Water flow control and improved water quality

Option 1 has some pros with dredging and planting native vegetation but if the existing spillway is retained exactly how it is, the water flow reaching the creek in Hallett Cove Conservation Park (HCCP) is still at too higher velocity. Erosion will continue and the creek will get carved out even further. The spillway needs to be modified so that the water slows down before travelling down the creek because at the moment the water freely flows through and gains momentum as it travels downstream. Otherwise, some of the water needs to be diverted out the side of the dam wall so the dam has time to empty out to a lower level before it fills up again. The diverter on the dam wall should be able to be manipulated as to maintain the water during seasonal changes (i.e. diverting water out in Winter but blocking water in during Summer).

The water quality needs to be improved so that carp aren't continuously degrading the water clarity. They are detrimental to the environment and the idea that people fish from the dam and possibly release fish into the dam for recreational purposes is illegal. People should be educated about the detrimental effects on the environment this behaviour has. If the carp were removed over time, eventually the water would be clearer, cleaner and would have a better chance at supporting native species, including frogs (which were previously found in the HCCP creek downstream), invertebrates and other native animals.

Any native revegetation is encouraged and will help soil stability and encourage native animals. Option 1 would be ok if the spillway was modified to reduce flow or a bypass was created to control the water levels of the dam and thus the existing spillway would suffice.


Option 2 is an ecologically advantageous option and encourages various native species to inhabit the area. As mentioned in the stage two draft, it would also help improve water quality which aligns with the conservation values of HCCP. Replacing the existing spillway with erosion protection would also be an ideal option to minimise further erosion downstream. As long as sufficient levels of water were still directed downstream (the creek usually only dries out in Summer and small pools retaining water can be seen up to December) then it would be acceptable. If the bypass structure isn't underground or designed to be aesthetically pleasing, it may interrupt the ability to enjoy the area in it's natural state. The wetland still retains some water bodies and can help make the area attractive with appropriate native plants and through encouraging local wildlife such as birds to the area. The climate will continue to impact on the water levels and drying out in Summer should be expected.

Volunteer groups have done an extraordinary effort in trying to revegetate and maintain the stability of the creek in HCCP but erosion and water quality have hindered any efforts attempted. Previous plants that were put in were washed out to sea following weather events that caused the water to gush through the spillway and over the top of it. The water velocity needs to be controlled so that if high rainfall events occur again, the same thing doesn't occur. The weeds, pollutants and non- native fish creating sediment are all being washed into the conservation park and then into the gulf.This is completely adverse to the needs of the conservation park and efforts of the volunteers. The water quality needs to be improved so that native species may return to the HCCP creek. As mentioned, frogs and invertebrates used to be found in the creek but since the dam has become more polluted and erosion has washed away any revegetation efforts, they have since decreased or disappeared. The wetlands will help encourage native species and neighbours may be welcomed with a cacophony of frog sounds and birdlife. As mentioned though, there still needs to be enough water diverted downstream to the creek so that flora and fauna species can be encouraged and maintained.


In conclusion,

Option 1 has it advantages but only if the spillway is modified for controlled flows or a bypass is created to control water levels in the dam. Option 2 would be ecologically advantageous and would align with HCCP conservation values IF sufficient levels water flow was diverted downstream. Although the wetland is not a permanent water body, the native flora and fauna in the area would be aesthetically pleasing and further education about environmental benefits to the area and community should be encouraged. The climate is ever changing and droughts are a natural occurrence so it is not viable to expect the water will not dry up in periods of less rainfall. Planting native vegetation is outlined in both options and is strongly supported for the conservation value of HCCP, especially as seeds will be washed downstream.



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Consultation has concluded