The Snowy Mountains Scheme has affected the ecology of Snowy Mountain rivers and streams. The Snowy Water Inquiry identified the need to increase flows to the Snowy River below Jindabyne and the Snowy montane rivers.

The NSW Office of Water is required to assess the ecological response of the increased flows to these waterways. The Office of Water Snowy Flow Response Monitoring and Modelling program has been established to assess the changes in river conditions that could be attributed to the increased flows. The key river attributes assessed include riverflow, geomorphology, water quality, plants, water bugs and fish.

The Office of Water also undertakes studies to assist in:

  • interpretation of the results from the main program
  • filling key information gaps
  • development of future environmental water allocations, including the generation of decision support tools for water management decisions.

A tour of the Snowy River

Take a trip down the Snowy River from the unregulated montane reaches via Guthega Dam, Island Bend Dam and Jindabyne Dam to the river mouth at Marlo.

The following presentation contains a series of photographs taken at key locations along the Snowy River by staff from the NSW Office of Water and the former Southern Rivers Catchment Management Authority (now Local Land Services).

Snowy River below Jindabyne

Following construction of the Snowy Mountains Scheme between 1955 and 1967, flows in the Snowy River have been severely altered, with less than one per cent of mean annual natural flow being recorded in the river at Jindabyne, or four per cent of mean annual natural flow as measured at Dalgety.

To improve river health, water has been released to the Snowy River via the Mowamba River (2002-2006) and/or Jindabyne Dam (2006-2010). Dependent on water savings in the western rivers of the Murray-Darling Basin, it is anticipated that up to 21 per cent of mean annual natural flow will be released to the Snowy River.

The Mowamba River weir

Mowamba River weir

The Mowamba River is an upper snow melt tributary of the Snowy River and is regulated by a weir. Environmental flows were released to improve the ecological conditions of the Snowy River, however the apparent lack of recovery has raised concern over the role of the weir acting as a barrier to the downstream migration of invertebrate fauna during environmental flows.

Snowy montane rivers

The increased flows to the Snowy montane are specified in the Snowy Water Inquiry Outcomes Implementation Deed and the Snowy Water Licence (Schedule 3, Part 5, Table 1).

Increased flows are to occur from five montane river release points:

  • Murrumbidgee River at Tantangara Dam
  • Goodradigbee River at Aqueduct
  • Geehi River at Geehi Dam
  • Snowy River at Gungarlin
  • Snowy River at Perisher/Rams Flat.

When the water becomes available these increased flows will be the equivalent to 118 gigalitres per year. Like the Snowy River below Jindabyne, these releases are also dependent on water savings in the western rivers of the Murray–Darling River.

The first stage of increased flows have commenced in the Goodradigbee River and the Murrumbidgee River below Tantangra Dam. The NSW Office of Water has commenced ecological field studies in some of these montane river systems.

Montane flow releases

Studies into the effect of the flow releases are detailed in the following fact sheet below.

Reports

Journal articles

Brooks A.J., Russell M., Bevitt, R. and Dasey M. (2011). Constraints on the recovery of invertebrate assemblages in a regulated snowmelt river during a tributary-sourced environmental flow regime. Marine and Freshwater Research 62, 1407-1420.

Hydraulic modelling animation

The animation shows modelled river flows for the spring 2010 environmental flow release to the Snowy River downstream of Dalgety. The animation was derived from hydraulic modelling as part of the Snowy Flow Response Monitoring and Modelling Program.

Spring 2010 flow release

Studies into the effects of the flow releases are detailed in the following reports:

Flow releases 2002-2005

Information sheets discussing the response to flow releases between 2002 and 2005 are listed below: