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Blue Rock Lake


History

The reservoir’s construction began in 1979 and was complete in 1984. It has a capacity of 208,000 megalitres (ML).

Following construction of the dam, the safe yield of the Latrobe River system upstream of the Morwell River Junction was increased to 325,000 megalitres per annum.
The embankment of the dam is constructed from earth and rock fill material.


Purpose

With its rich reserves of brown coal, the Latrobe Valley generates 85% of Victoria’s electrical power and continues to be a vital base for the State’s economic growth. To meet the planned industrial expansion in the region, an assured supply of water is essential to meet industrial, private irrigation and domestic water requirements.

The Latrobe Valley electricity generating companies are able to extract 150,000 megalitres per annum of yield from Blue Rock, for use as cooling water in existing power stations and for future power generation expansion.

Gippsland Water, which is the urban water corporation for the Latrobe Valley, is able to draw 14,000 megalitres annually from Blue Rock to supplement Moondarra Reservoir.

Gippsland Water also pumps water from the Tanjil River to the township of Moe.

Water drawn from the storage is available to maintain minimum flows in the Latrobe River during periods of naturally low flows as required by the State Environment Protection Policy.


More than 100%

Why Does a Storage Sometimes Show As More Than 100% Full?

Sometimes our storages show as a little bit more than 100% full.
This happens when the reservoir is already 100% full, and water flows into the reservoir faster than it is being released. The dam cannot permanently retain this additional water as it is above the spilling point, but temporarily ponds it until water flowing in slows to a point where releases are higher, and the reservoir returns to a normal level.

During this period, the storage shows as slightly more than 100% full.

All of our dams have been designed to cope with this temporary ponding.


Statistics
RESERVOIR
Capacity 208,190 ML
Dead storage 1,000 MLL
Surface area 873 ha
Full supply level 140m AHD
Catchment area 360 km2
EMBANKMENT
Maximum height 72 m
Length (Excluding Spillway) 72 m
SPILLWAY
Crest length 41.5 m
Discharge capacity 100,000 ML per day

Power Generation

In 1992 Pacific Energy installed a small hydroelectric generator at Blue Rock Lake that gives a total capacity of 2.4 megawatts of power into the state network.

For more information please visit Pacific Energy.


Location


The Blue Rock Dam and Lake are located on the Tanjil River in West Gippsland – VicRoads Reference Map 97 E3


Bulk Entitlements

A Bulk Entitlement Order is a set of operating rules for a reservoir.

At Southern Rural Water (SRW) we deal with the following Bulk Entitlement Orders:

• Latrobe
• Maribyrnong
• Yallourn Energy
• Werribee
• Thomson/Macalister

Because more than one organisation or group can have shares (or entitlement) in the water being held in a reservoir, each shareholder must follow rules about:

• the volumes that can be taken from the reservoir, system or waterway
• costs of managing the system, and how they are shared

At a number of reservoirs, SRW acts as the storage manager on behalf of all shareholders.
As a storage manager, we: 

allocate water (both increases and decreases) according to the inflow and capacity shares held by shareholders
ensure that we meet the rules for passing flows downstream for environmental purposes
• release water to meet a shareholder’s request

Passing flows are a vital part of our Bulk Entitlement Orders and are met before allocation requests are supplied.

Environmental Entitlements

Environmental Entitlement Orders spell out a whole pattern of environmental flows that are required downstream of a reservoir – from how long they last, to how frequently they flow and how large they are.

Environmental flows are designed to mimic the natural conditions of rivers. It is not just about the amount of water but also the timing and quality. In each order, environmental flow requirements are low during the summer and autumn, and are much higher during winter and spring.

Environmental flows are vital to supporting the river’s ecological processes. High flows provide triggers for fish breeding and supply water for fish passage, so that they are able to move up and down rivers to appropriate habitat. They also keep estuaries open and provide recreational opportunities. Low flows in summer maintain fish refuges and connect habitats. Spring floods regenerate wetlands and floodplains and replenish the river channel.

