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The ecology of the Hattah Lakes and surrounding floodplain is strongly influenced by flooding regimes of the River Murray. The system fills when there are high flows in the River Murray, and some lakes hold water for numerous years after floods recede. Regulation of the River Murray has significantly reduced the frequency and duration of small- to medium-sized natural floods in the Hattah Lakes system. Over time, this has degraded vegetation communities and reduced the diversity and abundance of animals that use the vegetation and wetlands for habitat and food.

The Hattah Lakes complex can be broadly divided into the southern Hattah Lakes, which contain permanent to semi- permanent wetlands, and the higher-elevation northern Hattah Lakes, which are mostly ephemeral wetlands.

The Messenger, Oateys and Cantala regulators allow water to flow between the River Murray and the Hattah Lakes. When flows in the River Murray are about 26,000 ML per day, water begins to flow through the Messenger regulator into Chalka Creek and through to the Hattah Lakes complex. A permanent pump station has also been constructed that can deliver up to 1,000 ML per day to Hattah Lakes through Chalka Creek. The regulators and pump station are used in combination with several small constructed levees to restore a beneficial pattern of flooding to the lakes.

Lake Kramen in the south-east of Hattah-Kulkyne National Park is disconnected from the main Hattah Lakes complex. The Hattah Lakes pump station can deliver up to 145 ML per day to Lake Kramen to restore flooding regimes.

Traditional Owners

System map

Environmental watering objectives in the Hattah Lakes

icon-objectives-fish
Increase the native fish populations
Plant icon
Restore and maintain a mosaic of healthy wetland and floodplain plant communities
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Provide feeding and nesting habitat for the successful recruitment of waterbirds and woodland birds

Environmental values

Hattah Lakes is home to a diverse range of flood-dependent vegetation that changes with the topography of the landscape. Vegetation types range from wetland communities in lower-lying areas that require almost annual flooding to lignum and black box communities situated higher on the floodplain that only need flooding once every four to five years (on average).

A combination of natural flooding and the delivery of environmental flows since 2010 has improved tree canopy health and recruitment of black box and river red gum communities throughout the Hattah Lakes. Woodland birds, including the endangered regent parrot, have benefited from the improved tree health.

Hattah Lakes provides important waterbird breeding sites in an arid landscape. A total of 34 species of waterbirds are known to breed at the lakes when conditions are suitable. Another six species of waterbirds breed in the surrounding floodplain. Wetland drought-refuge sites are limited in the region, making Hattah Lakes critically important for waterbirds and terrestrial animals.

The Hattah Lakes support native fish species such golden perch and endangered freshwater catfish, which can move between the lakes and the Murray River when flows are suitable. Fish can also persist in permanent wetlands in the Hattah Lakes during dry years.

Traditional Owner cultural values and uses

The Hattah Lakes system is part of a highly sensitive region for Aboriginal cultural heritage values and contains considerable evidence of past Aboriginal occupation. More than 1,000 Indigenous archaeological sites at the Hattah Lakes are registered with Aboriginal Victoria. The local Aboriginal community maintains strong connections to the land and its resources such as native species used for food and medicine.

Mallee CMA and members of Tati Tati, Latje Latje, Gilby Corporation and Munutunga discussed a range of options for how environmental flows can be delivered at Hattah Lakes in 2020–2021. Elders spoke of the importance of drying cycles for wetlands and the abundance of the culturally significant old man weed that is flourishing on the drying lake beds. They also warned of not leaving the system dry too long and provided advice on the method of mimicking natural inundation when water does return. Their recommendations for watering actions have shaped environmental water planning for 2020–21.

Social, recreational and economic values and uses

In planning the potential watering actions in Table 1, Mallee CMA considered how environmental flows could support values and uses including:

  • water-based recreation (such as canoeing, kayaking and fishing)
  • riverside recreation and amenity (such as camping, photography, birdwatching and bushwalking) community events and tourism (such as 'Junior Ranger' school holiday programs including bushwalking, birdwatching and bug hunting, school education programs, citizen science projects (microbats), tours involving kayaking, mountain bike riding, camping, fishing and swimming)
  • socio-economic benefits (such as beekeeping).

Recent conditions

Weather observations at the nearest weather station to Hattah Lakes in Ouyen indicate there was below-average rainfall and above-average temperatures in the area during 2019–20. The average maximum temperature at Ouyen during 2019–20 was less than the previous year, but long-term data indicates that temperatures have increased over the previous 10 years. Rainfall totals were substantially below average for the year. Overbank flows from the Murray River affect the ecology of the Hattah Lakes floodplain more than local weather conditions, but the trend of increasing temperature and decreasing rainfall is harmful to plant and animal communities between floods.

