Mowamba and Jindabyne release flexibility

Investigation into delivering water for the environment for the Snowy River via the Mowamba River and options for more flexible delivery.

The Snowy Water Licence sets out Snowy Hydro Limited's rights and obligations for managing and releasing water in the Snowy River system and must be reviewed every 10 years. The latest review included actions relating to the delivery of water for the environment in the Snowy River.

Action 7 investigated the delivery of water for the environment via the Mowamba River to the Snowy River. Currently, the Mowamba River has its flows diverted to Lake Jindabyne.

Action 8A was to investigate more flexible delivery options for Snowy River Increased Flows to achieve better environmental outcomes. All Snowy River Increased Flows are currently delivered from Jindabyne Dam. The delivery plan for these flows is determined at the start of the water year (1 May), with minimal ability to alter delivery timing and rates in response to changing conditions.

Snowy Independent Scientific Expert Panel

In 2021, to address Actions 7 and 8A, the NSW Department of Climate Change, Energy, the Environment and Water engaged 3 independent experts to investigate the environmental effects of both the Mowamba release options and more flexible delivery options for Snowy River Increased Flows:

  • Dr Bruce Chessman, aquatic ecologist
  • Professor Ian Rutherfurd, fluvial geomorphologist
  • Professor Simon Mitrovic, algal and food web ecologist, Professor of Freshwater Ecology, University of Technology, Sydney.

For Action 7 – Mowamba River, the Panel recommended:

  • Mowamba River flows be allowed to pass Mowamba Weir to the Lower Mowamba River and the Snowy River.
  • Mowamba Weir be removed (as the preferred method for achieving the above recommendation).

For Action 8A – flexibility options for the delivery of Snowy River Increased Flows, the Panel recommended:

  • Allowing Jindabyne Dam releases to be synchronised with the flow in the Thredbo River or another naturally flowing reference river.
  • Allowing changes in flows within the year to respond to environmental conditions.
  • Allowing intra-day variability (changing release rates during the day so flows are not held constant for 24 hours).
  • Allowing the carryover of Snowy River Increased Flow allocations between years.

These recommendations were based on the expected environmental outcomes that could be achieved from each option.

Further work

The department will now work with Snowy Hydro Limited and other government agencies, including the Commonwealth and Victoria, to assess the feasibility and costs of releasing water via the Mowamba River (including the removal of Mowamba Weir) and of the recommended increase in flexibility options for the delivery of Snowy River Increased Flows.