Clean up of Stover lake

Clean-up of Stover Lake begins with removal of 17,000 tonnes of sediment

A man-made lake near Newton Abbot in Devon, dating to the Georgian Period, is the site of major habitat improvement works that will help to rejuvenate the lake and its surrounding area, returning it to its former glory and benefiting a host of wildlife.

Stover Lake, a ten-acre freshwater lake within Stover Country Park, itself a Site of Special Scientific Interest, is being de-silted after it was found that the lake was in poor condition. The work is being carried out by Murlac, with Fishtek Consulting supervising the work after managing the design and consent process, including the discharge of planning conditions.

Fishtek Project Manager Dr Peter Brunner said: “Poor water quality and accumulated sediment were having a negative effect on Stover Lake. Waterlilies and other aquatic plants were lost, as were numerous invertebrate species. By removing excess sediment and phosphorous and increasing the depth of the lake, we will enable the natural regeneration of aquatic vegetation and see improvements to habitat and water quality.”

According to Peter, 14,000 cubic metres of sediment – about 17,000 tonnes – are being removed from the lake, which will be dried out and reused within Stover Country Park on a 1.4-hectare site earmarked for future tree planting – nearly the size of two football pitches. The area will host a broadleaved woodland with some conifer and native shrub that will give a boost to the ecological diversity of Stover Country Park.

Peter said: “Stover Lake is home to the endangered European eel and other important fish species, so the de-silting work is being done with minimal impact to aquatic life. Dredging operations, combined with environmental factors, can increase temperature and lower dissolved oxygen, which can lead to fish death. The works on the lake are implementing soft starts – running the machinery for five minutes to scare away fish from the area prior to dredging – and are making use of equipment to monitor dissolved oxygen levels and to mix and aerate the water, which will keep dissolved oxygen levels high.”

He said an innovative use of geotextile bags for the drying of removed sediment solved another challenge in containing the New Zealand pygmyweed (Crassula helmsii), a schedule 9 invasive species. Using the geotextile bags will ensure that any removed pygmyweed from the lake will be trapped and unable to photosynthesise and will die off during the drying of the sediment. Before spreading this sediment as topsoil, each geotextile bag will be checked by a qualified ecologist to ensure that any pygmyweed in the bags has been properly eradicated.

It is hoped that by reducing pollution and silt, white waterlilies (Nymphaea alba) – not seen at the lake since 2007 – will re-establish to provide a more diverse habitat for wildlife, such as dragonflies; 28 species of dragonfly have been recorded at Stover Lake to date, and some species have been lost, such as the scarce blue-tailed and small red damselfly, but other species have arrived over more recent years due to global warming, such as the scarce chaser and lesser emperor dragonfly, which has resulted in an overall gain.

Peter said: “It is so valuable when local authorities are able to invest in these projects to maintain these sites because the health of the park, including the lake, is an important asset that needs to be nurtured and maintained for the enjoyment of all. I am sure James Templer, who built the lake back in the 1800s as part of the Georgian designed landscape of the historic Stover Park, would share this vision!”

The de-silting of the lake, which is expected to be completed in July 2024, is part of the wider Restoring Stover Park Project implemented by Devon County Council and made possible with funding from the National Lottery Heritage Fund and National Highways. Fishtek will be further involved in the project in 2025, undertaking post-ecological monitoring of Stover Lake to determine how the lake and its ecology have responded to de-silting.

The wider scheme includes extending the current visitor centre, creating a new community workshop, repairing and conserving the Grade II* listed granite gatehouse, installing new interpretation, creating two new footpaths for the public to enjoy and carrying out improvements to the car park. It will also see a 100 m portion of the Serpentine Lake restored so that it appears the same as it does in 19th century etchings of the site.

Devon County Councillor Andrea Davis, Cabinet Member for Climate Change, Environment and Transport, said: “Stover Country Park receives some 180,000 visitors a year, with Stover Lake being key to the numbers of visitors coming to the park and their enjoyment of the environment. Restoring this popular ecological feature towards favourable condition will provide an ecologically rich and diverse lake for future generations to continue to enjoy.”

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