Snowy Water Initiative
The Snowy Water Initiative was formally established in 2002 to achieve significant improvements in river health by releasing environmental water into the Snowy, upper Murrumbidgee, and upper Murray river systems. At the commencement of the Snowy Water Initiative, the NSW, Victorian and Commonwealth governments and Snowy Hydro Limited have invested $1.2 billion in water recovery infrastructure upgradees, water management and science to allow environmental water to be released to these Snowy water sources.
The Snowy Water Inquiry Outcomes Implementation Deed (SWIOID) 2002 is a legal instrument that the three partner governments entered into to give effect to the outcomes of the public Snowy Water Inquiry in 1998 and the corporatisation of the Snowy Scheme. The deed includes the water recovery targets for the Snowy, Murray and Snowy Montane Rivers Increased Flows programs.
Targets for the Increased Flows programs include returning the following volumes of water each year:
- Snowy River – 212 gigalitres (GL), or 21 per cent of the average natural flow
- Murray River – 70 GL
- Snowy Montane Rivers – up to the equivalent of up to 150 gigawatt hours of forgone electricity generation, which equates to up to 117.8 GL.
Water for Rivers was the joint government enterprise established to develop water efficiency projects and other measures, including licence purchases, to recover the water for the three Increased Flows programs.
The Water for Rivers enterprise completed its task of securing the 212 GL of licensed water entitlement from the western rivers in July 2012.
On completing a water efficiency project, the recovered water was converted into a water entitlement. These entitlements then receive water allocations into their water allocation accounts as available water determinations are made in each river system (i.e. from the location where the entitlement was recovered). The water in these accounts is then used to provide environmental releases for the Snowy, Snowy Montane and Murray Rivers.
While the 212 GL target of entitlements has been recovered for the Snowy River, this does not directly equate into volumes of water available for release into the Snowy River. Depending on water availability in any season, a licensed entitlement holder in the western rivers is allocated a proportion of their entitlement to use that year. In many years that may be 100 per cent of entitlement, but in drier or drought years that proportion may be significantly reduced. This means that the volume of water available may be significantly lower than the total of entitlements under very dry conditions.
Each year, the water allocated to the recovered or purchased water entitlements is used to supply water to the Snowy River, Snowy Montane Rivers and the Murray River. These water allocations are apportioned between the Snowy and Murray Rivers in a 2:1 ratio, until the Snowy River receives 140 GL and the Murray River receives 70 GL. All further savings beyond this point are then allocated to the Snowy River (target 212 GL). These annual volumes are known as Snowy River Increased Flows (SRIF) and River Murray Increased Flows (RMIF). The allocations to the Snowy Montane rivers is called the Snowy Montane Rivers Increased Flows (SMIRF).
A summary of the entitlements and allocations to the individual savings measures, the cumulative volumes that have been apportioned to the Snowy and Murray Rivers, and the volumes that were apportioned to repay the Mowamba Borrowings Account each year are shown in the Snowy Water Savings Summary Table - May 2014 (PDF 30kb).
Snowy River Increased Flows
In determining how to use the environmental water in the Snowy River, the three Governments agreed that the primary ecological objective would be achieved by storing and then releasing sufficient volumes to provide annual flushing flows. These high flows facilitate the improvement in the physical condition of the in-stream habitat by scouring and transporting sediment (i.e. primarily, sand, silt and clay). This primary ecological objective was identified as a high priority for the environment during the Snowy Water Inquiry. These high flows are important to improve river health. It is expected that as the river physically responds over time to the higher flows, the focus of the recovery process will transition to meet other secondary ecological objectives.
To date four flow strategies have been implemented in the Snowy River (SRIF) between 2002 and present.
Stage 1: 2002-2006 (Tributary releases – low allocation)
To provide flushing flows to improve habitat quality the outlet works at Jindabyne Dam were required to be upgraded. Construction occurred between 2003 and 2006. While this work was occurring, the initial three years of releases from 2002 to 2006 were made via a tributary release at the Mowamba Weir on the Mowamba River.
