West Barwon continues to spill with high rainfall

Flows into West Barwon Reservoir continue to sustain high water levels in the reservoir. We are not currently transferring to the Wurdee Boluc Reservoir as both reservoirs are at capacity. Our three month climate outlook is indicating that there is a chance of higher than average rainfall between December and February which could result in further spills to the West Barwon River over summer. When a reservoir is spilling it is behaving as a natural system.

Our reservoirs are not designed for flood mitigation, and instead are designed to fill and spill during wet periods. The water that is captured is used for water supply purposes and passing flow releases in accordance with our bulk entitlement requirements. West Barwon Reservoir also captures water for environmental flow releases in accordance with the environmental entitlement which is managed by the Corangamite Catchment Management Authority (CMA) on behalf of the Victorian Environmental Water Holder.

Geelong Storages are now at 99.1%, approximately 1.6 percentage points higher than the same time last year and the highest storages have been in the last 10 years.

Preparing for the summer

With the possibility of another wet summer our operations teams are considering transferring water from the West Barwon Reservoir to Wurdee Boluc throughout January, something we do not normally do due to lower storage

levels over summer. The transfers would go for around six-weeks and aims to reduce the likelihood of further spilling over summer. This management of transfers is carefully considered every year and is dependent on storage levels and rainfall. We know as our climate becomes hotter and drier, our weather patterns are becoming more unpredictable which is why we must adapt our operations to suit conditions.

Environmental vs passing flows

We often reference environmental flows and passing flows when talking about our reservoirs. They are important aspects of water management, but what exactly is the difference?

Passing flows are the minimum flow of water we must allow to pass downstream of our reservoirs or extraction points. The passing flow required varies depending on the waterway, natural flows, time of year and storage levels.

Environmental water flows refer to additional water that is released to support ecological health, usually over the dry summer months. The Corangamite CMA on behalf of the Victorian Environmental Water Holder advise actual environmental releases required and take into account the passing and natural flows already present in the river. No environmental water has been released since July 2022 due to the above average rainfall.

Did you know it can take five days to transfer water?

Water is commonly transferred from the West Barwon Reservoir to the Wurdee Boluc Reservoir via a 57-kilometer channel. This channel relies completely on gravity so it can take up to five days for the water to travel the 57 kilometers, and it can only be transferred one way. That’s one of the reasons why we need to plan our water transfers so carefully.