State Water Corporation / Removal of Trees at the Proposed Lake Wetherell Fuse Plug, Menindee - SWCDoc13/32282

Lake Wetherell is one of the lakes in the Menindee Lake System, which is located on the Darling River, approximately 200 kilometres upstream of the junction of Darling and Murray Rivers, and nearly 10km north-east of Menindee.

There are four main lakes in the system including Lake Menindee, Lake Cawndilla, Lake Pamamaroo, and Lake Wetherell. Lake Wetherell is one of the uppermost lakes and is formed by the combination of a block dam in the Darling River, the Lake Wetherell Outlet Regulator, the Menindee Main Weir and a series of levees. Lake Wetherell plays a pivotal role in the operation of the system since it diverts water into all the downstream lakes via the Lake Pamamaroo inlet regulator.

The Lake Wetherell East levee extends from the Main Weir to sand hills near Windalle homestead and incorporates a fuse plug spillway. The role of this existing fuse plug (constructed in the late 1950’s) has been to safely divert Darling River flood flows that are greater than the capacity of the Main Weir.

The existing fuse plug has only operated on one occasion, in 1974. On this occasion, substantial problems were realised with scouring and difficulty in stemming the flow once activated. Given the very close proximity of the fuse plug to the river, erosion progressed through the fuse plug to within only a couple of metres of the Darling River channel.

This raised concern in regard to formation of a gully, which could lead the river system to branch out into the flood plain. Therefore, there was a need for reviewing the fuse plug arrangement and its operation to minimise erosion and also to ensure that the design flood requirements were met.

State Water has undertaken optimisation studies for a new fuse plug arrangement in order to minimise erosion along the river bank, and has proposed to relocate the fuse plug further downstream of Three Mile Creek. The crest length of the proposed fuse plug is 1,500 metres.

The scope of works under this contract includes the removal and disposal of trees immediately upstream of the proposed fuse plug to clear the water passage, once triggered.

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10 Weeks