Glenelg system

The regions experienced below-average rainfall for much of 2018–19. Several natural high-flow events in July and August 2018 met many of the environmental flow objectives for those months, but inflows to storages were well-below average between September 2018 and April 2019. The dry conditions meant the VEWH only received a portion of allocation against its Wimmera-Glenelg environmental entitlement. As of March 2019, the VEWH had received 55 percent allocation for the year, but the total volume of available water for the environment was supplemented by system reserves that were carried over from 2017–18. Passing flows were suspended during the high-flow events in July and August, to reduce the flood risk to communities downstream of Rocklands Reservoir, and water accumulated at those times was used to help meet environmental objectives in spring.

A combination of natural inflows and managed environmental flows maintained continuous flow between Rocklands Reservoir and the Glenelg estuary for most of 2018–19. The only disruption to this flow occurred in March 2019, when releases were suspended for two weeks to allow maintenance works on headworks infrastructure, carp screen cleaning and an upgrade of the Sandford fishway.

Water for the environment was used throughout the year to provide opportunities for native fish, platypus and crayfish to disperse between river reaches and to access a variety of habitats throughout the system. Spring flows also watered riparian vegetation including recently recruited seedlings, and helped move nutrients, leaf litter and small branches from the riverbank into the river channel where they can provide food, energy and habitat for aquatic biota. Low flows delivered during 2018–19 maintained the quality and quantity of water in riffles and pools along the river, to provide suitable habitat for waterbugs, native fish and other aquatic species. Occasional freshes reduced salinity and water temperature and increased dissolved oxygen concentrations in deeper pools along the river system.

Hot and dry conditions through summer and autumn increased seepage and evaporation losses, which meant that some target low flows did not achieve intended flow rates in downstream reaches. Fish monitoring conducted as part of the Victorian Environmental Flows Monitoring Assessment Program (VEFMAP) in autumn recorded a nationally threatened Australian grayling in the Glenelg River below Casterton (reach 3) for the first time in 122 years. The presence of Australian grayling and other fish species that rely on specific flows in freshwater reaches and the estuary indicates that managed environmental flows in the Glenelg River are helping to meet the requirements of native fish.

In late November 2018, water for the environment was delivered over 12 days to reach 0 from Moora Moora Reservoir. This is the second time water for the environment has been released from Moora Moora Reservoir, and the event was monitored to understand how water can be delivered from the reservoir to maintain and improve remnant plant and animal populations. Temporary gauges installed in reach 0 showed that the released water spread along several natural flow paths and did not contribute any detectable flow at the end of the reach.

Table 2 shows the partners, stakeholder organisations and individuals with which Glenelg Hopkins CMA engaged when preparing the Glenelg system seasonal watering proposal.

Seasonal watering proposals are informed by longer-term regional catchment strategies, regional waterway strategies, environmental flow studies, water management plans and other studies. These incorporate a range of environmental, cultural, social and economic perspectives and longerterm integrated catchment and waterway management objectives. For further details, refer to the Glenelg Hopkins Regional Catchment Management Strategy and Glenelg Hopkins Waterway Strategy for further details.

Table 2 Partners and stakeholders engaged in developing the Glenelg system seasonal watering proposal