City of Ballarat contractors yesterday finished a project to gravity-feed stormwater from Ryan St, Brown Hill, to Lake Wendouree.

The stormwater will flow from a 47ha catchment area.

City of Ballarat sustainability director Ian Rossiter said it was expected to yield between 50 and 75 megalitres per year for the lake.

Construction on the project began in January, where specialist fittings connected the cast-iron main into an existing stormwater pipe, and new pits were built.

The option came from Ballarat engineering company TGM's senior hydraulic engineer Peter Tadgell, who has extensive knowledge of Ballarat's underground infrastructure.

At Ryan St, the pipe is about 13m higher than lake level, before it dips below lake level in Mair St.

Mr Rossiter said rainfall into the catchment would fill the low point of the Gong Gong drain until there was enough water to push it over the rise in Mair St and down to the lake.

He said the pipeline would eventually hold between three and four megalitres of water.

"With works being completed and rainfall forecast this weekend, it's only going to be a matter of days and weeks before we see water coming out.''

Currently, water from Pauls Wetland is not going into Lake Wendouree due to other piping works, but will shortly resume with the works nearing completion.

Mr Rossiter said it was predicted the lake would reach 900mm below full at its peak this year.

"What we've seen in recent years is the major gains in inflows don't start kicking in until spring; the lake is at its highest in November before it starts to decline over summer and autumn,'' he said.