Birchs Creek rises in the ranges north-east of Ballarat and flows north-west through Newlyn and Smeaton before joining Tullaroop Creek near Clunes. The target reach for environmental water is reach 3 because it contains the vulnerable river blackfish population, and most irrigation supply is diverted before the reach.
Birchs Creek is part of the Bullarook system which has two small storages — Newlyn Reservoir and Hepburn Lagoon — that fill and spill during winter or spring in most years with average or above-average rainfall.
Environmental water is held in and delivered from Newlyn Reservoir. The VEWH is allocated 100 ML of water on 1 December each year unless seasonal determinations of high-reliability water shares in the Bullarook system are less than 20 percent. Any unused environmental allocation from 1 December can be carried over into the first five months of the following water year (that is, from 1 July to 30 November), but if Newlyn Reservoir spills during these months the volume held in carryover is lost. Any water remaining on 30 November is forfeited. When seasonal determinations are less than 20 percent, the VEWH is not allocated water and the system's resources are shared equitably to protect critical human and environmental needs.