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Hattah Lakes is a complex of more than 20 semipermanent freshwater lakes over an area of 48,000 hectares. The lakes complex forms part of the Hattah–Kulkyne National Park. Located adjacent to the River Murray in north-west Victoria, 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. When floods recede some individual lakes hold water for years. The high flows that cause floods in the lakes are less than they were before, when the Murray system was unregulated.

In the absence of regular high flows in the River Murray, 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, retain and discharge water from the floodplain, to provide the water regimes that support the environmental values in the system.

System map

Murray System

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 immense waterbird breeding habitat, particularly for colonial nesting waterbirds including several species of cormorant. Being located in a remote and arid landscape, Hattah Lakes also provides large-scale drought refuge for waterbirds and other vertebrate animals. Nine 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 communities that require inundation every few years (such as lignum and black box). The lakes support more than 100 plant species that are considered rare or threatened in Victoria. One of these rare plants, the winged peppercress, is listed as nationally endangered under the Environmental Protection and Biodiversity Conservation Act 1999.

Social and economic values

Hattah Lakes is a popular location for camping, canoeing, birdwatching and photography. The lakes are also valued by Traditional Owners in the region, who have a continuing connection to the land. There are more than 1,000 registered sites of importance including burial sites, scar trees and shell middens.

Conditions mid-2016

Natural flooding at Hattah Lakes has been absent since 2011. To replicate natural floods and assist commissioning of new water delivery infrastructure, environmental water has been delivered to Hattah Lakes three times since 2013. The first two deliveries reached high elevations on the floodplain and benefited black box woodlands. Most recently, in spring 2015 water was used to top up semipermanent wetlands. The inundation extent was reduced compared to previous years, allowing a drying phase to favour vegetation on the drying beds of lakes and recruitment of river red gums.

The environmental watering over the last three years saw a range of positive results. Most notably, the condition of river red gum and black box woodlands has improved. After environmental watering, botanists recorded 80 new locations of rare or threatened plants, with a low abundance of exotic weeds. The wetlands have also benefited through nutrient exchange and release of carbon, which makes plants grow rapidly and provides optimal conditions for fish and birds to feed and reproduce.

The watering in spring 2015 provided connectivity between the lakes and the River Murray. During the watering event, golden perch that were present in the lakes were observed moving in response to environmental flows in Chalka Creek and exiting the wetlands to the River Murray. The release also provided a chance for little pied cormorants to breed and improved habitat for woodland birds including threatened regent parrots.

Scope of environmental watering

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

Potential environmental watering1

Environmental objectives

Winter/spring inundation of semipermanent wetlands (provide top-up flows as required targeting a water level of 42.5 m Australian Height Datum [AHD] July–November)

  • Maintain deeper water for waterbird breeding events
  • Maintain potential breeding habitat for fish including golden perch
  • Provide connectivity between the Hattah Lakes system and the River Murray channel

Winter/spring inundation of temporary wetlands (fill wetlands above 42.5 m AHD July–November)

  • Provide inundation of red gum forest and woodland for growth and reproduction

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

Scenario planning

In recent years the watering requirements for the red gum forest, woodlands and semipermanent wetlands at Hattah Lakes have been met, and these communities now need time to dry and allow new understorey to develop. Additional watering is not required in 2016–17 and the priority for Hattah Lakes is to provide widespread and substantial drawdowns to allow vegetation to grow and establish. As the water in wetlands evaporates it also provides lots of shallow water, which is the preferred habitat for wading birds.

Under a drought or dry scenario there are low environmental water demands in the lakes system, and water is only required to undertake annual operational maintenance of the Hattah Lakes pump station.

Natural flow cues will be used to help inform decisions to undertake larger-scale watering at Hattah Lakes if conditions are average to wet, aiming to replicate watering events that would have occurred before major dams and weirs were built.

Table 2 Potential environmental watering for the Hattah Lakes under a range of planning scenarios

Planning scenario

Drought

Dry

Average

Wet

Expected catchment conditions

  • No unregulated flows in the River Murray year-round
  • No natural inflows expected into wetlands or floodplain
Short periods of high flows in the River Murray in late winter and early spring will provide minor filling of wetlands and the floodplainLengthy periods of high flows and floods with major spills from storages, resulting in widespread inundation of the floodplain and inundating most wetlands

Potential environmental watering

  • Operational maintenance of pump station
  • Winter/spring fresh in Chalka Creek south
  • Winter/spring inundation of semipermanent wetlands
  • Winter/spring fresh in Chalka Creek south
  • Winter/spring inundation of temporary wetlands

Possible volume of environmental water required to meet objectives

  • 2,000 ML
  • 2,000 ML
  • Up to 22,000 ML
  • Up to 35,000 ML

Risk management

In preparing its seasonal watering proposal, Mallee Catchment Management Authority considered and assessed risks and identified mitigating strategies relating to the implementation of environmental watering. Risks and mitigating actions are continually reassessed by program partners 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.