During the initial stages of the increased flows to the Snowy River, water was borrowed from the Snowy Scheme as the water savings had not yet been achieved. These releases from the Mowamba River occurred prior to the recovery of significant amounts of water entitlements. In effect, the water was borrowed in order to make the initial releases - see Case study. The stage occurred during a period of drought and low allocations.
The second stage involved making releases from the new outlet works from Jindabyne Dam, again during a period of historic drought conditions across south-east Australia.
During this stage, the overall volume was comparatively similar to stage 1, but the flow regime differed from the first stage, in that there was a reduction in daily flow variability.
Under the SWIOID, the Mowamba Borrowings Account must be repaid from water apportioned to the Snowy River (SRIF). Each year the first 38 GL of water was to be made available for environmental flows, and any additional water was to be used to repay the Mowamba Borrowings Account, up to a limit of 38 GL. Any further water apportioned to SRIF beyond these amounts was also available for environmental flows.
During the height of the drought, water allocations were only sufficient to provide the first 38 GL of environmental flows, and repay a portion of the Mowamba Borrowings Account. On 11 August 2010, the NSW, Australian and Victorian Governments agreed to provide an additional 56.3 GL in 2010-11 for higher environmental flows in the Snowy River. This agreement allowed the Mowamba Borrowings Account to be fully repaid, and an additional 24.2 GL of environmental flows to be released from Jindabyne Dam to the Snowy River. As a result, the total environmental flows to the Snowy River in 2010-11 exceeded 62 GL.
Stage 3: 2010-2013 (Jindabyne releases - single large spring pulse)
The third stage of releases occurred as more entitlements were generated from water savings projects, and the drought across south eastern Australia gave way to wetter conditions. This provided sufficient water savings for flushing flows to be made to the Snowy River.
The significant change in the operation of Jindabyne Dam occurred during this period, as the higher water allocations allowed the first large flushing flows to be released and the lake water level is now required to be held at higher levels to allow for the flushing flows. These flushing flows were designed to address the initial objective of the Snowy River recovery, which was to improve the in-stream habitat quality by re-introducing an annual spring flood.
These flows initiated the start of the physical recovery of the Snowy River habitat by scouring the riverbed of the stored sediment in the river channel, and improving habitat condition. These high flows were a significant event for the local community and landholders. An additional large release occurred in March 2012 (i.e. similar to the 2011 spring event) as a flood mitigation measure given the Lake Jindabyne was at full supply level.
However, the flushing flows typically consumed about 60 per cent of the annual water allocation and resulted in limited daily flow variability for the remainder of the year. Many of the other hydro-ecological targets could not be met during the remainder of the year.
The fourth stage of the environmental water releases commenced during the 2013-14 water year. This stage of the program is attempting to build on the previous release program by including high flows, but also increasing the daily flow variability for the entire water year.
The stage four strategy has the following broad objectives:
- To better reflect the hydrology of a Snowy montane river, including increasing the daily, seasonal and annual flow variability.
- To provide multiple high flow events to meet the primary ecological objective of habitat improvement.
- To fully utilise the infrastructure capability of Jindabyne Dam to provide variable flow rates.
- To provide complimentary tributary releases in Autumn to provide basal resources to stimulate the aquatic foodweb.
The flow pattern during this stage differs from previous years, as it better reflects the hydrological characteristics of a Snowy Montane River. The SRIF strategy includes higher flows over winter and spring, with five high flow events occurring in a water year. These events will have an eight hour pulse of high flow water to promote scour of the river bed which improves habitat. These five events include on primary event (the flushing flow) and four secondary high flow events.
- See an Overview of Stage 4 SRIF: a comparison of the five peak discharge events per year for SRIF targets Stage 3 and Stage 4 -2010 to 2016 (GIF, 10.52 KB)
- The annual peak SRIF target discharge is indicated by an * symbol.
Current water year: 2016-17
A revised operational target of 131.07 GL is to be released to the Snowy River during 2016-17 from Jindabyne Dam, which includes a base passing flow of 8.5GL. An additional 0.5GL of base passing flow will be delivered from the Mowamba Weir.
Additional to the surrogate river hydro-scaling approach, another trial release of water from the Mowamba River to the Snowy River will occur during May 2016 to provide carbon and to reduce a-seasonal water temperatures in the Snowy River.
