Page 254 - VEWH Seasonal Watering Plan 2020-21
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  Potential environmental watering action
  Functional watering objectives
  Environmental objectives
 Autumn fresh (one fresh up to 6,000 ML/day for two days between March and April in reaches 4 and 5)
• Encourage the germination of new seed on the lower banks and benches
• Improve water quality by reducing turbidity and mixing stratified water
• Flush fine sediment from hard substrates to allow new biofilm growth and to improve food and habitat for macroinvertebrates
               Flows should not exceed 1,000 ML/day (for more than 20 consecutive days, with a minimum of seven days between pulses in summer/autumn in reaches 4 and 5)
• Maintain for more than one season a littoral fringe of emergent or semi- aquatic plants
• Provide slow-flowing littoral habitat for small-bodied fish and macroinvertebrates
                    5.4 Goulburn system
Table 5.4.1 Potential environmental watering actions and objectives for the Goulburn River (continued)
 Scenario planning
Table 5.4.2 outlines the potential environmental watering and expected water use under a range of planning scenarios.
In 2020–21, the focus of water for the environment in
the lower Goulburn River will be on vegetation recovery
to improve the condition of the lower banks that have
been damaged by high IVTs in summer/autumn in recent years and to help offset the impact of future IVTs. Under
all scenarios, providing year-round low flow is the highest priority under all scenarios. This flow provides habitat for fish and macroinvertebrates and helps the vegetation to recover. Goulburn-Murray Water generally diverts a proportion of natural high flow from Goulburn Weir into the Waranga Basin. These operational transfers cause flow rates in the lower Goulburn River to drop rapidly after a natural high- flow event. Water for the environment is used when required to slow the recession of natural spills at Goulburn Weir, to reduce the risk of bank slumping and provide a more natural flow pattern for native fish. The highest environmental watering priority in reach 1 will be to maintain minimum low flow outside the irrigation season, to maintain habitat for small-bodied native fish, aquatic vegetation and waterbugs.
Delivering a winter/spring fresh followed by five to six weeks of low flow is a high priority in 2020 under dry and average scenarios, to aid vegetation recovery. These flows are expected to occur naturally under a wet scenario and are planned under a drought scenario as an additional priority.
A focus this year will be on timing environmental water deliveries alongside unregulated events and tributary inflows. Ongoing monitoring suggests that unregulated inflows carry more plant seed, nutrients and sediments that are beneficial to the lower Goulburn River.
A winter fresh is included under average and wet scenarios to enhance environmental objectives that cannot normally be achieved under drier scenarios. A spring/summer fresh will also be considered under average and wet scenarios to cue golden perch spawning, but this watering action will not be delivered if it is likely to impact the recovery of bank vegetation. If summer low flow targets are met (that is, if IVTs are not too high), an autumn fresh may be delivered in March or April 2021 to maintain bank vegetation and allow new seeds to germinate.
Carrying over water to meet minimum low flow objectives in July 2021 to September 2022 is an important consideration under drought, dry and average scenarios.
   252 | Victorian Environmental Water Holder | Seasonal Watering Plan 2020–21

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