Waterway Notices / Navigation Closure – Grand Union Canal: Lock 46 (Cowroast Lock) to Lock 39, Including Lock 45 (Marsworth Flight)

Effective from Monday 5 October 2026 Following our continued monitoring of exceptionally low rainfall levels, and the need to mitigate the risk of Blue Green Algae in two of our reservoirs, it has become necessary to restrict navigation while maintaining a limited daily window for essential boat movements. As a result, the locks detailed above will be opened for navigation between 10:00am and 2:00pm each day. The locks will then be secured at 2:00pm, with the flight fully closed at 3:00pm to allow all vessels sufficient time to pass through. The first day of this closure will be 2:00pm Monday 5th October Despite the considerable efforts of our operational teams, rainfall has remained significantly below the long-term average. Consequently, water levels within the Tring Reservoir Group have continued to decline as a result of canal water demand. This position is now unsustainable, with only sufficient resources available to maintain water levels across the Grand Union South (GUS). In addition, the prolonged period of warm weather has led to blue-green algae affecting two of our principal feeder reservoirs, further reducing the volume of water that is operationally available for canal use. Closure Arrangements from Monday 5 October 2026

• Lock 46 (Cowroast Lock): Open from 10:00am to 2:00pm.
• Locks 45 to 39 (Marsworth Flight): Open from 10:00am to 2:00pm, with a final one-hour passage window before the flight closes fully at 3:00pm.

We ask that boaters only navigate when absolutely necessary. Water conservation is now a priority, and unnecessary movements will increase water demand and may accelerate the need for a full closure. We fully appreciate that this will be disappointing news for those planning to cruise this section of the canal. These restrictions have not been introduced lightly. However, they are essential to protect our increasingly limited water resources, safeguard the canal infrastructure and ecology, and ensure that the remaining available water is used as effectively as possible. We hope to reopen the canal as soon as conditions allow. However, this will depend on a sustained period of rainfall over several weeks rather than a single episode of heavy rain.      We sincerely appreciate your patience, understanding, and continued support during this exceptionally challenging period.