To maximise the potential benefit of the proposed environmental regulator for Chowilla Creek, it will be necessary to operate complementary structures in conjunction with weir pool raising at Lock 6. Pipeclay Creek Weir and Slaney Creek Weir in particular, will be used to ensure delivery of flow into the anabranch and to control the rate of water level rise and fall. Even in the absence of a downstream environmental regulator, these structures will be important for managing flows through the anabranch, increasing in-stream variability, and delivering ecological benefits on a local scale. The new structures will enable the delivery of pulse flows down Pipeclay and Slaney Creeks; this is expected to generate native fish spawning cues. In their current condition, neither of these structures can be safely or efficiently operated.
The modifications to Pipeclay and Slaney Creek Weirs will involve:
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Replacing the stoplogs with spindle gates
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Installing a vertical slot fishway for small fish
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Installing a denil fishway for large fish
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Undertaking repairs to the downstream aprons
Bank E was replaced in 2007 with a new submerged rock ramp fishway. The old bank was in a state of disrepair, did not provide fish passage between the river and anabranch and its condition, and subsequent high risk of erosion and failure limited opportunities to enhance river levels using Lock 6 and other local structures. The new submerged rock ramp fishway maintains flow into the anabranch, provides fish passage and enables greater opportunities for weir pool raising for environmental benefit.
Complementary works form a major component of the overall Chowilla Icon Site Integrated Natural Resources Management Project and include:
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construction works at key flow control sites including Pipeclay and Slaney Creek Weirs, Bank E and Boat Creek Bridge to enable improved management of flows to the Chowilla anabranch;
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works at Werta Wert Wetland and other key wetland sites that facilitate the environmental enhancement of the Chowilla floodplain and complement the long-term management actions proposed for Chowilla; and
- the feasibility of complementary floodplain and wetland watering opportunities particularly in the eastern section of the floodplain;
URS (2006). Concept Design for Weir Modification and Fish Passage at Various Chowilla Floodplain Structures. Report for the DWLBC (20.2Mb)
DWLBC (2007) Assessment of the impact of the operation of the modified weirs at Pipeclay and Slaney creeks
Smith and Schultz (2004). Register of Structures at Chowilla. Report for the DWLBC (50Mb)