Page 152 - VEWH Seasonal Watering Plan 2020-21
P. 152

 4.2 Glenelg system
Table 4.2.1 Potential environmental watering actions and objectives for the Glenelg River (continued)
 Potential environmental watering action
  Functional watering objectives
  Environmental objectives
  Winter/spring fresh in reach 1b (one to five freshes of 250 ML/day for one to five days during June to November/Big Wet to Fattening Up*)
    • Wet benches to improve the condition of emergent vegetation and maintain habitat diversity
• Provide adequate depth for fish passage and cue fish movement
• Provide triggers for platypus burrow selection
• Scour sand from pools to improve the quality of fish habitat
• Wet vegetation in the river channel and on the channel benches to support recruitment and growth
               Winter/spring fresh in reach 2 (one to five freshes of 300 ML/day for one to five days during June to November)
   Winter/spring low flow in reach 1a (60 ML/ day or natural during June to November)
 • Maintain water quality for fish and waterbugs
• Wet aquatic vegetation to maintain its condition and prevent encroachment by terrestrial species
• Maintain shallow-water habitat for fish, waterbugs and platypus
           Winter/spring low flow in reach 1b (100 ML/day or natural during June to November/Big Wet to Fattening Up*)
 Winter/spring low flow in reach 2 (160 ML/ day or natural during June to November)
 Winter/spring low flow in reach 3 (400 ML/ day or natural during July to December)
 • Wet benches to increase habitat and allow widespread fish passage and keep the estuary mouth open (based on estuary mouth flows)
        * The six seasons of Gunditjmara country match to reach 1b watering, as Figure 4.2.2 shows.
Scenario planning
Table 4.2.2 outlines the potential environmental watering and expected water use under a range of planning scenarios.
The highest priority under all conditions is to provide summer/autumn low flow in reach 1b and reach 2 to maintain connectivity and water quality between pool habitats above Casterton. This is the only flow that is expected to be delivered under the drought scenario.
Increased water availability under dry, average and wet scenarios will allow summer/autumn low flow to be delivered to reach 1a to provide additional swamp habitat and connection for native fish and frogs, and summer/ autumn freshes may also be delivered in reaches 1b and 2. These freshes are a high priority as they provide a cue for fish movement, allow native fish and platypus to disperse and wet streamside vegetation.
Under dry and wet conditions, delivering summer/autumn freshes in reaches 1a and reach 3 are a high priority to increase the habitat availability for native fish and platypus to move throughout the river system. Under average and wet conditions, delivering winter/spring low flow in reach 1a is a high priority, to support swamp habitat for native fish and frogs because it receives little natural flow even during wet years.
Delivering winter/spring freshes in reaches 1b and reach 2 is a high priority in the average scenario, to trigger native fish movement and platypus burrow selection in years when breeding is likely. Providing winter/spring low flow in reach 1b under wet conditions will increase habitat for native
fish and platypus, which will also help breeding success. The magnitude and/or duration of some freshes may be increased in the average and wet scenarios to extend the benefit of specific events further downstream.
   150 | Victorian Environmental Water Holder | Seasonal Watering Plan 2020–21






































































   150   151   152   153   154