Monitoring

To make sure that we comply with the rules about passing environmental flows, we:

• perform random checks at points along rivers, to ensure that customers are taking only the amount of waterthey have ordered
• maintain a number of gauging stations with alarms that alert us of unusual changes in water levels.

More information
For more information contact us on 1300 139 510 or visit www.srw.com.au.

Download Factsheet


SRW's role during floods in the Latrobe System - Blue Rock

Water storages in the area are not designed so that Southern Rural Water can actively manage floods
Southern Rural Water helps to provide river flow information during floods
Please keep clear of dams and spillways during floods

The Latrobe System has two storages managed by Southern Rural Water:

• Blue Rock Lake, which has a capacity 208,188 megalitres (ML)
• Lake Narracan, which has a capacity of 7,230 ML

Their purpose is to store water for various uses – power generation, industrial, urban and irrigation purposes, as well as storing water for the environment.

When the storages were designed, they were not intended to allow Southern Rural Water to significantly influence releases in times of flood.

Blue Rock Lake has an ungated spillway, and the valves available to release water from the storage are very small compared to the flows into the dam during heavy rain. The spillway is set at a fixed level and once the storage fills to this level, water begins to flow over the spillway.

Lake Narracan stores a very small volume of water compared to its large catchment. Even if it was empty at the start of a flood, it would quickly fill up and releases from the dam would need to match the flows into it. Southern Rural Water must operate Lake Narracan in times of flood to ensure that it remains in a safe condition.

Blue Rock Lake operations during floods

During floods, Southern Rural Water inspects the dam regularly to ensure it remains in good condition, and also monitorsflows into and out of the dam.

We provide advice to the Bureau of Meteorology and the SES if flows out of the dam are likely to exceed the flood warningtriggers at Tanjil South, downstream of the dam.

Despite the fact that we have little ability to control releases from the storage, the peak rate of flow from the dam is significantly less than the peak rate of inflow during floods.

This is because the spillway of the dam is relatively small, and limits the amount of water released during floods. The large surface area of the lake allows excess water to safely pool behind the dam embankment (also known as surcharging) while it waits to be released through the spillway.

As an example, in 2011 the lake was full at the start of a flood. Flows into the lake peaked at about 6,000 ML/d. The flow out of the dam peaked at about 2,850 ML/d, or about half of the inflow.

This means that, compared to when there was no dam at the site, the severity of flooding downstream is significantly reduced.

In this case, the ability to reduce the severity of downstream flooding was built into the dam design, rather than any Southern Rural Water action during floods.

Operating Lake Narracan during floods

Lake Narracan has a gated spillway with four flood gates designed to pass water underneath, allowing us to maintain the storage at a specific operating level.

Despite the presence of the spillway gates, the amounts released are governed almost entirely by the flows into the storage. This is because Lake Narracan’s storage volume is tiny in comparison to its catchment size.

During floods, Southern Rural Water regularly inspects the condition of the dam to ensure it remains safe and fit for purpose. Rainfall and river flows into the dam are carefully monitored so we can make decisions about releases from the dam.

We provide advice to the Bureau of Meteorology and the SES if outflows are likely to exceed the flood warning triggers at Thom’s Bridge and Rosedale, downstream of the dam.

As a comparison, the storage at Lake Narracan is less than 1% of that held by Thomson Dam but its catchment is about four times larger.

Any spare storage capacity will be filled within hours, and so releases from the dam in times of flood need to closelymatch the flows into it.

Flow information

When we know high rainfall is possible, our staff work closely with other agencies such as the SES, local councils and the Bureau of Meteorology to provide information on the flows passing through our dams during floods.

Southern Rural Water provides daily updates on its website (www.srw.com.au) about thewater levels in local storages and also has a web page which has links to Bureau rainfall forecasts, flood warnings, river levels and emergency assistance provided by the SES. During floods above particular trigger levels, we provide regular updates on flows out of the dams on our website, Twitter and Facebook pages.

