Snowy Montane Rivers increased flows

The Snowy Water Inquiry Outcomes Implementation Deed (SWIOID) also provides for environmental releases into a number of high altitude (montane) rivers whose flows are significantly affected by the operation of the Snowy Scheme. These rivers and the initial target annual release volumes are:

• the Snowy River above Jindabyne Dam (59 GL)
• the Goodradigbee River (12 GL)
• the Murrumbidgee River below Tantangara Dam (27 GL)
• the Geehi River (20 GL).

Each release point results in a different amount of foregone generation for Snowy Hydro Limited for each megalitre of water that is released, with Snowy Hydro Limited required to forego generation up to a maximum of 150 gigawatt hours each year. Each year, the degree to which generation is foregone reflects the volume of water allocated to the Snowy River. If the full 212 GL target is available for the Snowy River, the full 150 gigawatt hours of generation will be foregone by Snowy Hydro Limited.

As the water is either re-regulated by the Snowy Scheme, or by water supply storages in the western rivers, additional water savings are not required to enable these releases.

However, all of the targeted release points required modification to the existing works to enable the releases to be made. This has been undertaken progressively as savings in the western rivers have increased, and foregone generation has increased. Releases are now occurring into most of the targeted montane rivers, although final release arrangements for the upper Snowy River near Guthega are still being developed.

2022-23 water year

Table 1. Outlines the 2022-23 annual targets for the Snowy Montane Rivers

Increased flows	Release location	SWIOID annual target (GL)	Adjusted implementation annual target (GL)	2022-23 annual volume
Murrumbidgee River @ Tantangara	Tantangara Dam	27	27	35.8
Goodradigbee River*	Goodradigbee Weir	12	12	12
Geehi River	Middle Creek Weir Strzelecki Creek Weir	20	17.5	20
Snowy River - Island Bend	Toolbar Creek Diggers Creek Weir	20	18.9	20
Snowy River - Perisher Range#	Falls Creek Weir and minor diversion structures	30	3.4	30

Snowy weirs

In the case were water is being released from small Snowy weirs, the long term average annual catchment yield is typically targeted. The flows will reflect the inflows to the upstream weir pool.

Upper Murrumbidgee River

In the Murrumbidgee River below Tantangara, the hydro-scaling approach is being implemented, but includes operational constraints of the dam infrastructure. Tantangara Dam is a large storage that can generally make releases as required each day, but there are greater operational constraints at Tantangara Dam than compared to Jindabyne Dam.

The proposed daily flow pattern attempts to include the key hydrological signals typical of a smaller mixed snowmelt - rainfall river system characteristic of the northern Snowy Mountains.

For details on the Snowy and Montane River Increased Flows releases from Tantangara Dam.

The details of these releases are located in the annual Snowy Montane Rivers Increased Flows (SMRIFs) strategy – see links below.