National Cabomba map Draw down in Miriam vale... Mildura Victoria- - PowerPoint PPT Presentation

National Cabomba map

Draw down in Miriam vale...

Mildura Victoria- Cabomba

Mildura during drawdown-6 x months after re-filling still no cabomba

Lake Benalla - Victoria

Lake Benalla pre drawdown

After draw down

Earth works to minimize ‘puddles’

Lake Benalla, benthic blanket during draw down

Lake Benalla after re-filling... DPI Vic photos

11 Regeneration experiment  Questions  What is the regeneration potential of cabomba after a winter drawdown?  Does this vary with exposure status and weed mounds?

12 Regeneration experiment Exposed dry

13 Regeneration experiment Exposed saturated weed free (i.e. weed mound absent).... Fragment present.

14 Regeneration experiment Exposed saturated weed mound

15 Regeneration experiment

16 Regeneration experiment After 90 days

17 Regeneration experiment  Results 300 crowns sprouted stems sprouted No. of propagules m -2 250 200 150 100 50 0 ED ESWF ESWM ED Exposed dry ESWF Exposed saturated weed free ESWM Exposed saturated Weed mound

18 Stem and crown viability  After 70 days of exposure: • 95% of stems under mounds were viable where substrate remained saturated 20% where sediment was ‘dry’ • • 40% of crowns viable regardless of substrate being dry or wet

19 Regeneration experiment  Conclusion 1. Cabomba control was poor?? But wait…

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Why has the cabomba gone? Floods? 1. Lower light due to the high water and turbidity.  Less carbohydrate reserves at the end of the 2010  drawdown because of the recovery required after the 2009 drawdown. Dislodgement of damaged cabomba  Deposition of sediment on top of the cabomba  2. Multiple stressors 3. Would the cabomba decline have occurred with floods but not drawdown?

Key findings Winter drawdown works for control, under certain 1. circumstances: Repeated drawdowns a. Poor growth conditions after refilling b. Likely to hold for herbicide application too c. Active monitoring program (abundance and viability), 2. allows us to plan next steps (adaptive management) Change from control / protection of downstream to 1. eradication Understand recolonisation 2. Develop site specific control programs 3.