The Glenelg River supports a wide range of flow-dependent environmental values including rare and threatened plants and animals. Its diversity results from its range of landforms and climate conditions and its connection with the estuary.
The Glenelg River is an integral part of the Wimmera–Mallee headworks system, which supplies towns and properties across the Western Region. The river is regulated at Moora Moora Reservoir and Rocklands Reservoir. Water is also diverted from the Glenelg catchment to the Wimmera catchment by the Moora Moora channel and the Rocklands–Toolondo–Taylors channel and at three weirs on the upper Wannon River. Environmental water is actively managed in the main stem of the Glenelg River below Rocklands Reservoir with passing flows rules in place for the upper Wannon River diversions.
Due to their high environmental value, the priority river reaches are from the Rocklands Reservoir to 5-Mile Outlet (reach 1a), 5-Mile Outlet to the confluence with the Chetwynd River (reach 1b) and from the Chetwynd River to the Wannon River (reach 2). Environmental water in the Glenelg system is released from Rocklands Reservoir for reach 1a via the reservoir wall outlet and for reach 1b via the 5-Mile and 12-Mile outlets, with through-flows delivering water to reach 2. The Glenelg River reach 3 and estuary also benefit from environmental water releases.
Although not managed for environmental needs, the Glenelg River above Rocklands Reservoir (reach 0) runs mostly through the Grampians National Park and retains significant environmental values. Further work is being undertaken to confirm the flow requirements of this reach. Work is also being undertaken to better understand the role that environmental releases from Rocklands Reservoir play in the health of the Glenelg River estuary (which is listed as a heritage river reach and has been nominated for listing under the Ramsar Convention).