Chalk stream restoration paves the way for a historic reintroduction of endangered water voles to Surrey
Extinct in the county for over 20 years, water voles have been released by South East Rivers Trust at Chamber Mead Wetlands and on the Hogsmill River, after restoration work improved the habitat condition enough to welcome these iconic river rodents back
31/07/25
Blog
In late July 2025, the Rivers Trust were delighted to join South East Rivers Trust as a new population of 50 endangered water voles was released at the Chamber Mead Wetlands and the Hogsmill River. They will be the first water voles living in the wild in Surrey for over 20 years.
South East Rivers Trust, The Rivers Trust, Epsom & Ewell Borough Council, local volunteers, MPs and more gathered to watch as several of the 50 water voles were carefully placed in soft-release pens; metal boxes dug into the riverbank, filled with bedding and some food. These pens are bottomless, allowing the water voles to get acquainted with their new surroundings and dig their way out over the next few days. Males and females, bred by Wildwood Trust, were released by Citizen Zoo in alternate pens along the Hogsmill and in the wetland, to maximise the voles' chances of finding a suitable romantic partner as they emerge and begin to grow the population.
Water voles are an iconic river species (the inspiration behind Wind In the Willows character, Ratty', no less, and are a keystone species with important roles in well-functioning river ecosystems. These keen herbivores are skilled at distributing seed around their patch and facilitating a biodiverse flora, as well as being a vital part of the local food chain and creating habitat niches for other species with their burrowing.
The Chamber Mead Wetlands were created as part of a partnership project improving the condition of the Hogsmill, a rare urban chalk stream blighted by, among other pressures, high levels of urban run-off. The new wetland, strategically positioned between the Hogsmill and a key stream that brings this pollution from the surrounding residential area, acts as a natural filter. It removes some of the chemicals and sediment from the Green Lane Stream's dirty water before it reaches the chalk stream, easing pressure on the Hogsmill and allowing it to function more naturally.
The wetland also slows the flow of water, holding it on the site for longer and allowing biodiversity to flourish, including in times of low and high rainfall. Recent surveys found nine different species of dragonfly on site, and the newly regenerated green space is regularly enjoyed by the local community.
Today's event celebrated the resulting thriving ecosystem. Water voles went extinct locally in part due to habitat decline, but thanks to restoration efforts, the area is now a suitable home for this iconic keystone river species. Volunteers will now help to carefully monitor the population.
Chamber Mead Wetlands are a fantastic example of a partnership working together to deliver a nature-based solution project; by doing so they created an incredible space that offers myriad benefits to the freshwater environment, to the local community, and now, to its new resident water vole population. The wetlands are part of The Rivers Trust's wider Replenish programme, which aims to restore millions of litres of water in this and other local catchments. Find out more.