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EUROBODALLA WATER SUPPLY

GENERAL INFORMATION

Deep Creek Dam pumping station

Prepared by Eurobodalla Shire Water and Waste Department – Eurowater - August 2007

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The following information is extracted from

HEADWORKS OPERATION & MAINTENANCE MANUAL

VOLUME 1 – TEXT REVISION 01 SEPTEMBER 2006

Prepared by Eurobodalla Shire Water and Waste Department – Eurowater - August 2007

GENERAL

Water is a relatively scarce resource, and it is very costly to provide. Consequently, the use

and quantity of water provided must be managed to ensure that the water resource is used as

efficiently as possible.

In other parts of the country there are competing uses for water. Dams are used to store water,

however they must release a certain amount of water downstream for ‘riparian’ releases, (ie

when a dam is built, water is not allowed to be cut off to existing downstream users). There is

also competition for the stored water for domestic supply and agriculture (irrigation). In

addition, some dams are purposely never filled to capacity in order to provide a buffer form

flood mitigation, (ie reduce the magnitude of the flood), and this ‘air space’ competes with

both agriculture and domestic supply for a share of the dam’s volume.

In Eurobodalla Shire there is no widespread irrigation, consequently there are little or no

water use conflicts. River extraction limits will apply in the foreseeable future. For details the

IWCMP should be consulted. The full version can be found at

www.esc.nsw.gov.au/IWCMP/IWCMP.html

In managing the use of water, consideration must be given to both the management of the

water distribution system, and the management of the water demand on that system.

WATER SYSTEM DESCRIPTION

General

Prior to 1983 Eurobodalla Shire was served by two separate schemes. Then the system was

augmented, linking the two schemes namely the Batemans Bay/ Moruya Scheme in the north

and the Narooma/ Tuross Scheme to the south. This augmentation has enabled the supply of

water from the Deep Creek Dam storage through the entire shire during droughts or floods

when the river supplies are not available due to either lack of water or high turbidity.

However both schemes can still operate independently in times of normal river flow. The cut-

off point of the schemes can be changed to suit river conditions.

The flexibility of the system is such that Central Tilba could be supplied from Deep Creek

Dam and Maloneys Beach could be supplied from the Tuross River if the need arises.

The village of Tilba Tilba has a private supply whilst Bega Valley Shire Council is

responsible for the supply to the settlements of Wallaga Lake and Akolele.

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The system is supported by three raw source pump stations at each of the River inlets which

pump water straight into the water supply system and the local reservoirs. Booster pump

stations are also installed to pump water between reservoirs when insufficient pressure flows

are evident.

Water Sources

The Shire’s water supply can be drawn from three types of sources being the surface water

sources at Buckenboura River, Moruya (Deua) River and Tuross River; underground spring

water from Mount Dromedary; and boreholes located at Broulee and Tuross.

Surface Water Sources

Water must be lifted from the rivers and pumped into reservoirs. In order to do this, pumping

stations have been constructed on the riverbanks at Buckenboura, Moruya and Tuross Rivers.

The pumping stations are by necessity located inland so as to be above the tidal limit and

ensure only fresh water is extracted

The Moruya River is the

major source of water for

the Shire’s Water Supply

Scheme and filling of

Deep Creek Dam with a

catchment of 38,000

hectare.

The Buckenboura River is

a tributary of the River

Clyde and has a

catchment area of 21,000

ha. A weir constructed

across the Buckenboura

River allows water to be

stored and is mainly used

to put water into Deep

Creek Dam.

The Tuross River is the

principal source of water

for the southern scheme

with a catchment area of

53,100 ha.

All three rivers contribute

to a total maximum

annual yield of 5880 ML

(2003), assuming no

limitations on supply.

Buckenboura Weir During the drought of

2004 the yield was

reduced to 3543 ML.

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Underground Sources

1. Springs

Mount Dromedary had a weir constructed in 1938 in the upper reaches of Dromedary Creek.

This was the original public water supply in the Eurobodalla Shire servicing Central Tilba

and Narooma. Catchment above the weir is 200 ha however flows are supplemented

substantially by underground springs and since there are no measurements or gauging of the

supply made, yields cannot be accurately determined. This source is now redundant as water

is supplied from the Tuross, Moruya rivers or Deep Creek Dam.

2. Boreholes

During the droughts of the early 1980’s and subsequent years, the surface water sources

almost dried up, and additional water was obtained from four bores sunk south of Broulee

and north of the Moruya River in the area which is now George Bass Drive.

Reasonable yields were obtained and the bores were converted to production wells. The water

drawn from the bores was pumped into the old Batemans Bay – Moruya trunk main. This

supplemented the supply from Moruya River to Batemans Bay. A small chlorine dosing

station was constructed to treat the bore water before entering the water supply system.

