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Cockatoo community group work continues

15 May 2018

The Cockatoo Lagoon Community Working Group has recently agreed to investigate two options to secure water supply for the region’s irrigators and the environment.

The 11-member community working group was established in January this year through a public call for members, and has met three times over the past three months.

Chair of the Community Working Group and local irrigator Neville Goulding said the group is working hard to find suitable outcomes that meet varied interests.

“The creek has no spare capacity at the moment, and the capacity of Cockatoo Lagoon is also declining. If the creek capacity continues to decline then rationing will occur and nobody wants that, ” he said

“The capacity constraint has the potential to limit water allocation deliveries for both irrigators and the environment during peak periods. This is a problem particularly for irrigators downstream of Gunbower, who can already experience waiting periods of several days to access water even in an average season such as the 2017-18 irrigation season.

“Irrigation is worth a lot of money to our region, and we have a great opportunity to help our irrigators secure capacity with a bucket of money that is coming from the environment, to not only secure delivery  capacity for our irrigators but also ensure there is enough capacity to water the Gunbower Forest as well.

GMW Customer Operations General Manager Scott Barber said Gunbower Creek and the associated lagoons are natural waterways and therefore constantly changing.

Over 100 years, natural fluctuations and processes have included erosion, trees falling in, sedimentation and the introduction of weeds, which have thrived. Regulation of the water has also changed its natural course.

“These impacts have resulted in a gradual reduction in the maximum flow capacity of the creek.

“Historically, the creek passed 1650 ML/day below Gunbower. Below Gunbower is the reach of the creek that is the subject of current investigations.  At this point in time, flows downstream of Gunbower are restricted to 800 ML/day.

”The delivery of environmental water has not had any adverse impact on the delivery of water to irrigators. We continue to abide by our service standards of providing water within 48 hours of ordering it.”

One of the options to increase the capacity of the creek is to remove Thompson’s Weir and look at other complementary works. Removing the weir would cause lower water levels upstream of the weir, and mean that inflows into Cockatoo Lagoon may be impacted during low flows in the creek. Options are being considered to manage this.

Another option under investigation, which was presented by community members on the group, is to remove Thompson's Weir and replace it with a gated weir upstream near Cockatoo Lagoon.

The condition of Cockatoo Lagoon is declining and the long term viability of the lagoon as an irrigation water carrier is being compromised by weed growth and siltation. Over the past few decades the numbers of catfish, platypuses and turtles have been going backwards. The options being investigated present an opportunity to look at protecting the values of Cockatoo Lagoon as well.

“If we do nothing, irrigators in the whole Torrumbarry irrigation system, the community, and the environment will be worse off,” Mr Goulding  said.

“Both options are being investigated to see how they compare in terms of benefits for the environment and irrigators, and how they stack up financially."