Managing water storages

Managing Water Storages

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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 

(Update: 10:00 AM, Wednesday 20 June 2018)

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. The storages are currently releasing between:
 
Laanecoorie Reservoir: 40 - 130 ML/d
Cairn Curran Reservoir: 30 - 130 ML/d
Tullaroop Reservoir: 20 - 40 ML/d
 

Lake Buffalo is operating at sill level and passing all inflows.

Releases are meeting normal operating requirements and are around 20 ML/d. 
 
Releases are meeting normal operating requirements and are around 100 ML/d.
 
 

A delivery of environmental flows is planned to commence from Goulburn Weir on Wednesday 20 June 2018. Depending on catchment inflows at the time, a portion of this delivery will be required as release from Lake Eildon. For more information, please see the fact sheet under the Goulburn Weir expander below.

The release yesterday, today and a forecast for the next 7 days are outlined below:

Last Upated: 10:00 AM, 20 June 2018

Releases from Lake Eildon

Date

Month

Release (ML/day)

Yesterday 19 June 2018 1,500
Today 20 June 2018 400
Forecast 21 June 2018 3,000*
Forecast 22 June 2018 5,000*
Forecast 23 June 2018 7,000*
Forecast 24 June 2018 7,500*
Forecast 25 June 2018 8,000*
Forecast 26 June 2018 8,000*
Forecast 27 June 2018 8,000*

*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.

A delivery of environmental flows is planned to commence from Goulburn Weir on Wednesday 20 June 2018. Releases will gradually increase daily to be about 9,500 ML/d by Thursday 28 June. The flows will then reduce daily to be between 500 ML/d and 940 ML/d by 24 July at Murchison and 28 July at McCoy Bridge. The dates and peak flow rates for this event may vary depending on climatic conditions. More information is available in our Goulburn River environmental flows fact sheet.

Environmental flows are a normal feature of Goulburn River operations and regularly occur. River levels of these planned releases will be well below the minor flood level. For planning of environmental releases in the Goulburn River visit the Goulburn Broken Catchment Management Authority at http://www.gbcma.vic.gov.au/. 

The release yesterday, today and estimated forecast for the next 10 days are outlined below:

Last Updated: 10:00 AM, 20 June 2018 

Releases from Goulburn Weir

Date

Month

Release (ML/day)

Yesterday 18 June 2018 830
Today 19 June 2018 940*
Forecast 20 June 2018 1,186*
Forecast 21 June 2018 2,000*
Forecast 22 June 2018 4,000*
Forecast 23 June 2018 6,200*
Forecast 24 June 2018 8,000*
Forecast 25 June 2018 9,000*
Forecast 26 June 2018 9,300*
Forecast 27 June 2018 9,500*
Forecast 28 June 2018 9,500*
Forecast 29 June 2018 9,300*

*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.

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.

Last updated: 24 August 2015

 

Inter-Valley Trade transfers

(Last updated: 12 June 2018)

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

Delivery of water from the inter-valley trade account from the Broken system to the Goulburn system has now concluded with the balance now fully delivered for season 2017/18.

Delivery of water from the inter-valley trade account from the Goulburn and Campaspe systems to the Murray system has now concluded for season 2017/18.

The timing of transfers of from the inter-valley trade accounts 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 in the inter-valley transfer accounts in each system, please refer to the Victorian Water Register website.

Below is a table containing the volumes delivered in gigalitres each month from the Goulburn inter-valley trade account to the Murray system over the last 5 water years.  

Season Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun       Total
2012/13 0 0 0 0 0 53.5 46.2 0 0 0 0 0 99.7
2013/14 0 0 0 12.5 14.2 2.9 35.1 61.1 17.0 0 0 0 142.8
2014/15 0 0 0 21 67.4 21.7 42.9 36.4 47.4 3.7 0 0 240.6
2015/16 0 0 0 0 10.8 10.7 13.7 15.4 21.1 0 0 0 71.7
2016/17 0 0 0 0 0 0 38.2 29.8 20.5 21.2 0 0 109.7

 

Below is a table containing the volumes delivered in megalitres each month from the Campaspe inter-valley trade account over the last 5 water years.  

Season Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun       Total
2012/13 0 0 0 0 0 0 0 0 0 0 0 0 0
2013/14 0 0 0 0 7,345 246 0 4,806 5,516 0 0 0 17,913
2014/15 0 0 0 0 14,596 2,510 1,486 1,533 168 0 0 0 20,290
2015/16 0 0 0 0 934 928 740 656 926 0 0 0 4,183
2016/17 0 0 0 0 0 0 0 0 0 0 0 0 0

 

Below is a table containing the volumes delivered in megalitres each month from the Loddon inter-valley trade account over the last 5 water years.  

Season Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun       Total
2012/13 0 0 0 0 0 0 0 0 0 0 0 0 0
2013/14 577 578 0 23 1,530 70 0 0 0 0 0 0 2778
2014/15 0 1,666 0 0 0 0 0 0 761 876 0 0 3,303
2015/16 0 0 0 0 0 0 0 0 1,717 2,937 0 0 4,654
2016/17 0 0 0 0 0 0 0 0 0 0 0 0 0

  

Below is a table containing the volumes delivered in megalitres each month from the Broken inter-valley trade account over the last 3 water years.  

Season Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun       Total
2014/15 0 0 0 0 653 590 913 1,004 969 1,388 0 0 5,517
2015/16 0 0 0 0 0 0 0 0 0 0 0 0 0
2016/17 0 0 0 0 0 160 69 1279 1,494 1,111 506 0 4,619

 

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: 1 February 2018

  

  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 customer 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: 6 June 2018

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 2016/17

Ovens and King System Spill Notifications

Diverters on the Ovens and King systems have spill entitlements that can be accessed each water year from 1 July until the time when the supply storage ceases to spill or pass flows above in-valley requirements.

GMW monitors storage inflow conditions and forecast when regulated releases are expected to exceed inflows, i.e. when the storage ceases to spill. The end of access to spill entitlement is usually towards the end of the calendar year, but varies depending on seasonal conditions.

GMW aim to provide 2 to 3 weeks’ notification to customers that access to spill entitlements will end for the current water year.

For customers that have lodged an order through WaterLINE, their meters are read on the date when access to spill entitlements ends. Use up to their spill entitlement is deemed and any additional use is deemed against their high-reliability water shares (HRWS). All other customer use will be deemed against their HRWS entitlement at the end of the season. Customers who have not lodged an order through WaterLINE will have all use deemed against their HRWS.

All customers are encouraged to submit all orders through WaterLINE to ensure supply can be met and accurately accounted for.

King system

King River and regulated anabranch diverters are advised that Lake William Hovell will officially stop spilling on  21 December 2017. Letters have previously been sent to all customers providing formal notification that access to Spill Reliability Water Shares will cease on Thursday 14 December 2017. This has been extended to Thursday 21 December 2017 following an increase in storage inflows.

Ovens system

Buffalo River, Ovens River and regulated anabranch diverters are advised that Lake Buffalo will officially stop spilling on  13 February 2018. Letters will be sent to all customers providing formal notification that access to Spill Reliability Water Shares will cease on Tuesday 13 February 2018

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.

 

Useful Links 

 

 

Last Updated: 8:15 AM, 31 January 2018

Releases from Lake Eildon

Date

Month

Release (ML/day)

Yesterday30January 20184,000Today31January 20184,000Forecast1February 20184,000*Forecast2February 20184,000*Forecast3February 20184,000*