All Broulee bores were later capped and pump sets and sheds removed, however in

2004/2005 one bore (Bore No.2) was reinstated due to droughts in 2002/2003 for the supply

of non-potable water for road construction work. Filtration would be required to make this

source potable.

Due to the lack of surface water during the last extended drought period, 5 bores were sunk

adjacent to the Tuross River, upstream of the existing River Pump Station, between October

and December 2004.

These bores are now

fully operational and

are earmarked for

emergency drought

supply.

The outstanding issue

still to be addressed is

the high iron and

manganese content

which will have to be

removed by filtration

if the water was used

for prolonged periods.

Drilling rig at one of the Tuross River bore sites

Iron and manganese in the quantities present does not directly affect health and is more of an

aesthetic parameter as a build up can cause dirty water.

Water treatment methods are currently being investigated.

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Deep Creek Dam

Deep Creek Dam was commissioned in 1983 as an off stream storage dam located on Deep

Creek. Like the Buckenboura River, Deep Creek also flows into the Clyde River. Dam

storage capacity at full supply level is 4,900ML. A catchment area of 320 ha does not

contribute any sizeable runoff and filling of the dam is achieved through pumping water from

the Buckenboura and Moruya Rivers. The relatively small catchment of Deep Creek Dam

assists to keep the water quality clear during heavy rain events by limiting large run-off

which increases water turbidity.

The purpose of Deep Creek Dam is to provide the water supply system with a security of

supply. Water is only pumped from the dam:

during droughts, when the river intakes cannot provide sufficient water;

during periods of high demand (summer holidays) if the river intakes cannot provide

enough water;

during flood periods, when the river water is dirty and not suitable for distribution.

Deep Creek Dam

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Reservoirs

Reservoirs are large circular tanks constructed of concrete or steel. The main distribution

reservoir supply other reservoirs from which the water is supplied directly into reticulation to

the consumer.

The purpose of reservoirs is twofold:

to maintain storage for peak demand period;

to maintain capacity for fire fighting demands.

Tuross Head Reservoir

Water is supplied to consumers via reservoirs rather than directly from pumping stations

because:

the peak demand on a water system is usually of an evening, and the demand on the

system can be of the order of 1.5 to 2 times the average demand. By using reservoirs to

even out this demand, the pumps need only pump the average daily flow, rather than the

peak demand flow which is much higher. This allows smaller pumps and pipes to be used

and saves on energy costs;

if a pump breaks down, consumers will still be supplied with water from the reservoir.

Reservoirs are located on hills so that the water has sufficient pressure to flow by gravity to

all areas connected into the reticulation system. Due to the undulating nature in the

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Eurobodalla Shire area, available pressure to the consumer does vary within the same supply

area. The higher the location of the dwelling relative to the reservoir, the less pressure will be

available. Height in relation to rather than distance from the reservoir is the main factor.

Within Eurobodalla there are 35 reservoirs, of varying sizes ranging from 100,000 litres to

15,000,000 litres with a total holding capacity of 113,000,000 litres

Pipelines

1. Trunk mains

All pipelines used to transfer water from pumping stations to reservoirs and between

reservoirs are classified as trunk mains. Trunk mains from reservoir to reservoir are also

termed gravity mains while those between reservoirs and pumping stations are also termed

rising mains. Properties are not usually allowed to connect directly into these pipes because

pressures can be much higher than allowable for houses and the chlorine content is generally

higher than permissible for consumption. This will ensure the chlorine residual is within

limits for consumption after the extended journey through the trunk main system. Some areas

of the Shire can be fed directly from trunk mains as back up in case the reservoir is not

available. A special ‘Pressure Reducing Valve’ is installed on these connections which

lowers the water pressure to prevent excessive pressure in the reticulation system.

The trunk mains within the Shire range in size from 250mm diameter to 900mm diameter.

Typical urban water reticulation layout.

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2. Reticulation mains

All pipelines from the supply reservoir to the consumer are classified as reticulation mains.

These are the mains that are used to connect the water meters to and provide the hydrants for

fire fighting purposes. Where possible the available pressure to the consumer is between 200

to 900kPa.

The reticulation mains within the Shire range from as small as 32mm to 450mm.

Telemetry System

The Water & Sewer Supply Telemetry System employs radio signals, phone lines and the

internet to monitor, control, record and transmit changes of state of Pumping Stations,

Reservoirs and Motorised Valves back to the main server in Council’s main office in

Moruya, known as the Central Monitoring Facility (CMF).

The CMF monitors and accesses the five main server sites at Narooma, Tuross, Batemans

Bay, Moruya and Tomakin.

Basic Telemetry layout for the northern part of Eurobodalla Shire

The telemetry system monitors and controls the following:

reservoir and dam water levels including chlorine residuals and turbidity of the water;

pump status of pumping stations including running times, current draw, faults etc;

bulk flow meter information on rates of flow and volumes;

battery back-up status of servers;

history of events for example alarm times and reasons for alarm, manual changes made to

the system from each server;

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motorised valves open and closing when demand requires it.

rain gauge readings where available.

