Managing water storages

River Levels
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Rainfall Forecast
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Water Status Reports
Water Status Reports
Emergency Assistance
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Operating and maintaining 16 water storages across northern Victoria that can cumulatively hold over 9,000,000 megalitres of water - or 70% of the total water storage capacity in Victoria - is an ongoing and major part of Goulburn-Murray Water's (GMW) business.

GMW closely monitors all storages, their inflow and downstream releases to ensure harvesting opportunities are maximised and stored water is managed efficiently for all our customers.

While the primary role of our water storages is to harvest and store customers' water entitlements, GMW can provide flood mitigation benefits at some storages where possible. Pre-releasing water from a GMW water storage can influence the rate at which a storage fills and is a valuable tool to balance entitlement reliability and flows downstream of a storage.

This webpage provides information on the status of current and forecast storage releases, information on inter-valley trade transfers and estimated storage volume projections for some storages. The links above provide more detaild data and information on river levels, storage releases and any flood warnings.

Storage Releases Summary 

(Updated 8:00 AM, Friday 9 December 2016)

This information covers the status of releases from the major storages managed by GMW. The forecast releases are an indication only and may change depending on weather conditions and customer requirements. Please check this information daily if your property is subject to inundation at high river levels.

Storage releases may change in response to inflows, weather forecasts and observed rainfall.  For real-time river levels please visit the Bureau of Meteorology River Levels website (see link above) or access GMW's Water Status Reports (see link above). 

Releases from the Loddon storages are meeting normal operating requirements and are currently releasing between:
Laanecoorie Reservoir: 70 - 100 ML/d
Cairn Curran Reservoir: 20 - 30 ML/d
Tullaroop Reservoir: 10 - 20 ML/d
 

Lake Buffalo is at capacity and passing all inflows.  

Releases from Lake Nillahcootie are currently meeting normal operating requirements.
 
Releases from Lake Eppalock are meeting normal operating requirements.
 

Releases from Lake Eildon are currently meeting normal operating requirements.

The release yesterday, today and a forecast for the next 3 days are outlined below:

Last Updated: 8:00 AM, 9 December 2016 

Releases from Lake Eildon

Date

Month

Release (ML/day)

Yesterday 8 December 2016 2,000
Today 9 December 2016 2,000
Forecast 10 December 2016 2,000*
Forecast 11 December 2016 2,000*
Forecast 12 December 2016 2,000*

*Actual releases from Lake Eildon may vary from those forecast at any time without notice.   

What do changes in river flows mean for river levels?

The table below provides a summary of the river levels at various flow rates as measured at the gauges on the Goulburn River at Eildon, Trawool and Seymour.

Please note that the table below is specific for the river gauges at Eildon, Trawool and Seymour and the relationship between flows and river level will vary along the river as the profile changes.

This information does not relate to absolute water depth in the river however the table provides an indication of what various flows mean for river levels. For example, if flows increased from 5,000 ML/day to 6,000 ML/day, the river level at Trawool would increase by around 0.2 m.

River flow (ML/day) River level at Eildon (m) River level at Trawool (m) River level at Seymour (m)
1,000 1.0 0.7 1.0
2,000 1.3 1.0 1.3
3,000 1.5 1.2 1.5
4,000 1.7 1.4 1.7
5,000 1.9 1.6 1.9
6,000 2.1 1.8 2.0
7,000 2.2 1.9 2.2
8,000 2.3 2.1 2.3
9,000 2.5 2.3 2.4
10,000 2.6 2.4 2.5

Please note: the table above provides an indication of the scale of typical river flows and flows may exceed 10,000 ML/day in response to rainfall in the catchment.

Further Information for Lake Eildon:

Tributary Flows:

There are a number of other tributaries that contribute to the river levels downstream of Lake Eildon such as the Acheron, Rubicon and Yea Rivers. Levels in these tributaries can be monitored on the Bureau of Meteorology website.

Releases from Goulburn Weir are currently meeting normal operating requirements.

The release yesterday, today and estimated forecast for the next 4 days are outlined below:

Last Updated: 8:00 AM, 9 December 2016 

Releases from Goulburn Weir

Date

Month

Release (ML/day)

Yesterday 8 December 2016 830
Today 9 December 2016 830
Forecast 10 December 2016 830*
Forecast 11 December 2016 830*
Forecast 12 December 2016 830*
Forecast 13 December 2016 830*

*Actual releases from Goulburn Weir may vary from those forecast at any time without notice.    

Flows in the Goulburn River may increase at any time due to rainfall in the river catchment. The 'River Levels: Provided by BoM' link under the heading of this page provides access to river height information for a number of sites along the Goulburn River. 

What do changes in river flows mean for river levels?

