Page 231 - VEWH Seasonal Watering Plan 2020-21
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Scenario planning
Table 5.2.13 outlines the potential environmental watering and expected water use under a range of planning scenarios.
In the event of ongoing dry conditions, a modest watering program is proposed for the 2020–21 year. The highest priority under all scenarios is to ensure water and salinity levels at Brickworks Billabong, Lake Hawthorn and Koorlong Lake are suitable to protect the endangered Murray hardyhead. Lake Hawthorn and Koorlong Lake
will likely require managed environmental water deliveries under all scenarios, but natural floods are likely to meet the required watering regime at Brickworks Billabong under
a wet scenario. Maintaining varying levels of permanent water at these sites also provides shallow-water habitat for wading, feeding and loafing by small wading bird species and migratory birds.
Under dry and average scenarios, additional priority sites include Robertson Creek, Neds Corner Woolshed Creek, Margooya Floodplain Wetland and the Bidgee lagoons (see the additional information below). The target water levels and volumes delivered to these sites may vary under each scenario depending on the available water, local rainfall and assessed environmental conditions. The rationale for watering these sites in 2020–21 is described below.
Robertson Creek contains black box woodland and shrubby understory communities, which are currently in poor condition and considered to have a low resilience to ongoing drought. Watering at this site aims to improve the condition of these vegetation communities and help protect nearby areas of cultural significance.
Watering at Neds Corner Woolshed Creek in 2019–20 had a very positive effect on native plants and animals at the site. Follow-up watering in 2020–21 will help improve the condition of the low herb communities at the wetland base and the large old river red gums, and it will build their resilience.
Under dry and average scenarios, environmental water may be pumped from the Murray River into the Margooya floodplain wetland in autumn 2021 to improve the health of river red gum that haven’t been wetted since the 2016 floods. This watering will support Aboriginal cultural objectives at the site.
The Bidgee lagoons support two water-dependent ecological vegetation classes (floodplain grassy wetland and riverine chenopod woodland) that are classified as endangered in the Murray Fans bioregion. The lagoons have received water four times in the last 10 years, but the duration of these natural events was relatively short and did not deliver the environmental benefit expected of longer- duration events. Vegetation in some parts of the lagoons
is in moderate condition, but vegetation in other areas is in poor condition. Targeted environmental watering is planned under dry and average scenarios in 2020–21 to improve the condition of vegetation communities across the whole site.
Under a wet scenario, many wetlands across the lower Murray floodplain are likely to be watered by natural floods and local rainfall. The only high-priority sites that are likely to require environmental water to meet their recommended watering regime under wet conditions are Lake Hawthorn, Koorlong Lake, Robertson Creek and Burra Creek South proper.
Burra Creek South proper has received water only twice
in the last 10 years, with environmental water delivered in 2013–14 and 2014–15; and it did not receive any flood water in 2016. The site contains lignum, red gum and black box communities and was last observed in 2018 as being in moderate condition. However, due to persistent dry conditions after 2016, the site is at risk of deterioration. A fill in spring would improve vegetation condition and provide habitat for waterbirds and waterbugs.
If more water is available under average or wet conditions, it may be used to improve the condition of other sites on the lower Murray floodplain considered a lower priority. Under average conditions, extra water may be used at Robertson Wetland and Fishers lagoons. Under wet conditions, extra water may be used at Lake Powell and Lake Carpul. Watering these sites in 2020–21 if the opportunity arises will reduce the need to water them in the next one to two years if dry conditions return.
5.2 Victorian Murray system
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