Lower Lakes, Coorong and Murray Mouth


Combining all water requirements for the Lower Lakes, Coorong and Murray Mouth



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Combining all water requirements for the Lower Lakes, Coorong and Murray Mouth


The future aim of LLCMM icon site managers will be to achieve as many of the above-listed flow targets as possible for the Lower Lakes and Coorong, in any given year. As more environmental water is incrementally available to the icon site, more targets can be met, and a greater ecological outcome achieved.

The following is based on the above discussion, and is a summary of targets to be achieved in priority order on an annual basis, as more water becomes available to the icon site:

• Lake levels are maintained above 0 m AHD to prevent exposure of acid sulfate soils.

• Lake levels are maintained within the seasonal operating levels.

• Fishways are operated year-round.

• Attractant flows are provided adjacent to fishways, and a limited estuary achieved in Boundary Creek.

• Minimum annual flow from the barrages required to achieve salinity target of <1,000 EC in Lake Alexandrina (650 GL+).

• Minimum annual flow required to keep the Murray Mouth open (730 - 1,090 GL).

• Flows of at least 2,500 GL over two years to prevent the Coorong existing in a degraded ecosystem state.

• Flows of 6,000 – 10,000 GL in a year to achieve a healthy Coorong ecosystem state.

Note that more specific information about barrage operation is provided in Chapter 4 - Water Delivery.

Table : Environmental water requirements of the Murray Mouth and Coorong to achieve icon site ecological targets



TLM Objective (M/F/B)

Target

Biota

Optimum salinity (ppt)*

Preferred Annual Volume (GL)

Frequency

Duration & Timing

B

Maintain or improve bird populations in the Coorong

Waders

60 - 100 ppt South Lagoon

6,000

10,000


1 in 3

1 in 7


 Refer hydrograph (Table 5)

Fish-eating birds

60 - 100 ppt South Lagoon

6,000

10,000


1 in 3

1 in 7


 Refer hydrograph (Table 5)

Water fowl (herbivorous)

60 - 100 ppt South Lagoon

6,000

10,000


1 in 3

1 in 7


 Refer hydrograph (Table 5)

M, F

Maintain or improve recruitment success of diadromous fish in the Coorong

Fish requiring both marine and freshwater habitats

fresh - marine

52 GL fishway operation (min) + attr flows

1 in 1

 Year-round fishway operation

F

Provide optimum conditions to improve recruitment success of small-mouthed hardyhead in the South Lagoon

Small-mouthed hardyhead

60 - 100 ppt South Lagoon

6,000

10,000


1 in 3

1 in 7


 Refer hydrograph (Table 5)

F

Maintain or improve populations of black bream, greenback flounder and mulloway in the Coorong

Black bream, greenback flounder, mulloway

fresh – marine: maintenance of a salinity gradient is the key requirement

6,000

10,000


1 in 3

1 in 7 


  Refer hydrograph (Table 5)

M, F, B

Maintain or improve invertebrate populations in mudflats in the Coorong

Mudflat invertebrates, waders

brackish - marine

6,000

10,000


1 in 3

1 in 7 


 Refer hydrograph (Table 5)

M, B

Facilitate frequent changes in exposure and submergence of mudflats in the Coorong

Mudflat invertebrates, waders

N/A

Murray Mouth open (730-1,090 GL)

1 in 1 

 Diurnal tide ratios met

B

Maintain habitable sediment conditions in the Coorong

Mudflat invertebrates, waders

N/A

N/A

N/A 

 N/A

F

Maximise fish passage connectivity between the Lower Lakes and Coorong

Fish requiring both marine and freshwater habitats

N/A

52 GL fishway operation (min) + attr flows

1 in 1

 Year-round fishway operation

F, M

Maximise fish passage connectivity between the Coorong and the sea

Fish that move between the Coorong & ocean, e.g. diadromous fish, mulloway, yelloweye mullet & greenback flounder.

N/A

Murray Mouth open (730-1,090 GL)

1 in 1

Diurnal tide ratios met

F, B, M

Maintain or improve Ruppia megacarpa colonisation and reproduction

Ruppia megacarpa

0 - 19 ppt North Lagoon for recruitment

6,000

10,000


1 in 3

1 in 7


  Refer hydrograph (Table 5)

F, B, M

Maintain or improve Ruppia tuberosa colonisation and reproduction

Ruppia tuberosa

60 - 100 ppt South Lagoon

6,000

10,000


1 in 3

1 in 7


 Refer hydrograph (Table 5)

F, B, M

Establish and maintain a variable salinity regime with >30% of area below sea water salinity concentrations in estuary and North Lagoon

Ruppia megacarpa, diadromous fish, mulloway, yelloweye mullet and greenback flounder, benthic invertebrates.

< 35 ppt in 30% of area of estuary and North Lagoon

Modelling required - annual volume will vary depending on starting conditions’

Modelling required - annual volume will vary depending on starting conditions’

Modelling required - annual volume will vary depending on starting conditions’






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