1 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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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