Keep clear of our dams

During high river flows we urge all visitors to stay well away from our dams, especially the spillways or other release points, and the downstream water course.

Please:

• follow any requests from Southern Rural Water staff
• take note of signage and fencing, and
• stay away from any prohibited areas, particularly the dam walls and spillways.

Playing on or near a spillway during a flood is a recipe for disaster.

We strongly recommend that if you are in a flood prone area that you and your family familiarise yourself with the SES’s Flood Safe information on their website – www.ses.vic.gov.au/get-ready/floodsafe

More information
For more information contact us on 1300 139 510 or visit www.srw.com.au

Download Factsheet

Statistics
RESERVOIR
Capacity 208,190 ML
Dead storage 1,000 MLL
Surface area 873 ha
Full supply level 140m AHD
Catchment area 360 km2
EMBANKMENT
Maximum height 72 m
Length (Excluding Spillway) 72 m
SPILLWAY
Crest length 41.5 m
Discharge capacity 100,000 ML per day
Blue Rock Lake recreational fishing haven

The Victorian Government is introducing new measures to help make Blue Rock Lake one of Victoria’s premier Australian Bass fisheries.

Recreational anglers will now have better access to the Lake, near Moe, thanks to new boating rules.

New boating rules at Blue Rock

New boating rules now apply at Blue Rock Lake.

The new rules are the first real change since Blue Rock Lake was built in the early 1980s. The old rules were designed to restrict erosion when the lake was first built. Erosion is no longer a problem, but the rules prevented modern recreational fishing vessels from using the lake.

As part of the Victorian Labor Government’s ‘Target One Million’ plan to get one million people into recreational fishing, new rules have been developed over the past two years to balance the desire for increased access, modern fishing boats, local community wishes and legal requirements.

These rules are set by Transport Safety Victoria (TSV).

What are the details?

The new rules remove limits on boat length and engine power, and lift maximum speed from 5 knots to 15 knots in designated zones.

Two “no boating areas” have been retained for swimmers, and a large area has been restricted to five knots only which will be suitable for kayakers. These areas will be clearly marked.

These changes are in line with the Marine Safety Act and will allow more boat owners – particularly those with boats with larger motors – to access Blue Rock Lake. However the speed restriction of 15 knots will address water quality and safety issues for more passive users such as kayakers and swimmers.

The 15 knot limit is below the speed commonly used for most water skiing and jet ski activities and these activities will continue to be deterred via this speed limit.

Blue Rock Lake boating restrictions table

Maximum boat length Old rules 4.3m
Maximum boat length New rules No limit

Maximum output Old rules10Hp (7.5Kw)
Maximum output New rules No limit

Maximum speed Old rules 5 knots
Maximum speed New rules 15 knots, except in designated safety zones (5 knots)

No go zones Old rules No boating in areas around SRW infrastructure and designated swimming zones
No go Zones New rules No boating in areas around SRW infrastructure and designated swimming zones

How is Southern Rural Water going to manage increased usage?

Southern Rural Water has extensive experience in managing compliance with boating and recreational rules at its major dams across the state. This compliance work has had extremely positive feedback from most users and the local community.

During this trial period at Blue Rock Lake, we will:

• conduct random land and on-water compliance activities
• provide educational signage and flyers to users of the lake
• check regularly with lake users for feedback
• check regularly with the local community for feedback.

We also welcome your views via our Customer Service Centre on 1300 139 510, via email to srw@srw.com.au or via our Facebook and Twitter accounts.

At the end of the trial period in September 2016, Southern Rural Water will consider all feedback and compliance experience, and draft a report and submit to Transport Safety Victoria with our recommendations.

More information For more information, or to discuss any concerns abouyt the changes, please contact our office on 1300 139 510.

Download Factsheet

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