A new study confirming the impacts of groundwater pumping on Boundary Creek will allow Barwon Water to develop an improved flow restoration plan based on solid scientific data.

The study is part of a comprehensive groundwater monitoring program launched in 2013 to help inform the corporation’s Barwon Downs borefield licence renewal application, which is due to be submitted to Southern Rural Water in late 2017.

Barwon Water General Manager Strategy and Partnerships Carl Bicknell said while it has been known for some time that borefield pumping was connected to flows in Boundary Creek, the level of interaction had not been fully understood.

“As a condition of our current groundwater licence we have released supplementary flows into Boundary Creek. However, we know these flows have not always made their way to the lower reaches of the waterway,” Mr Bicknell said.

“We now have results of a thorough scientific study that provides answers we can be confident in, allowing us to examine ways to restore flows that will compensate for the operation of the borefield,” he said.

The borefield is a crucial supplementary water source for the region when surface storages are low. It consists of six bores that pump groundwater from an aquifer 300 to 630 metres below ground.

In 2007, at the height of the worst drought on record, Geelong’s water storages dropped to just 14 per cent and the borefield provided up to 70 per cent of the city’s daily usage.

Mr Bicknell said the new data was a result of a major update to the groundwater model for the Barwon Downs area.

The model meets the highest ranking under Australian guidelines and is sophisticated enough to separate natural climate-related impacts from past groundwater pumping.

It found operation of the borefield over the past 30 years was responsible for two thirds of the reduction in base flow from the aquifer into Boundary Creek. The dry climate experienced over the same period accounted for the remaining third.

The model also shows the lower sections of Boundary Creek would likely have no flow periods during summer regardless of groundwater pumping. However, pumping has increased the frequency and duration of no-flow periods in lower reaches of Boundary Creek.

The data confirmed there was no predicted impact to vegetation outside the Boundary Creek catchment as a result of groundwater pumping.

Mr Bicknell said further technical studies were underway to assess the effect of a range of alternative borefield operating regimes on flows in Boundary Creek and measures to address the issue of acid water release from Big Swamp into Boundary Creek.

To find out more about the licence renewal project and access technical reports please visit our document library.