirements may be applied to similar river situations elsewhere.

ORGANISATIONS INVOLVED

These eWater partner organisations are involved in this project:

Environment Protection Authority (Victoria), Department of Primary Industries (Victoria), Goulburn-Broken Catchment Management Authority , North East Catchment Management Authority, Goulburn-Murray Water, and The University of Melbourne.

KEY CONTACT

Northern Victoria Focus Catchment Coordinator:Wayne Tennant, Goulburn-Broken CMAwaynet@gbcma.vic.gov.au

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All eWater tools demonstrated in focus catchments are part of our integrated modelling suite.

August 2009