Emerald Messenger

As stage 4 restrictions are easing across Melbourne you may be thinking about some places to visit when it is safe to do so. The Christmas holiday’s normally see countless Melbournian’s packing their cars and heading to the northern states. If restrictions permit, I suggest heading out and exploring somewhere a little closer to home – there is an abundance of special places in Victoria.

Rivers are some of the most dynamic and human-altered environments on earth. We rely on them for food, water, energy and recreation. Ever increasing demands for our most precious resource, water, coupled with climate change is having a serious and detrimental impact on riverine ecosystems. The protection and restoration of rivers can have both social and environmental benefits. The catchment landscape large scale Budj Bim restoration project in south western Victoria is one such project.

The Budj Bim Cultural Landscape was inscribed on the World Heritage List in 2019, within the traditional Country of the Gunditjmara Aboriginal people. Approximately 20-30 thousand years ago the eruption of Budj Bim (formerly known as Mount Eccles) and Mount Napier irreversibly altered the landscape and drainage patterns as lava flowed in a westerly direction forming the Budj Bim volcanic plains. Budj Bim is an extensive wetland environment of sinkholes, swamps, lakes, limestone caves and rocky outcrops intersected by the Killara Creek, the Fitzroy River and the Fitzroy River Estuary. Within this newly formed landscape there is evidence of one of the oldest aquaculture systems in the world. Established approximately 6600 years ago by the ancestors of the Gunditjmara people, along the basalt lava flows known as the Tyrendarra flow, there is a complex system of ponds and traps formed out of stacked rocks. These rock formations were engineered to trap eels (Anguilla australis) and other fauna, forming a permanent to semi-permanent food source for the Gunditjmara people.

Since European settlement there has been a number of threatening processes that have led to the landscape becoming degraded, including;  the clearing of native vegetation (predominantly for sheep grazing), the artificial draining of wetlands as well as the constructions of dams and weirs. This altered ecosystem, enabled the rapid spread of invasive weeds and pollutants. Land clearing, riparian destruction and an altered flow regime further exacerbated the hydrological and ecological disconnect between the rivers and their floodplains. This hydrological disconnect further impacted the life histories of many species, including the catadromous migrating eel (kooyang) as they journeyed longitudinally towards the sea from their inland freshwater habitat.

The historic draining of Tae Rak (Lake Condah) and the construction of levees for flood protection rendered the ancient aquaculture system inactive without adequate flows to support both flora and fauna. The World Heritage Listed Budj Bim region, to which this restoration project is bounded, contains 3 Indigenous Protected Areas (IPA), private farmland and a national park. Part of the motivation for this project of enriching cultural connections is also to create an opportunity for cultural redress for damages to the traditional way of life of the ancestors of the Gunditjmara people and their ancient practice of aquaculture. The historical knowledge of 6600 years was integral to both the setting of ecological targets as well as having a reference point or goal for the project.

The overall aim of this large-scale restoration project was to:

reconnect the rivers and creeks to their floodplains and wetlands both hydrologically and ecologically, through a number of smaller restoration projects across the Budj Bim Cultural Landscape.

Improve the condition of both the aquatic and native vegetation habitat that would enable the support of the kooyang as well as threatened species such as the Yarra pygmy perch, Glenelg spiny crayfish, Australasian bittern and the growling grass frog.

Enrich cultural connections to country by integrating both indigenous knowledge of managing country with western science.

The on-ground works, in the northern part of the project, that were undertaken after a hydrological feasibility study included installing a new weir, installing a surface-water modelling gauge, installing a by-pass channel structure and removing fish barriers. In the middle and southern part of the project (within farmland) there was 8.4km of waterway fencing done to increase the riparian zone (area adjacent to a riverbank), 76 ha of weed control, off-stream stock watering and the removal of well over 1000 willow trees.

The riverine environment is constantly adapting and changing in response to the variability in hydrological and sediment inputs. Upgrading the weir and installing a channel bypass at Tae Rak is helping to control the water levels and reconnect the creek to its floodplains and wetlands.

Floodplains and wetlands are an integral part of the lifecycles of most riverine fish species, where many species move across to the wetlands during high flow events for feeding, spawning, nursery and protection. Monitoring changes in the hydrological connectivity between the creek and its floodplains is vital to understanding the habitat requirements and any changes in biodiversity. The surface-water modelling gauge enables the water levels to be monitored and precisely controlled remotely in response to increased (flood) or decreased flow events to enhance the ecological value of the river system.

Willows are an introduced invasive species that were initially and historically planted along riverbanks to help stabilise them. Unfortunately, in the riverine environment willows out-compete native vegetation forming high density thickets that disrupt channel hydraulics and reduce aeration. During autumn, willow trees which are deciduous drop their leaves causing an influx of organic matter into the waterways. Native macroinvertebrates which have evolved to breakdown native leaves that fall all year-round and slowly break down, are not able to breakdown willow leaves. Macroinvertebrates act as a food source for most riverine fish species. A reduction in macroinvertebrates causes a reduction in native fish species. Willow trees can further cause a reduction in biodiversity by shading the waterways, reducing the water temperature and thus further inhibiting primary production. Stock exclusion from rivers and increasing the riparian zone will reduce point-source pollution and erosion which in turn will improve water quality.

The Budj Bim restoration project is a collaboration between the Gunditj Mirring Traditional Owners Aboriginal Corporation, the Budj Bim Rangers and the Glenelg Hopkins Catchment Management Authority. The long-term investment from the Victorian Government of $1.5 million over 24 years ensures that this project has the longevity to restore flow regimes, increase riverbank vegetation, enhance biodiversity as well as connecting aboriginal people to waterways, country and their cultural practices.

The anguilla australis (short finned eel) are an amazing catadromous species that spawn in the Coral Sea below Papua New Guinea; they then travel on currents down the east coast of Australia and New Zealand and journey up the rivers in search of freshwater lakes and wetlands where they spend most of their life until maturity (up to 30 years). When it’s time to spawn, they make the return trip all the way back to the Coral Sea. I grew up going ‘eeling’ with my Dad, dragging around his handmade ‘Hinaki’ (eel trap) to the local dams where Dad would drop the Hinaki into the dam in the morning and then we would check it in the evening. Dad would then smoke the eels in his home-engineered smoker for days where the (horrid) smell of smoking eel would be wafting around the neighbourhood.

www.citycollection.melbourne.vic.gov.au/short-finned-eel-anguilla-australis/

www.createdigital.org.au/an-enduring-indigenous-engineering-project-illuminates-a-path-to-a-sustainable-future/

Heremaia Titoko

Final year Environmental Science student, Charles Sturt University

Categories: November 2020