Behind the scenes at Slaithwaite Reservoir

To mark this milestone we're releasing new ‘behind‑the‑scenes’ images to show the scale and complexity of the engineering works.

Building climate resilience

The spillway functions as the reservoir’s overflow channel, safely carrying excess water away when levels rise. The new, modern structure is being built with a significantly greater capacity to cope with increasingly frequent extreme weather events, strengthening the reservoir’s safety, reliability and long‑term climate resilience.

The statutory maintenance and improvement works will strengthen the centuries‑old structure and enhance the performance of the overflow spillway. The project also includes repairs to the dam, new stone cladding to blend the structure into the landscape, and improvements to access and fencing around the site.

About Hill Top Reservoir

Hill Top Reservoir can hold over 300 million litres of water – around the same as 120 Olympic‑sized swimming pools – and at almost 22 metres high, the dam may have been the tallest of its time.

Built 225 years ago by renowned canal engineer Benjamin Outram, the reservoir was created to supply water to the Huddersfield Narrow Canal, a vital industrial route in the 18th and 19th centuries. Today, it continues to feed the canal network and remains a much‑loved leisure spot for walkers and anglers. These essential upgrades will ensure the reservoir can continue supporting both the canal and the local community for generations to come.

The main construction phase to improve the spillway will last around 13 months, with completion expected by early summer 2027. Water levels will be lowered at times to allow work to take place. We aim to keep footpath access open wherever possible, with alternative routes clearly signposted when needed. 

The work comes at a time when we are facing challenges from more extreme weather, driven by a changing climate, affecting the nation’s ageing canals. 

More important than ever

Sean McGinley, our Yorkshire and North East regional director, said: “With such unprecedented weather conditions this year, our charity’s significant programme of investment to improve our large reservoirs across the country is more important than ever. This work will help to secure the long-term future of Hill Top Reservoir as an important resource for the Huddersfield Narrow Canal and in turn the Huddersfield Broad Canal.

“Originally constructed in the late 18th century, this reservoir, like much of our historic network, requires ongoing maintenance and upgrading to meet present day standards.  These reservoirs help to feed our canals and maintain water levels along the inland waterways. Their function is proving increasingly important to help us manage water levels during more frequent extreme weather conditions brought about by climate change, with prolonged dry weather and wet winters.”

Meeting present day standards

We look after the reservoir and Huddersfield Narrow Canal has commissioned civil engineering company JN Bentley to undertake the works, to ensure that historic reservoirs like this are meeting present day standards (as required by the 1975 Reservoirs Act).

We're undertaking a significant programme of investment across their reservoirs to ensure they stay resilient to climate change and comply with the strict legislation that applies to all large reservoirs. Over £27 million was spent on resilience works last financial year at 19 of our reservoirs.