2019–20 was dry across the entire Murray River valley and the major upstream tributaries that contribute flows to the mid-Murray river system. There were no spills from major upstream storages and the magnitude of operational flows and environmental flows that were released was well below the threshold for inflows to Hattah Lakes. Decisions about environmental watering interventions at Hattah Lakes during 2019–20 focussed on the need to water Lake Kramen — a disconnected wetland at the fringes of the system — and the need to dry the main southern Hattah Lakes.

At Lake Kramen, observations of tree health indicated that environmental watering was necessary during spring 2019 to avoid a permanent decline of vegetation condition, therefore environmental water was released as planned to Lake Kramen during August to October 2019.

Water for the environment delivered the last flood in the southern Hattah Lakes wetland complex in 2017. The wetlands have been allowed to draw down since then, and the last wetlands to hold water dried in February 2020. The moisture remaining in the lake-bed soils and local rainfall is supporting the growth and recruitment of specialised lake-bed native vegetation.

If there is no natural wetting before autumn 2021, the lake-bed vegetation in the southern Hattah Lakes will have likely completed its life cycle and will die off, due to reduced soil moisture. Water for the environment may be used in autumn/winter 2021 to refill these wetlands and restart the important wetting and drying cycle. Lake Kramen is expected to gradually draw down over several years. The planned timing of future environmental watering at Lake Kramen will be determined by the condition of the fringing vegetation.

Scope of environmental watering

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

Potential environmental watering action1

Functional watering objective

Environmental objectives

Southern Hattah Lakes (fill of selected wetlands during autumn/winter 2021)

  • Stimulate the growth and improve the condition of river red gums
  • Provide refuge and feeding habitat for waterbirds
  • Stimulate the growth of aquatic vegetation in wetlands that are currently dry
Plant iconHeron icon

Hattah Lakes (floodplain inundation up to 45.0 m AHD at any time if there is a natural flood)

  • Wet river red gums and black box on the floodplain to stimulate growth and improve the condition of mature trees
  • Provide suitable soil conditions for the germination of black box trees on the floodplain and support the growth of trees that germinated in the flows provided in 2017
  • Provide suitable conditions to support waterbird and woodland bird breeding and feeding
  • Provide connections to allow native fish to move between Hattah Lakes and the Murray River
  • Provide spawning and recruitment habitat for small-bodied native fish and nursery habitat for large-bodied native fish (such as golden perch)
Fish iconPlant iconHeron icon

1The Hattah Lakes pump station may also be operated at any time of year for annual maintenance requirements.

Engagement

Table 2 shows the partners and stakeholder organisations who have assisted the Mallee CMA prepare the Hattah Lakes seasonal watering proposal.

Seasonal watering proposals are informed by longer-term regional catchment strategies, regional waterway strategies, environmental flow studies, water management plans and other studies. These incorporate a range of environmental, cultural, social and economic perspectives and longerterm integrated catchment and waterway management objectives. For further details, refer to the Mallee Regional Catchment Strategy and the Mallee Waterway Strategy.

Table 2 Partners and stakeholders engaged in developing the Hattah Lakes seasonal watering proposal

Partner and stakeholder engagement
  • Local Landcare groups
  • Mid-Murray Field Naturalists
  • Commonwealth Environmental Water Office
  • Murray-Darling Basin Authority (the Living Murray program)
  • Parks Victoria
  • Goulburn-Murray Water
  • Department of Environment Land, Water and Planning (Fire Forest and Regions)
  • Department of Environment Land, Water and Planning (Water and Catchments)
  • Mildura Rural City Council
  • Landholders and farmers who live around the Hattah Lakes
  • Hattah Store owners
  • Mallee Tours
  • Murray Offroad Adventures
  • Mildura Information Centre
  • Visit Mildura
  • Wild Side Outdoors
  • Sunrasia Apiarist Association
  • Birdlife Mildura
  • Sunraysia Bushwalkers
  • Four-wheel drive club
  • Mallee CMA Land and Water Advisory Committee
  • CollaborateTraditional Owners of Hattah Lake (Aboriginal Victorians from Wadi Wadi, Tati Tati, Latje Latje and Munutunga)

Page last updated: 24/07/20