A GROUNDWATER tunnel at Gormans Hill last used 70 years ago could be part of a long-term plan to secure the city's water supply, according to a retired engineer.
Subscribe now for unlimited access.
$0/
(min cost $0)
or signup to continue reading
Norman Wise, a former geotechnical and regional engineer who formerly worked with the NSW Office of Water, is calling on Bathurst Regional Council to explore options to ensure the city's water security.
He has met with mayor Robert Taylor to discuss his suggestions, which include utilising the 500-metre long groundwater tunnel, which was used by Bathurst City Council from 1889 to 1950.
The tunnel was built from the site of the old pumping station near the current water filtration plant at Gormans Hill, east under the Macquarie River floodplain.
The brick-lined tunnel is two metres high by 1.5m wide. The 20m deep tunnel was dug through solid granite bedrock under the floodplain and drew groundwater from a deep sand and gravel alluvial layer formed during the last ice age some 15,000 to 40,000 years ago.
Holes drilled in the tunnel roof up into the gravel aquifer also allowed groundwater to drain into the tunnel.
Mr Wise said, sadly, the pumps have sat unused since 2004, but said it would be feasible to re-equip the shaft again to draw groundwater from the tunnels in the future.
He said the tunnel, when in use, supplied between one and 3.6 megalitres of water per day, dependent on the river flow and height.
He said the tunnel was the only source of water for Bathurst in the early part of last century whenever the Macquarie River stopped flowing.
IN OTHER NEWS AROUND BATHURST:
He said he, along with Richard Cook, a retired senior hydrologist, have spent many years studying the effects of climate change and its impact on streamflow, and now is the time for Bathurst Regional Council to act on water security, using the groundwater tunnel and other methods.
Mr Wise said water availability is at risk thanks to the combined effects of climate change.
"The impact of higher temperatures, evaporation and decreased rainfall has reduced streamflows," he said.
"The Macquarie River has supplied Bathurst's town water since the mid-1880s. In summer, Bathurst often relies on Chifley Dam and Campbells River as a back-up supply.
"But the Campbells River streamflow tap into the Chifley Dam has been effectively reduced by over 50 per cent since 1990, due to a reduction in rainfall in the dam catchment, combined with increased temperatures and evaporation."
Mr Wise said with the CSIRO forecasting a further 30 per cent decline in streamflow in the Murray-Darling Basin over the next 30 years, together with a 10 per cent decline in rainfall, the situation is grim.
"This will mean less reliable flows into Chifley Dam. The security of Chifley Dam and the town water of Bathurst will be significantly reduced," he said.
"Considering the city almost ran out of water in the last drought of 2019-2020, water security is imperative."
To spread the risk of water insecurity, Mr Wise is calling on Bathurst's water supply to be supplemented by adding groundwater to the supply from the groundwater tunnel at Gormans Hill.
"The Macquarie River floodplain, alluvial groundwater source, supplied up to 3.6ML a day and was vital for the town whenever the Macquarie River stopped flowing," he said.
"This could have provided up to 36 per cent of the town consumption of 10ML a day during the 2019 and 2020 drought."
Mr Wise has also called on council to implement rainwater harvesting from at least 8000 homes in Bathurst using storage tanks large enough (10,000-plus litres) to hold one month's supply of water.
"This could supply up to three megalitres a day during a drought, which could have met 30 per cent of the town's water demand during the 2019-2020 drought," he said.
Mr Wise said larger rainwater harvesting schemes could extend to public, commercial and industrial buildings in Bathurst.
Finally, in a drought, he said council could substitute effluent wastewater for raw water use on parks and gardens.
"Currently, Winburndale Dam supplies up to three megalitres a day of raw water for parks and gardens and this amount could have provided up to 30 per cent of the town demand during the 2019-2020 drought," he said.
Mr Wise said the above three water supplements could have provided more than 90 per cent of the town's water demand in the last drought, but said council needs to act now to secure the city's future water security.
"To mitigate for a reduction in water supplies due to climate change, a strategic approach is needed to adapt to less available water supply in the future," he said.
"Planning for these changes needs to start now as often there are significant lead times before projects are completed."
Have you say on this issue with a Letter to the Editor......
Our journalists work hard to provide local, up-to-date news to the community. This is how you can access our trusted content:
- Bookmark www.westernadvocate.com.au
- Make sure you are signed up for our breaking and regular headlines newsletters
- Follow us on Twitter
- Follow us on Instagram
- Follow us on Google News