The five winter-spring high-flow releases are:
|Release date||Volume (megalitres/day)|
|Thursday 16 June||2,115 megalitres/day*|
|Wednesday 17 August||2,236 megalitres/day*|
|Wednesday 7 September||2,536 megalitres/day*|
|Tuesday 20 September||3,079 megalitres/day*|
|Wednesday 5 October||8,109 megalitres/day*|
* These high flow events are expressed as an equivalent flow rate. The peak flow rate will occur for 8 hours so as to (i) mimic the flashy hydrology of the Snowy and to (ii) promote habitat improvement. These will occur from 7am to 3pm.
DPI Water will issue 'Rising River Alerts' to relevant media organisations a few days prior to each of the five release events.
- Strategy for Snowy River Increased Flows 2016-17 (PDF, 1522.44 KB)
- Current Water Year – Snowy River Daily Releases (Snowy Hydro Limited website)
- Snowy Science - Snowy Flow Response Monitoring and Modelling program
- High-flow releases to the Snowy River during winter-spring 2016: Frequently asked questions (PDF, 44.99 KB)
- Snowy River Increased Flows: Safety Management Plan - 2016 winter-spring high-flow releases into the Snowy River below Jindabyne (PDF, 292.97 KB)
- Media release - Snowy River high-flows set to commence (PDF, 82.27 KB)
Rising river alerts
The 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.
2016-17 water year
Table 1 outlines the 2016-17 annual targets for the Snowy Montane Rivers.
|Snowy Montane River Increased Flows||Release location||SWIOID Annual Target (GL)||Adjusted Implementation Annual Target (GL)||2016-17 Annual Volume (GL)|
|Murrumbidgee River @ Tantangara||Tantangara Dam||27||27||9.83|
|Goodradigbee River*||Goodradigbee Weir||12||12||7*|
Middle Creek Weir|
Strzelecki Creek Weir
|Snowy River - Island Bend||
Diggers Creek Weir
|Snowy River - Perisher Range#||Falls Creek Weir||30||-||-|
# Note: The management options for the Perisher Range still requires further analysis in order to be implemented. * A 12 month trial is being implemented in these locations during the 2016-17 water year.
There are two approaches being employed in the Snowy Montane River: (i) Snowy Weirs and (ii) Tantangara Dam.
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.
In the Murrumbidgee River below Tanatangara, 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 operation constraints at Tantangara Dam than compared to Jindabyne Dame.
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.
The details of these releases are located in the annual SMRIFs strategy.
- Strategy for the Snowy Montane Rivers Increased Flows
- Current Water Year – Murrumbidgee River Daily Releases (Snowy Hydro Limited website)
- Snowy Science - Snowy Flow Response Monitoring and Modelling program
Long-term water planning and management
DPI Water is developing a long term environmental water release strategy for the Snowy River and the Snowy Montane Rivers. This includes:
- developing a hierarchical set of environmental water objectives
- developing new principles to river rehabilitation using environmental water
- identifying recovery pathways
- identifying hydro-ecological relationships and flow thresholds
- identifying constraints to recovery
- defining recovery end points
- defining complimentary management actions
- defining the cultural water requirements in partnership with the aboriginal community.
Annual water allocations to the licences recovered from water savings and purchases in the western rivers determine the total volume of water available for the Snowy, Snowy Montane and Murray River Increased Flows programs each year.
The amount of water available influences the release strategy for the following year. Environmental flows to the Snowy River are then set in February for a 12 month period and implemented from May to April.
The NSW Government considers advice on the appropriate release strategy from a number of sources including the Snowy Water Technical Advisory Group. The release strategy for the Snowy River and the Snowy Montane Rivers for the following year is included in Snowy Hydro Limited's annual water operations.
On this page
- Water recovery targets
- Snowy water savings summary
- Snowy River Increased Flows
- Snowy Montane Rivers Increased Flows
- Water planning
- Lake Jindabyne reduction
- Snowy Flow Response Monitoring and Modelling program
- Snowy flows real-time data
- Snowy Water Licence
- Snowy Hydro water releases