Page 86 - AGL Sustainability Report 2011

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AGL Energy Limited 84
Managed water
In addition to the consumption of water resources, AGL
also makes important non-consumptive use of water,
including water drawn from the Port Adelaide River to
cool the Torrens Island Power Station, and the water that
is passed through hydro power stations. AGL takes its
responsibilities as short-term steward of water resources
seriously and manages this carefully.
AGL’s use of water for cooling purposes at Torrens Island Power
Station is regulated by its Environment Protection Authority licence.
The average temperature increase from the cooling water inlet to
the cooling water outlet is required to be less than 10°C. An external
consultant audits and validates compliance with this requirement
on a two-yearly basis. The last audit report was issued in December
2010, and found AGL to be compliant with requirements.
AGL’s hydro power generation assets are located across Victoria
and New South Wales. The different assets/schemes operate under
different water release arrangements as described below:
Mountain Streams Scheme (Royston, Rubicon, Lower
Rubicon and Rubicon Falls power stations) and the Kiewa
Scheme (Bogong, McKay Creek, Clover and West Kiewa
power stations), Victoria
– AGL holds non-consumptive
bulk water entitlements with the Victorian Department of
Sustainability and Environment (DSE) to use all infows to the
catchment for power generation at its power station assets. The
entitlement sets minimum and maximum water fows and rates
of change of releases, although AGL has discretion within these
boundaries as to how and when water is released within the
Dartmouth and Eildon, Victoria
– AGL holds water
agreements with Goulburn Murray Water (GMW) to generate
electricity from all irrigation releases from these storage dams
which are owned and operated by GMW. AGL owns regulating
pondage downstream of these power stations. Under the water
agreements, GMW specifes what fows it wants in the river
system downstream of AGL’s pondage and so using its pondages,
AGL has some fexibility in how this is achieved. Under the water
agreements AGL has an entitlement to use a specifed volume of
water outside of the irrigation season. GMW must be notifed of
any such releases so they can allocate the water appropriately to
users downstream.
Cairn Curran and Yarrawonga, Victoria
– AGL holds water
agreements with GMW to generate electricity from all irrigation
releases from these storage dams which are operated by GMW.
Pindari, Copeton, Burrendong and Glenbawn power
stations, New South Wales
– AGL operates these power
stations under a water agreement with New South Wales State
Water that entitles AGL to generate electricity from all irrigation
releases of water from the storages. The release of water is
dictated by the needs of irrigators, not AGL, although AGL
has the right to produce power from any irrigation releases.
Where AGL has discretion for releases of water (i.e. where water
release is not dictated by irrigation needs), potential environmental
impacts are managed by controlling river discharges to within the
agreed rates of rise and fall and minimum and maximum flow rates
as specified by the relevant authority or agency.
An important annual activity undertaken in the Mountain Streams
and Kiewa schemes is desilting of some of the storages and dams
to maintain capacity and, in turn, the operating flexibility within
the schemes. An environmental working group, (comprising AGL,
the Environment Protection Authority Victoria, Victorian DSE,
Parks Victoria, Victorian Department of Primary Industries, local
catchment authorities and the Freshwater Ecology section of the
Arthur Rylah Institute for Environmental Research), meets annually
to review processes, monitoring data and the annual works program.
To minimise the environmental impact of the desilting operations,
the activity is conducted during higher flow winter months. Silt
is removed by both direct flushing into the river system and by
excavation. Environmental parameters agreed by the desilting
working group are monitored at a variety of downstream locations
at a frequency of 15 minutes to one hour depending on location.
This process has been undertaken for more than 10 years and annual
studies indicate that there have been no detectable impacts on the
ecology of the river system, as indicated by long-term monitoring
of macro-invertebrates and blackfish undertaken by the Freshwater
Ecology section of the Arthur Rylah Institute for Environmental
Research at DSE for AGL.
During FY2011, AGL made non-consumptive use of approximately
666 GL of water drawn from the Port Adelaide River to cool the
Torrens Island Power Station, an almost 20% increase compared
to FY2010. Over the same period, generation from the Torrens
Island Power Station increased by 10%.
Over 4,000 GL of water passed through hydro power stations
during FY2011, compared to 466 GL in FY2010. The significant
increase can be attributed to unseasonably high rainfall experienced
across relevant catchments in Victoria, and indeed much of the
north and east coast of Australia. Bureau of Meteorology data
indicates that during calendar year 2010, Victoria experienced its
fifth wettest year on record
Increased water flows through AGL’s hydro power stations during
FY2011, particularly associated with the flood events in September
and December 2010, have resulted in increased volumes of silt
removed during FY2011. During FY2011, 40,000 cubic metres of
silt were removed from the Rubicon/Kiewa Hydro Scheme.