The River Thames is to benefit from a £3.8m upgrade.
New lock gates, better mooring sites and improved non-powered boat access will be created later this year.
Eighteen structures will benefit in all with the largest projects at Hurley and Sandford in Berkshire, where locks will get £1.5m worth of improvements.
The work, across Oxfordshire, Surrey, Berkshire and Buckinghamshire, will see 15 locks affected by temporary closures between October and March.
Paul Power, from the Environment Agency, said: "Following six years of hard work and continued investment the navigation infrastructure along the River Thames is in good shape.
"We have a full programme of works this year and I'm sure boaters and other visitors will enjoy the improvements next boating season and for many years to come."
A map detailing all the work has been posted on the River Thames website and will be regularly updated.