The table below provides a summary of the river levels at various flow rates as measured at the gauges on the Goulburn River at Murchison, Shepparton and McCoy Bridge.

Please note that the table below is specific for the river gauges at Murchison, Shepparton and McCoy Bridge and the relationship between flows and river level will vary along the river as the profile changes.

This information does not relate to absolute water depth in the river however the table provides an indication of what various flows mean for river levels. For example, if flows increased from 2,000 ML/day to 3,000 ML/day, the river level at Murchison would increase by around 0.5 m.

River flow (ML/day) River level at Murchison (m) River level at Shepparton (m) River level at McCoy Bridge (m)
1,000 0.9 2.8 1.5
2,000 1.5 3.1 2.1
3,000 2.0 3.4 2.6
4,000 2.4 3.7 3.1
5,000 2.8 4.1 3.5
6,000 3.1 4.4 4.0
7,000 3.5 4.8 4.4
8,000 3.8 5.1 4.8
9,000 4.1 5.5 5.2
10,000 4.5 5.9 5.5

Please note: the table above provides an indication of the scale of typical river flows and flows may exceed 10,000 ML/day in response to rainfall in the catchment.

Forecast Storage Volume Projections 

Climatic conditions, storage inflows and customer demands influence the volume of water held in storage throughout the year. Given the uncertainty surrounding each of these factors, exact information about future storage volumes cannot be provided or guaranteed.

Using the current storage volume, historical climate and inflow statistics, historic patterns of use and known commitments for releases in a season, storage projections under various climatic scenarios are possible.

It is important to note there are a number of underlying assumptions in the modelling used to develop the storage volume estimates and are subject to change at any time.

The storage projections are forecasts only; they are not a commitment by GMW to operate the storages to any particular scenario. The highly variable nature of climatic conditions, storage inflows and customer demands means the actual storage volume throughout the year will differ to the projections given here.

Storage volume estimates will be updated throughout the season.

Lake Eppalock

Last updated: 24 August 2015

 

Inter-Valley Trade transfers

(Last updated: 10 October 2016)

Transfer of inter-valley trade water is required to deliver water traded between different systems.

As at the date of this update, there has been no transfer of inter-valley trade water from the Goulburn, Campaspe, Loddon or Broken systems in season 2016/17. Transfers from the Goulburn to the Murray system are likely to commence in January 2017, with the potential for a total transfer volume of 160 GL to occur from January 2017 to the end of season 2016/17.

The timing of transfers of inter-valley trade water is highly dependent on catchment conditions and system demands. Plans for transfers of water are subject to change at any time.

To view the details of the volumes of inter-valley transfer water in each system, please refer to the Victorian Water Register website.

Forecast Storage Volume Projections

Climatic conditions, storage inflows and customer demands influence the volume of water held in storage throughout the year. Given the uncertainty surrounding each of these factors, exact information about future storage volumes cannot be provided or guaranteed.

Using the current storage volume, historical climate and inflow statistics, historic patterns of use and known commitments for releases in a season, storage projections under various climatic scenarios are possible.

It is important to note there are a number of underlying assumptions in the modelling used to develop the storage volume estimates and are subject to change at any time.

The storage projections are forecasts only; they are not a commitment by GMW to operate the storages to any particular scenario. The highly variable nature of climatic conditions, storage inflows and customer demands means the actual storage volume throughout the year will differ to the projections given here.

Storage volume estimates will be updated throughout the season.

Lake Eppalock

Last updated: 29 November 2016

        

Key notes:

  • Probability of exceedance (PoE) inflow percentages represents the inflow volumes that have a particular chance of being exceeded. For example the 90% PoE inflow scenario considers the storage inflow volume that has 90 chances in 100 of being exceeded - i.e. dry conditions.
  • Assumptions about custmer demand and losses such as evaporation have been used according to the inflow scenario i.e. drier conditions assumes higher evaporation loses.  

Lake Eildon

Last updated: 1 December 2016

        

Key notes:

  • Probability of exceedance (PoE) inflow percentages represents the inflow volumes that have a particular chance of being exceeded. For example the 90% PoE inflow scenario considers the storage inflow volume that has 90 chances in 100 of being exceeded - i.e. dry conditions.
  • Demand is the average customer demand in the 10 years up to 2015/16

Dams - How they work

Ever wondered how a dam works? How is the water released and where does it go?

Our 3D animation is designed to show you what a dam looks like, the infrastructure, and challenges in managing water. It allows you to explore different parts of the dam with a slider that demonstrates the effect of changes in water levels.

Frequently Asked Questions

Yes.  GMW operates dams with two different types of spillways, fixed crest spillways or gated spillways.
 
