A 44-year-old man has been flown to the Royal Melbourne hospital after the ute he was in rolled near the Ballan Mineral Springs.
The CFA said the alarm was raised at 6.32pm (Sunday) to Shaws Rd, just inside the Bostock Reservoir park.
Police said a 39-year-old woman who was also in the ute was treated and taken by road to Ballarat Health Services.
It is understood the east-bound ute swerved on the gravel road several times, hitting a wooden post and the metal gates to the Barwon Water property.
Ballan CFA sent four vehicles including a rescue truck and had the scene under control within 10-minutes.
Bacchus Marsh Highway Patrol officers are investigating the cause.
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