Introduction
The Wellington Dam Water Recovery
Project is an alternative to the decision by the Government
Of Western Australia to build either another reverse
osmosis plant at Rockingham or its preferred option
of drawing water from the south west Yarragadee aquifer
near Busselton, both of which are designed to deliver
45GL of water to Perth water users.
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Wellington Dam is the largest
and safest dam in the south west (in terms of
inflow) with a capacity of 186GL and published
average annual inflow of 144.8 GL (see Storage
Statistics). The dam was built in 1933 to
provide water to the Great Southern Towns Water
Supply Scheme and to provide irrigation water
to farmers along the coastal strip.
Salinity in the dam began to rise
in 1960 and increased to such an extent that in
1989 a new dam (Harris Dam) was built. This dam
took over the supply of water to towns in the
Great Southern. Since then Wellington Dam
has only been used to supply up to 68GL of irrigation
water annually.
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The saline water flowing into the dam
from the Collie river is heavier than fresh water and
falls to the bottom of the dam forming a large (40GL)
slug of saline water. Each year in an endeavour to reduce
the dam salinity level, the Water Corporation scours
the saline slug through a large gate valve at the bottom
of the dam, and discharges it out to sea (see photo
on home page).
This operation usually commences in June/July
and continues until late October. This
saline water is discharged at the rate of 450,000 tonnes
per day, (a tonne of water for every house
in Perth, per day). See
Water Corporation press release 2003.
This process has been undertaken continually
over the past 20 years, with discharges of between 20-40
GL annually. This water is being discharged to the sea
and wasted.
This proposal is designed to take the
saline scour water, by pipeline, vertically down the
Darling Scarp to Brunswick (approx. 20kms).
At Brunswick the water is to be treated
by a reverse osmosis plant (RO) and then piped 18 kms
to Harvey and connected to the pipeline supplying Perth.
The process will result in the water's
salinity level being reduced from 1500ppm to 50ppm.
Perth's Dams have an average salinity level of approx
450ppm.
The environmental bonus for the project
is that the RO operation does not require any significant
power, saving an estimated 200,000 tonnes of carbon
dioxide from going into the atmosphere. (see schematic
drawing below).
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