Fixed crest spillway dams generally have relatively small outlet works and operate on a ‘fill and spill’ basis. As inflows enter the dam, the water level in the dam increases until it reaches the spillway crest level where it will overflow into the downstream river channel. The fixed crest level is at the Full Supply Level (FSL) of the dam and is the point at which the dam is 100% of capacity. The embankment of the dam is designed to allow the water level to naturally surcharge above 100% of capacity and allow the spillway structure to ‘throttle’ outflow. Dams of this type provide some flood mitigation by attenuating the flood peak. There is no operational control from the dam operator in passing floods through these types of dams.
 
Gated spillway dams are configured with large gates in the spillway that enable water to be stored above the spillway crest level. As the dam’s FSL is above the spillway crest level, the gates must be closed to allow the dam to fill to 100% of capacity. During winter and spring, water is harvested in the dam by following a target filling curve that balances resource increases against a degree of flood mitigation. Flood water is passed through the spillway by opening the spillway gates. The embankments on GMW’s gated spillway dams are not designed to be surcharged in the same way fixed crest spillway dams operate. The flood operating procedures for gated spillways aim to pass inflows through the dam while maintaining the level within the dam at or below FSL. Generally the operation of gated spillway dams involves using pre-releases as any air space (the available volume between the lake level at the beginning of an event and FSL) to delay the onset of flooding and reduce the flood peak. The amount of flood mitigation that can be provided depends on the amount of air space available and the size of the flood. Only 3 of GMW’s 16 dams have gated spillways – Eildon, Buffalo and Cairn Curran.
A pre-release can manage the rate of a storage filling and be a valuable management tool to balance GMW customer’s water entitlement (that is stored in water storages) and downstream flood impacts. It’s a little like letting the plug out of a bath for a moment when it is nearly full.

GMW Pre-release from Dams Policy [80 KB]

Pre-releasing from Eildon is normal operating procedure for the dam and has been done in the past where the dam has been near full during winter and spring. Pre-releases are also made from our other gated spillway dams, Buffalo and Cairn Curran. Due to the design of the spillway, there is limited opportunity to pre-release from our other dams. Where possible GMW tries to maintain some  "airspace"  in all the dams during winter and spring.
The pre-release of water from any storage will not minimise the effects on downstream users, it provides a balance between resource harvesting and flood mitigation.  If we receive a large inflow to the water storage, there is still the risk of flood downstream.
 
Unfortunately it’s not that simple.  Water in a storage is owned by customers and a storage simply holds it for them until they are ready to use it. The level in the water storage during winter and spring is managed in accordance with rules and procedures that GMW must adhere to. The rules limit the opportunity for GMW to pre-release significant volumes of water for flood mitigation.  There are also potential downstream impacts that have to be considered and communicated. 

The impact of rain in a catchment is not an exact science – a small amount of rainfall can result in a large inflows and vice-versa. Significant drawdown of storage levels can only be made prior to a rainfall event once an accurate rainfall forecast is available which is generally 3-4 days in advance. This limits the volume of water which can be drawn down at short notice.
The primary role of a water storage is to harvest and store customers' water entitlements, GMW operates the dams to provide flood mitigation benefits where possible.  Generally large water storages are not designed or operated specifically for flood mitigation

The amount of flood mitigation a water storage can provide depends on a number of factors - including the operating rules of the storage, the size of the flood event, the level of water in the dam at the beginning of the event and the release capacity of the spillway.

Water storages may provide significant mitigation for small floods and may significantly reduce downstream flooding. The amount of mitigation generally reduces as the size of the flood increases, so there may be little mitigation benefit for large floods.
 

There are four ways water can be released from Eildon.

Most releases from Eildon are made through the hydro power station operated by AGL. Water is taken in through the base of the outlet tower and passed through a large conduit under the embankment to the power station. Releases up to about 20,000 ML/d are made this way. You won’t see much evidence of the releases other than some turbulent flows downstream of the dam.

The other ways water is released is through a large ‘low level’ valve adjacent to the hydro station, large ‘irrigation’ valves in the spillway or through the spillway flood gates. Generally the low level and irrigation valves are only operated as a back-up when releases can not be made through the hydro station. Releases will only be made through the spillway gates during flood events when the volume of outflow exceeds the release capacity of the hydro station.

eildon spillway

 

The Eildon spillway is designed to pass excess flood water from the storage.
The Eildon spillway is only used during flood events when the volume of outflow exceeds the release capacity of the hydro station.
A spillway is a feature of a dam which is designed to pass excess flood water from the storage. Spillways are generally large concrete structures constructed beside or within the embankment. When the dams are full and inflows enter the dam the excess water is released either through the operational outlet works (for normal small flows) or over the spillway for larger flood flows.

 

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