Reinstatement of Lake Condah

Lake Condah forms a key part of the recently declared “Budj Bim National Heritage Landscape”, and is identified as a Wetland of National Significance, mainly based on cultural and ecological grounds. During the 1950s, Lake Condah was effectively cut in half and drained as part of the major engineering works to drain the Wallacedale and Condah Swamps north of Lake Condah. Since that time Lake Condah has not retained water other than during flood events, and even then flood waters are lost quickly from the lake because of the drain. The drain has effectively stopped seasonal inundation patterns at Lake Condah and led to a deterioration of ecological values at the site.

The lake itself has important cultural heritage values and is renowned for the unique eel trap system that indigenous communities employed therein.

The project objective was to reinstate the lake by installing a weir across the outlet drain and an outlet water regulator that will allow environmental flows to be provided downstream. Opportunity for fish and eel passage was also to be provided in accordance with that available during natural conditions (i.e when the lake is spilling).

Alluvium proposed an alternative to the traditional weir design, by designing a low gradient rock chute incorporating a low flow channel for fish passage. The 3 metre high, 100 metre long structure used rock in keeping with the rock that naturally outcrops at the site. The environmental flows are provided by a bypass pipe installed on the right bank, together with an inlet and outlet structure that automatically monitors and maintains flow at a designated value.

The design gave high consideration to the environmental and cultural sensitivities as well as technical requirements in determining access, construction techniques, and final appearance of the structural components. In addition to developing the concept and detail designs, Alluvium provided input and site inspections through the construction phase, working closely with the contractor.

The Lake Condah project was awarded the Victorian ‘Earth Award’ for category one, at the Construction Contractors Federation (CCF) annual awards in 2010.