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Hattah Lakes is a complex of more than 20 semipermanent freshwater lakes over an area of 48,000 ha. The complex forms part of the Hattah-Kulkyne National Park. The complex is adjacent to the River Murray in north-west Victoria, and the ecology of the lakes and floodplain is strongly influenced by flooding regimes.

The Hattah Lakes system is naturally filled when there are high flows in the River Murray and some lakes hold water for several years after floods recede. Regulation of the River Murray has significantly reduced the frequency and magnitude of natural floods through the Hattah Lakes system. 

Large-scale engineering works were completed under the Living Murray program to improve water regimes at Hattah Lakes under low-flow conditions. Pumps and regulators are used to deliver water to parts of the floodplain and then retain and/or discharge it to provide the water regimes that support the environmental values of the system.

System map

Environmental watering objectives in the Hattah Lakes

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Provide feeding and breeding habitat for a range of waterbird species including threatened and migratory species and colonial species (such as the spoonbill and egret)
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Use flows to connect the lakes to the river so large-bodied fish (including Murray cod and perch) can move, feed and breed
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Restore a healthy and diverse mix of wetland and floodplain plant life to maintain the ecological character of this internationally protected site
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Maintain high-quality habitat for native fish in wetlands

Environmental values

Hattah Lakes provides important waterbird breeding habitat, particularly for colonial nesting waterbirds (such as cormorants). Being located in a remote and arid landscape, Hattah Lakes also provides large-scale drought refuge for waterbirds, fish and terrestrial animals. Eleven native and five non-native fish species have been reported in the lakes and five of these have conservation significance in Victoria including the freshwater catfish and fly-specked hardyhead. 

Flood-dependent vegetation at Hattah Lakes ranges from wetland communities that require frequent flooding to lignum and black box communities that require inundation two or three times a decade. The reduced frequency and duration of floods in the River Murray has degraded the water-dependent vegetation communities across the Hattah Lakes, which has in turn reduced the diversity and abundance of animals that rely on healthy vegetation for habitat.

Social, cultural and economic values

Hattah-Kulkyne National Park is a popular location for camping, canoeing, birdwatching and photography. 

The Hattah Lakes hold significance for Traditional Owners. They contain important ceremonial places and for thousands of years provided resources such as food and materials for the Latji Latji people.

Conditions mid-2017

At the beginning of 2016–17 the delivery of environmental water to Hattah Lakes was not a high priority as environmental water had been provided to Hattah Lakes three times since 2013, a dry year was expected and water allocations were low. Wetland drying was considered appropriate to allow vegetation to establish. As winter and spring progressed, conditions turned wet and it was decided to deliver water to Hattah Lakes to align with the natural conditions that were occurring throughout the region. Almost 35,000 ML of environmental water was pumped into Hattah Lakes in September and October. 

In October and November 2016, there was a major flood in the lower River Murray and the Hattah Lakes and floodplain were inundated for 16 weeks above the retention level of the lakes. Floods in major contributing systems, the Edward-Wakool and Murrumbidgee, were the largest in over two decades. Those systems washed huge amounts organic material into the River Murray, causing widespread deoxygenated blackwater and fish deaths. The water that was pumped into the lakes was not impacted by deoxygenated blackwater that arrived later during the flood, and so Hattah Lakes provided a refuge for fish and other animals from the deoxygenated blackwater present in the River Murray. 

The combination of pumping water to Hattah Lakes and two flood peaks inundated the floodplain to 44.6 m AHD. This is the second time this water level been reached since 2005, and the condition of black box trees improved in response to the flooding. However, the water did not reach trees at slightly higher elevations, up to 45.0 m AHD, which have not been inundated by floodwater since the 1970s.

Scope of environmental watering

Table 1 Potential environmental watering actions and objectives for the Hattah Lakes

Potential environmental watering1

Environmental objectives

Winter/spring fill of semipermanent wetlands

  • Maintain water in semipermanent wetlands to provide habitat for fish and waterbirds

Winter/spring fill of semipermanent and temporary wetlands

  • Improve the condition of red gum forests and woodland

Winter/spring floodplain inundation up to 45.0 m AHD

  • Improve the condition of black box woodlands

1 The Hattah Lakes pump station will also be operated to meet annual maintenance requirements.

Risk management

In preparing its seasonal watering proposal, North Central CMA considered and assessed the risks of environmental watering and identified mitigation strategies. Program partners continually reassess risks and mitigation actions throughout the water year.

Engagement

Waterway managers meet communities on environmental watering regionally, although other program partners also play a role.

In each region of Victoria, community engagement on environmental watering happens when environmental watering objectives and priorities are scoped (long term and annually), when delivering environmental water, and when reporting on environmental watering results.

In the Corangamite region communities are involved in decisions about the Moorabool river and Lower Barwon wetlands. This happens through formal advisory groups including a Moorabool stakeholder advisory and the Lower Barwon community advisory committees.

Who is engaged and how

Recreational users

The Mallee Catchment Management Authority meets with recreational users (such as fishers, bushwalkers, various 'Friends of...' groups) on an ad-hoc basis, where recreational users have an opportunity to communicate their priorities and perspectives. A gap in engagement is anglers as there is not an organised representative group.

Parks Victoria is the land manager for many of the sites that receive environmental water. Parks Victoria notifies recreational users about planned environmental water deliveries and communicates the potential impacts of environmental watering (through their website and on-site public signage).

Environment groups

The Catchment Management Authority engages environment groups (such as the Field Naturalists, Landcare and Birdlife Australia) through direct meetings 2-3 times a year. These groups provide advice, communicate their priorities and are keen to understand environmental watering objectives and outcomes. Some groups also provide information on the outcomes of environmental watering (e.g. through bird surveys.)

Landholders/farmers

The Catchment Management Authority engages the Victorian Farmers Federation, and industry groups such as table grape growers, dried fruit growers, citrus growers and landholders with river frontage or private wetlands.

These groups are engaged on environmental water planning (long term and annual scoping) and environmental water delivery. These groups are also engaged on related projects such as the Sustainable Diversion Limit adjustment proposals.

Traditional Owners

There are representatives from multiple Traditional Owner Nations from the Mallee region on the Murray Lower Darling Rivers Indigenous Nations. The Victorian Environmental Water Holder, the Commonwealth Environmental Water Office and the Murray-Darling Basin Association engage the Murray Lower Darling Rivers Indigenous Nations on strategic (often longer term) issues related to environmental watering.

Through the Catchment Management Authority Indigenous facilitator, individual Aboriginal stakeholders and groups are directly engaged throughout the year via the Catchment Management Authority Aboriginal Reference Group.

Councils

The Catchment Management Authority engages with the Mildura and Swan Hill Rural City Councils quarterly. Councils provide advice on potential community impacts of environmental watering and communicate environmental watering information back to the broader community.

General public

The Catchment Management Authority engages and communicates with the general public about environmental watering via SMS, their website, publications and media releases.