Reach 1 of the Coliban River below Malmsbury Reservoir to Lake Eppalock can benefit from environmental watering. An important distinction between the Coliban River and other regulated Victorian systems is the lack of irrigation demand in the river. Therefore, the river below Malmsbury has lower-than-natural flows year-round and environmental water is needed to provide adequate flow during summer and autumn.
The VEWH does not have any environmental entitlements in the Coliban system, but passing flows can be managed to help mitigate some risks associated with critically low summer flow including low levels of dissolved oxygen. A small volume of Commonwealth environmental water is held in the system, but the high cost of delivery means there is no plan to use it in 2017–18.