Earth First | Raising Wyangala Dam wall will not solve all problems

Bev Smiles

December 13 2021

A larger Wyangala Dam cannot solve all problems and will create many new ones.

Inland Rivers Network continues to question the rationale behind spending up to $2 billion dollars of public money on raising the Wyangala Dam Wall when the purpose of the proposal is unclear.

With the current floods in the Lachlan Valley there are conflicting calls for this proposal to provide both increased water security and improved flood mitigation.

These competing roles require different dam management and water sharing arrangements. Increased water security requires a full dam while improved flood mitigation requires lower levels.

The recent high rainfall events in the upper Lachlan catchment from August to November have demonstrated that the proposed larger dam would not have prevented the floods at Forbes.

Analysis of inflows to Wyangala Dam since it first filled in August, based on real time inflow reporting on the WaterNSW website, shows that the proposed larger Wyangala Dam would have filled and spilled in early October.

Also, analysis of inflows to the Lachlan River from tributaries below the dam showed that Wyangala Dam releases from a larger dam would still have occurred at the same time the increased tributary inflows from the Belubula River, Boorowa River and other swollen water sources below the dam entered the Lachlan River upstream of Forbes.

The proposed increased capture of 650 billion litres of water would not have solved impacts of flooding at Forbes and downstream during these highly unpredictable large rainfall events.

Inland Rivers Network looks forward to the release of the next stage of the draft Lachlan Regional Water Strategy that will consider the impact of climate change on the region and prioritise a range of water security options.

The NSW Government has announced that alternative water security options will be considered in the final business case for a larger Wyangala Dam.

This is a welcome step in the assessment process for this very large and impactful proposal.

While the recent floods have been disruptive and damaging to settlements and crops on the floodplain, the rainfall has been recuperative for the natural environmental following the recent intensive drought conditions.

Depleted soil profiles and groundwater sources have been replenished.

Native fish have good breeding conditions and the best waterbird breeding since 2016 is occurring in the Lachlan wetlands.

The Listening to the Lachlan Conference in Forbes in February will discuss many of these issues.

Inland Rivers Network president Bev Smiles

https://www.cowraguardian.com.au/story/7548227/earth-first-a-larger-dam-will-not-fix-all-problems-in-the-lachlan/

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