The highly anticipated and much debated Lake Kepwari has started providing river flow for the first time this year, following an increase in rainfall last month.
The Collie River South Branch and its pools are now receiving water flow through the man-made lake following the driest winter since 2010.
Member for Collie-Preston Mick Murray joined members of Premier Coal at the lake to see the water flowing a week on from the heavy downpours that dropped more than 70 mm of rain in August.
Mr Murray said he was pleased to see the river flowing after an unusually dry winter which had delayed the south branch pools filling up.
"It's been a long time in the planning and now it's come to fruition despite many people doubting the engineers doing their job," he said.
"It's pleasing to see the pools themselves below this area have filled up and filled up so quickly. ... [the outlet] will be low enough to have the water flowing early and some years it will be flowing very, very fast."
Mr Murray said he would make every effort to have skiing in the lake in summer as the state government works through legal and safety matters.
A Premier Coal spokeswoman said the health of the river would improve now the outlet works have been completed and the river has reached capacity
"The flow through of the Collie River South Branch through Lake Kepwari improves the water quality in Lake Kepwari, particularly in terms of elevating pH, increasing nutrients and reducing metal concentrations," she said. "The lake also helps to improve water quality in the Collie River South Branch by reducing the nutrient load in the river."
While originally planned as a closed catchment, extensive research and investigation over the past seven years saw the plan modified to divert the Collie River back to its original path back through the mine void, which was approved by the shire and state government.
Since the decision was made to divert the river, the lake has been under scrutiny from locals over the health of the river system. The shire even approved a motion to write to the state government in an effort to pressure the state to prioritise the health of the river system ahead of the lake.