Shiplake and Bray Locks will be shut for up to four months
Several closures will be in place on the River Thames over the next six months while 13 of the Thames Valley's locks get a £5.1m upgrade.
The Environment Agency (EA) is investing in new lock gates, improved walkways and mooring facilities.
Work will be carried out in stages between November and February next year and 10 locks will be temporarily shut.
The largest projects are at Shiplake in Oxfordshire and Bray Lock on the Buckinghamshire-Berkshire border.
A total of £1.35m will be spent at the two sites, where work will be carried out to replace lock gates and repair lock chambers.
At Iffley Lock in Oxfordshire, Marlow Lock in Buckinghamshire and Whitchurch Lock - which spans Berkshire and Oxfordshire, the EA will install "out of hours public power", which will allow boaters to operate the lock at half power when the lock keeper is not available to help.
When that work is completed at the end of the year all the agency's hydraulic locks will be operational out of hours.
Other work to be carried out includes new facilities at Mapledurham Lock in Oxfordshire, where a pump-out, a chemical toilet disposal facility and a drinking water tap will be installed.
Work is already under way to upgrade the short stay moorings at Abingdon, Oxfordshire, and improvements are also being made at Culham in Oxfordshire, and Hurley Lock in Berkshire.
Paul Power, Environment Agency engineering manager for the River Thames, said: "Apart from Shiplake and Bray, the lock closures are fairly short."