Conditions 2018
Higher-than-average rainfall at the start of the 2017–18 water year saw the Murray system seasonal determination rise from an opening 66 percent to 100 percent highreliability water shares by October 2017. Despite high rainfall in November and December 2017, natural inflows to the central Murray wetlands were limited by artificial barriers (such as channels, roads and levees). Water for the environment was therefore the primary source of water for most wetlands in the region. Water for the environment was delivered to seven of the central Murray wetlands in 2017–18.
In Round Lake and Lake Elizabeth, water for the environment was used to periodically top-up water levels to maintain suitable water-quality conditions for endangered Murray hardyhead. Round Lake maintains a stable population of Murray hardyhead. Recent monitoring undertaken as part of the statewide Wetland Monitoring and Assessment Program (WetMAP) for environmental watering detected more than 20 Murray hardyhead at Lake Elizabeth, which indicates that the translocation of Murray hardyhead in 2016 was successful; and there is evidence of subsequent recruitment. This is an extremely positive result for the site, as it only started receiving water for the environment in 2014.
Water for the environment was used to support waterbirds, plants and other animals typical of temporary freshwater marshes at Richardsons Lagoon, Wirra-Lo wetland complex, Hird Swamp, McDonalds Swamp and Lake Murphy.
The filling of Richardsons Lagoon marked the completion of the three-year watering cycle recommended in the Richardsons Lagoon Environmental Water Management Plan. Waterbird monitoring has demonstrated that the lagoon and its surrounding woodland support up to 52 bird species including 28 waterbird species. The number of bird species recorded at Richardsons Lagoon in 2017–18 was slightly higher than in recent wet years. Observations of juvenile black swans and nankeen night herons suggests there has been successful bird breeding at the wetland. Richardsons Lagoon will be allowed to draw down and dry over about three years, before it is due to receive more environmental water.
Delivery of water for the environment to Wirra-Lo wetland complex at Duck Creek North and Duck Creek South in spring/summer 2017 aimed to provide refuge habitat and suitable breeding conditions for the nationally-endangered growling grass frog as well as create high-quality feeding and breeding habitat for waterbirds. Growling grass frogs were heard calling at Wirra-Lo wetland complex in summer 2017–18, and this is the first record of growling grass frogs on the Murrabit West floodplain since 2008. The return of the growling grass frog to Wirra-Lo wetland complex within four years of rehabilitation works demonstrates the benefits of providing water for the environment.
Water for the environment supported large numbers of waterbirds at Hird Swamp in 2017–18. Regular monitoring consistently recorded about 40 waterbird species at Hird Swamp between October and December 2017. The greatest abundance of waterbirds recorded in a single survey at Hird Swamp was 2,743 individuals in November including 600 Australasian grebes. Many threatened species were recorded at Hird Swamp in 2017–18 including Baillon's crake, whiskered tern, glossy ibis, royal spoonbill, eastern great egret, Australasian bittern, Australasian little bittern, magpie goose, white-bellied sea eagle, musk duck and nankeen night heron. There was also evidence of bird breeding at Hird Swamp in spring and summer 2017–18 as juvenile waterbirds from various species including black swan, banded rail and brown quail were recorded. A brolga nest with two eggs was discovered in early February 2018, but these were later reported missing, likely due to predation.
No water for the environment was delivered to Johnson Swamp, Lake Cullen or Guttrum and Benwell forests in 2017–18. Johnson Swamp and Lake Cullen were managed for drying and drawing down respectively. Some parts of the Guttrum and Benwell forests received natural inflows during early summer 2017 from high flows in the River Murray. However, most of the forest understorey and wetlands remain in poor condition. The forests require a more-natural watering regime to support recovery from the Millennium Drought and historical grazing pressure.
Scope of environmental watering
Table 1 shows potential environmental watering actions (including wetland drying) and their environmental objectives.
Table 1 Potential
environmental watering actions and objectives for central Murray wetlands
Potential
environmental watering | Environmental objectives |
|---|
Wetland watering |
Guttrum and Benwell forests (fill Reed Bed Swamp and Little Reed Bed Swamp in winter/ spring and autumn/winter, top-ups to support bird breeding)1 | - Rehabilitate aquatic vegetation, semiaquatic vegetation and river red gum communities in semipermanent wetlands
- Provide feeding, breeding and refuge habitat for waterbirds, frogs and turtles
- Support colonial waterbird breeding, if it occurs
|
Johnson Swamp (fill in spring) | - Provide feeding and breeding habitats for waterbirds
- Minimise the growth of tall marsh vegetation
|
Lake Cullen (spring fill) | - Support waterbird populations by providing suitable roosting and feeding habitat
- Increase the growth and recruitment of aquatic vegetation
|
Lake Elizabeth (top-ups as required to maintain water-quality targets) | - Maintain habitat for translocated Murray hardyhead
- Support submerged salt-tolerant aquatic plant assemblage and a high diversity of waterbirds
|
Lake Murphy (partial fill in autumn/winter) | - Promote the growth of a variety of vegetation communities (including recently planted juvenile river red gums) to support waterbird and frog feeding and breeding habitats
|
McDonalds Swamp (fill in spring and provide top-ups if required to support bird breeding) | - Increase the variety of vegetation communities by supporting the survival and growth of juvenile river red gums and reducing the spread of tall marsh
- Facilitate early plant germination and provide suitable conditions for winter frog breeding
|
Round Lake (top-ups as required to maintain water-quality targets) | - Maintain habitat for Murray hardyhead
- Maintain suitable waterbird habitat
|
Wirra-Lo wetland complex (top-ups as required to support a mosaic of wet and dry habitat) | - Rehabilitate river red gum and a variety of aquatic vegetation communities, providing suitable habitat for the growling grass frog and a high diversity of waterbirds including brolga
- Provide habitat for water-dependent animals
|
Wetland drying |
Hird Swamp, Richardsons Lagoon | - Not to be actively watered in 2018–19
- Seasonal drying helps to maintain the health of existing trees in the bed of the wetlands
- The drying phase of Hird Swamp will help to manage tall reed vegetation and promote herbland species
|
1 Infrastructure projects for Guttrum and Benwell forests are being assessed as part of the Sustainable Diversion Limit Offset component of the Basin Plan. Until works are approved and completed, only semipermanent wetlands that can receive water pumped from the River Murray will be considered for watering.
