Thames Water has begun work to replace a leaking water pipe under Osney Bridge which was damaged by an Environment Agency boat in April 2021.
The work is being completed in three stages with the first stage starting on March 11.
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It is expected the first stage will be completed by the end of the month.
Following the damage in 2021, the water company installed a temporary pipe to maintain the water supply.
This runs above ground in the cycle lane of Botley Road, across Osney Bridge.
A Thames Water spokeswoman said: “We are sorry for any delays while we carry out a water mains pipe replacement on Botley Road near Osney Bridge.
“Due to the complexities of the location, we are carrying out the work in three stages.
“Our teams started stage one on March 11, which is expected to be completed at the end of the month.
“During this time, temporary traffic lights have been in place and we apologise for any inconvenience to local residents and motorists.”
Significant elements of phases two and three can only be undertaken during the River Thames closure window from November to March each year, say Thames Water.
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This means the final stages of the work are scheduled to take place between November 2024 and March 2025.
It comes as Botley Road has been closed at the railway bridge due to ongoing works to improve the train station.
This separate work is being carried out by Network Rail and is due to be finished in October.
Work on the station and railway upgrade had to be paused in June after contractors unearthed an inverted brick arch, thought to be part of the original Victorian drainage system.
A Thames Water statement said: “Due to the discovery of a Victorian inverted brick arch below the Botley Road bridge area, the Network Rail project is significantly delayed, meaning the road closure is continuing through to October 2024.
“This has caused a significant delay to our project.
“We held a meeting with all key stakeholders, including Network Rail, Oxfordshire County Council and the Environment Agency.
“We proposed an alternative solution to keep the project moving forward.
“This is to divert the temporary water main in the eastbound cycle lane of Osney Bridge across the River Thames via a temporary scaffold pipe bridge.”