Studying silt in our rivers
Windermere Sediment Fingerprinting Project
We are excited to introduce a new innovative project taking place around Windermere, designed to deepen our understanding of sediment found in our rivers. This work uses a new method called sediment fingerprinting!
Funded by Catchment Sensitive Farming (CSF) Partnerships programme, the project brings together partners including the EA Chief Scientist Group and Rothamsted Research. South Cumbria Rivers Trust (SCRT) is leading coordination, supported by local representatives from CSF and the National Farmers Union (NFU).
What is sediment and why does it matter?
River sediment refers to any and all solid material transported by a river, including rocks, sand, and soil. It can enter waterways through erosion of channel banks and washing off land, or through human activities like quarrying and forestry. While healthy soils are essential for multiple land uses, including farmland and woodland, eroded soil washed into rivers can exacerbate existing problems, reducing water quality and damaging habitats for macrophytes, invertebrates and even fish spawning grounds. It can also cause practical issues like blocked drainage and eroded footpaths.
Research elsewhere in the UK suggests that in most cases, channel bank erosion is the primary source of river sediment, followed by arable fields and woodland. However, Windermere’s steep slopes and Cumbrian weather could provide different results. The more we know, the better we can work together with local land managers to help keep sediment on the land and out of our freshwaters.
What’s happening in Troutbeck?
We are working together with specialists at Rothamsted Research to use an innovative new technique called ‘sediment fingerprinting’ in Troutbeck, a major tributary of Lake Windermere.
A sediment trap has been installed at the bottom of the catchment to capture material that has been transported down the river during storm events. Volunteers, supported by SCRT are collecting soil samples from a variety of land use types around the valley, including footpaths, farmland, woodland, and fell tops. At the end of the project, the contents of this trap will be analysed and compared against soil collected from the catchment upstream using a new, fast-track method. These samples will indicate which general land types contribute the most sediment into the river and improve our understanding of sediment processes in Troutbeck.
Why Troutbeck?
Although we are interested in sediment transport across the Windermere catchment, this method relies on sediment being transported all the way down a river. Although several other large tributaries flow into Lake Windermere, these have lakes or tarns along their course (e.g., Elterwater, Esthwaite Water, Rydal Tarn, Grasmere), which can skew the results. In contrast, Troutbeck is a relatively straight run through from source to mouth set within a separate valley, making it ideal for this type of research.
Troutbeck is also historically an important salmon spawning river, and sediment inputs to rivers can have a big impact on fish reproduction as they infill spawning gravels and affect oxygen levels in the water.
Next steps
Over the next month, volunteers will be out and about in Troutbeck collecting soil samples from a variety of land uses while the sediment trap is filling up. Afterwards, the soil and sediment samples will be sent to the lab for analysis, with the aim of reporting back in March.