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The charity making life better by water

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A once in a lifetime river restoration project

We’re working on an exciting conservation and engagement project to open up Britain’s longest river, for both the rare fish that depend on it and communities who live alongside it.

A once in a lifetime river restoration project

Unlocking the Severn was an ambitious river restoration and engagement project, delivered by an incredible combined effort between the Canal & River Trust, Severn Rivers Trust, Environment Agency and Natural England. Our project has restored connectivity for migratory fish on the UK's longest river and engaged thousands of people with the fascinating natural, cultural and industrial heritage of the Severn.

Twaite Shad

Introducing...the shad!

The hero species of Unlocking the Severn is a fish you might not have heard of: the twaite shad. Shad are a member of the herring family. Each year these fish undertake an epic migration from the sea into freshwater to spawn. Their migration up the River Severn tends to take place in May, earning them the nickname the "mayfish".

Shad were once seen migrating upstream in their hundreds of thousands. The construction of weirs in the nineteenth century brought huge advancements in society, enabling the transportation of more goods up the River Severn to support the industrial revolution. Unfortunately the shad paid the price.

Shad don't have the ability to leap over obstacles in the river, unlike salmon, which have adapted to swim past boulders and waterfalls as they travel upstream to spawn. Unable to jump the weirs, the population of shad crashed. By the beginning of the project, they were one of the UK's rarest fish.

Providing safe passage

Diglis fish pass, Worcester

By constructing four large fish passes on the River Severn, and modifying two weirs on the River Teme, Unlocking the Severn has unlocked 158 miles of river for fish. The image shows Diglis Fish Pass in Worcester, one of the 4 fish passes on the River Severn. It is a ‘deep vertical slot fish pass', formed of a series of ascending pools. Each section of the pass is 20cm higher than the one before, which allows the shad to swim up above the weir in small, manageable steps.

As well as helping the shad, this allows free passage for other important and endangered migratory fish species, such as salmon and eel. Having more fish eggs and very young fish (fry) in these higher areas of the river - including shad spawning for the first time in nearly 180 years - will also provide more food for insects. More insects and young fish on the river provide food for other animals and birds. This positive effect cascades through the food web and benefits all the wildlife in the river's ecosystem.

A huge success story for wildlife

Scientific monitoring results from the shad migration in 2022 have shown that shad have successfully navigated all four fish passes on the River Severn. eDNA data, collected in collaboration with Natural England, has shown the presence of shad above the 4th and final fish pass at Lincomb in Worcestershire. The evidence proves that shad have accessed key spawning grounds once again!

Excitingly, 25 species of fish had been recorded using Diglis Fish Pass by the end of 2022. This includes other rare or endangered migratory species, such as salmon, eel and lamprey. We are thrilled to see so many species benefitting from a reconnected river.

A group of people pointing at an underwater window

Reconnecting communities with the river

In bringing life back into the upper reaches of the river, we also wanted to deepen local people's connection with the Severn. We believe that the river can enrich lives and provide a unique environment to boost wellbeing. Therefore it was important to give local people, of all ages and backgrounds, inspiring experiences and new insights into the natural world and our relationship with it.

The fish pass at Diglis, near the centre of Worcester, was the biggest deep vertical slot fish pass in England and Wales at time of construction. Most exciting of all, it includes a unique underwater viewing window. This fascinating perspective of the wildlife living in the river has already begun to inform and inspire scientists and visitors, and will continue to for years to come.

The visitor centres at Diglis Island and Diglis Fish Pass were opened by HRH The Princess Royal in October 2021. In our first year, over 7,000 people visited Diglis Island and Fish Pass through tours, open days and events. The visitor season is between March and October. Tours and activities take place on select days with the help of our volunteers. You can find out more about booking a visit below.

Thinking about the future is just as important as the structural work we have done on the river. That's why our heritage and science programme was vital for reconnecting millions of people with the river, helping them to learn, develop skills and get creative. Unlocking the Severn engaged over 65 million people and benefitted from over 14,500 volunteering hours. Over 6,000 schoolchildren were engaged with the project through in-person activities and visits

The support of volunteers

Our volunteering teams, based at Diglis in Worcester. continue to support the legacy of the project. We continue to welcome new volunteers, so if you are interested in leading tours of Diglis Island & Fish Pass, helping to deliver our school visits, or would like to support the project in a practical volunteering role, head over to the Canal & River Trust Volunteering webpage to see the opportunities available.

Last Edited: 26 April 2023

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