The Tarago River has its headwaters in the Tarago State Forest and it flows into the Tarago Reservoir at Neerim. Downstream of the reservoir, the river flows close to the town of Rokeby before meeting the Bunyip River (of which it is a major tributary) at Longwarry North. The downstream reach towards Western Port Bay supplies many irrigators in the catchment.
Water available under the Tarago environmental entitlement is stored in and released from Tarago Reservoir. Reach 2 is the target reach as it has high ecological value with a diversity of native fish and patches of native fringing vegetation. Deliveries to reach 2 often result in the desired flows in reach 6 (see system map below).