The river Granta has historically been modified by straightening and dredging, which removes habitat features and means that the river is less able to maintain a variety of habitat niches (need flow diversity with faster areas to keep gravel clean and deeper pools for fish refuge in hot weather etc).

On a stretch near Babraham a number of weirs prevent fish from moving upstream and also disrupt sediment transport within the river, which means it can’t function naturally. Recent restoration work here has seen two weirs removed - one intact with much trapped bed material behind it, and the other defunct. Habitat creation was achieved by adding woody material and gravel to the channel, along with work to reshape banks plus the creation of a scrape and a backwater.

The Trust's Water for Wildlife Officer Ruth Hawksley explains: “Our chalk streams suffer from the fact that the land is pretty flat, meaning a very limited gradient along the course of the river; by removing the weir we could use that head-drop to energise a longer reach of river. We’ve removed some big lumps of concrete from a defunct weir and added almost 40T of gravel to the river. We dug an experimental scrape and hinged a big willow over the channel to encourage flood water into it, and also created a new backwater nearby which holds a small amount of water and should do pretty much all year, and a ledge was created from hazel bundles.”

The work was by a collaboration of organisations, with Rob Mungovan from the Wild Trout Trust, volunteers and funding for contractor work via the Environment Agency, Cambridge Water and Anglian Water - there are more weirs upstream and downstream and this is part of a wider ambition with a phase two expected, but for now it has already benefitted the river.

Save our chalk streams - take action

England's chalk streams are one of the rarest habitats on earth, yet many of our chalk stream rivers are now polluted, dirty and choked by pollution, threatening the wildlife that call them home and the people that rely on them for wellbeing – they need new legal protections if they are going to stand a chance of recovery. Take action with Wildlife Trusts and partners.