PROJECT

Charvil Meadows

Over a two-week period in late September/early October 2020, the South East Rivers Trust converted an area of grassland in the north eastern corner of Charvil Meadows, owned by Wokingham Borough Council, into a backwater habitat.

This essentially meant creating a large pool, adjacent and connected to the River Loddon, to act as a refuge for wildlife against potential pollution from the main river in particular.

Charvil Meadows backwater connected to the Loddon

Charvil Meadows backwater completed and connected to the River Loddon

Electrofishing to assess the Loddon

To a casual observer, the River Loddon at Charvil Meadows might have felt like a wild and diverse part of the river. In this part of the Loddon, large woody material can be found in abundance.

Stands of trees line the banks and cast patches of dappled shade that cool the river in the hot summer months and create lots of small refuges that fish could hide among to escape from predation.

Unfortunately, from evidence collected from the Loddon at Twyford, the site was not as idyllic as it now seems, before we created a backwater as part of our Charvil Meadows project, to improve this section of river.

To create a baseline of what was in the river, the South East Rivers Trust carried out an electro-fishing survey with the help of Martin Moore and the Loddon Fisheries and Conservation Consultative (LFCC).

Along a short stretch of river that should support hundreds of fish, only 37 individual fish were caught – 13 of those were minnow and bullhead. The same survey recorded few mature fish and only a small number of chub and dace, which are normally indicators of a healthy river.

Martin Moore and co conducting an electrofishing survey for a baseline in the nearby Loddon before the construction of a backwater

A backwater to reverse wildlife losses

The Loddon at Charvil Meadows is downstream of the first major barrier to fish migration, meaning that the depleted fish population was not caused by access to the stretch being blocked. It was a worryingly clear demonstration that our rivers might not be in as good as condition as they appear.

The presence of the occasional braided channel, gravel bar and decent riffle habitat should support somewhat healthy fish populations. However, large scale historic changes have affected the river in some of the most fundamental ways.

Regular dredging over hundreds of years has almost completely disconnected the river from its floodplain for much of the year. This means that the river has become almost continuously a single or braided channel along its length. The incised channel drains the land around it and reduces the habitat suitability for freshwater macro-invertebrates in most areas outside of the main channel – invertebrates on which fish are heavily reliant for food.

There is also chronic pollution from a range of substances including pesticides, oils, heavy metals and sewage. All of these can suppress the populations of fish within a river until a large acute pollution event causes a mass die-off of fish.

Reversing these losses will take a lot of concerted effort across the entire landscape, which can start with small-scale interventions to return some of the missing habitat. That is what we have done on the River Loddon at Charvil Meadows.

Charvil Meadows before a backwater was created

Creating a refuge against pollution

The backwater was designed so that during a large pollution event the water within the backwater will remain largely clean, providing a safe haven for all manners of wildlife to take sanctuary until the pollution has passed.

Additionally, the still water habitat that has been created will allow fish to take shelter during floods and prevent them from being ‘washed out’ of the system.

This shallow pool will provide ideal habitat for fish fry to develop in during the warmer months. Large pieces of wood have been dug into the banks to provide additional shelter and habitat.

The dark grey clay indicates the layer of soil where ground water is permanently present

Planting bulbs and installing woody debris

During the course of the project, we excavated about 1,000 tonnes with the help of R Collards and graded the banks to create a small marginal shelf under the water in such a way that native aquatic plants will blossom and burst into life in spring.

We sowed a native mix of aquatic and semi-aquatic seeds around the site to help native plant species thrive and lifted woody materials into the water to form micro-habitats for fish and invertebrates.

The project was designed and delivered by the South East Rivers Trust, with help from the digger driver from Kenward Groundworks.

Large pieces of wood were secured in the backwater to form great micro-habitats for fish and invertebrates

Help and funding

The creation of this backwater was funded by a generous grant from the Loddon Fisheries and Conservation Consultative as part of an Enforcement Undertaking by Thames Water for pollution event(s) and supported by the landowner Wokingham Borough Council and the Environment Agency. We are very grateful to Martin Moore for volunteering his time and services with the electrofishing survey.

We received permission from a landowner local to Twyford village and their tenant farmer for access through their field, without which this project would not have been successful.

The initial project work featured in the media, with interviews given to Radio Berkshire Radio 4’s Farming Today plus filming by BBC South East.

Charvil Meadow after construction of the backwater

Return visits during Loddon Rivers Week

Since the backwater was completed in 2020, we have returned during two subsequent Loddon Rivers Weeks, the annual celebration of the wider river network, held in early autumn.

During the first, with the help of volunteers from LFCC, we installed nearly 500 native plants to stabilise the banks of the backwater. We also put in two tonnes of gravel to provide potential spawning habitat, and LFCC carried out a fish survey, finding more than 100 individual fish.

During a site visit in Loddon Rivers Week 2022, it was evident that the whole area was settling down, with a diverse plant life becoming established on the banks. Unfortunately, this was accompanied by significant numbers of the non-native invasive species Himalayan Balsam, which destabilises and overshadows river banks, preventing growth of more native plants.

The backwater itself had near 100% coverage of what appeared to be Great Duckweed, the UK’s largest species. This was probably the result of the summer’s lengthy period of high temperatures causing low flows.

Nevertheless, a sweep of a net through part of the backwater produced a diverse catch of nearly 100 small fish, including 39 perch, 19 minnow, plus chub, stickleback and perch, showing that the back.

The Charvil Meadows backwater when we returned in Loddon Rivers Week in September 2022

Thanks to our supporters