Manual changes can be made to the system from remote computers for example to start or

stop pumps or enable the manual over-ride of valves to allow water flow into reservoirs from

Deep Creek Dam or other reservoirs.

WATER QUALITY MANAGEMENT

General

Water supplied in Eurobodalla Shire receives no treatment, other than chlorination. This is

because of the high quality of the river waters, which is primarily due to geography. As the

rivers are relatively short, with steep catchments, much of the catchment remains forested and

undeveloped for urban or agricultural use, hence there are very little pollutants in the water.

Treatment plants are under consideration because of the increased water quality standards –

refer to IWCMP. This notwithstanding, the water supplied is regularly tested for heavy

metals, pesticides, fertilisers, etc.

The major factors affecting water quality in the Shire are bacteria, turbidity, colour and algae,

and each of these is discussed below.

Bacteria

Bacteria are present in natural waters, predominantly due to animal excreta, dead animals,

etc. Consequently the bacteria need to be killed before supplying water to consumers. This is

achieved by putting chlorine in the water which kills the bacteria, and also provide a chlorine

residual, ie some free chlorine remains in the water throughout the distribution system to

prevent bacteria re-growing through the pipes. Chlorine is added to the water at Deep Creek

Dam, Moruya River intake, Tuross River intake and additional dosing is carried out at

reservoirs when required.

Points within the reticulation system are regularly tested to ensure that there is sufficient

chlorine remaining in the system, and the water is checked for bacteria.

Turbidity

Turbidity is the term given to refer to dirty or cloudy water. It usually consists of clay

particles suspended in the water; and these particles can shelter bacteria from chlorine.

Therefore, the turbidity should be below certain guideline values to ensure that the water

supply is adequately disinfected by chlorine. Buckenboura, Moruya and Tuross pumping

stations have permanent turbidity measuring devices in place which are monitored by

Council’s Radio Telemetry System.

During periods of flood, river flows are usually quite turbid, hence the water is not suitable

for supply. During these times water is supplied to the entire Shire from Deep Creek Dam.

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Turbidity in Tuross River during high flows

Colour

The term colour refers to the natural colour of the water, rather than the colour given by

suspended clay (turbidity). Colour primarily consists of organic acids and the water often

looks a tea-tree brown.

Colour in water does not directly affect health, and is more of an aesthetic parameter, ie

highly coloured water does not look appealing to drink even though it will not taste any

different and will not have any ill effects. Colour, however, does consume chlorine, therefore

more chlorine needs to be added to highly coloured water to achieve adequate disinfection.

Other than at Deep Creek Dam, colour is not directly measured at the water source, however

it is taken into account by measuring the amount of chlorine required to kill bacteria and

provide a residual with the use of a colorimeter.

Algae

Algae is monitored in the supply rivers and Deep Creek Dam during the warmer months

(November to March). Nuisance species may impart taste and odour to the water or block

pumps and pipes and some blue-green algae species are even potentially toxic.

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Water Quality Monitoring At Deep Creek Dam

Water quality parameters

are monitored at Deep

Creek Dam on a routine

basis. The intake tower at

the dam has adjustable

intake gates, and these

gates are adjusted to

ensure that the best

quality water is drawn

off.

With storage such as

Deep Creek Dam, the

water would normally

stratify (form layers),

with decreasing

temperature and

dissolved oxygen with

increasing depth. For the

water to remain high

quality, low dissolved

oxygen needs to be

avoided. Therefore, air is

blown into the dam to

both increase the

dissolved oxygen and to

mix the dam to prevent

stratification, and hence

provide a better quality

water.

Deep Creek Dam Intake tower

Other Factors Affecting Water Quality

As pipelines become older there is a build up of material within the pipeline, such as iron,

and also any dirt will accumulate at low points. Pipes within the Shire are regularly flushed

and scoured to remove this material and prevent it being washed through household taps.

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High velocity scouring of

water mains will allow build

up material to be removed

from the pipe system

Water Main between Tuross

River pumping station and

Big Rock reservoir.

Water remaining in reservoirs will allow any silt, etc to settle out, hence with time there is

also an accumulation of material at the bottom of the reservoir. The Shire has an ongoing

programme of cleaning them out to prevent dirty water being drawn out of the reservoir,

which would otherwise occur whenever the reservoir water level dropped low enough.

Several methods are in use predominantly:

Draining reservoir by demand to 1m above reservoir bottom then dumping the final 1m

and hand cleaning;

Cleaning reservoir when full of water using divers or by a remote control vacuum cleaner.

With the exception of Buckenboura Reservoir, all reservoirs within the Shire are roofed to

prevent contamination of the water by bird droppings, dead birds, etc. Reservoir roofs also

stop the water being exposed to sunlight, which would destroy the free chlorine in the water.

END