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Citizen scientists make a splash at the 2022 Land Yeo RiverBlitz

(C) Frances Clinch

Data collected by local volunteers have provided a vital snapshot of the nutrient levels in the rivers, streams, ponds, lakes and ditch network across the North Somerset Levels and Moors.

The results collected by citizen scientists will support the work being carried out by Avon Wildlife Trust and the Bristol Avon Rivers Trust (BART) as part of their Wilder Waterway project.

People of all ages from the local area joined the team in May 2022 to take water samples and test the concentration of phosphates and nitrates.

In healthy rivers and streams these nutrients occur naturally in small amounts and are crucial for the growth of aquatic plants and animals. However, too many nutrients entering our watercourses can be a problem for aquatic ecosystems and for people.

Phosphates and nitrates enter watercourses through fertilisers, manure, sewage, waste, urban surface run-off and the use of household products such as washing detergents. They can speed up plant growth and eutrophication and, in extreme cases, cause harmful algal blooms in water bodies.

Eutrophication can have severe impacts on watercourses. Thick mats of algae can form on the surface; scum and foam can appear; and ultimately death and disease of aquatic life such as fish and invertebrates can result from eutrophication. Algal blooms limit the light and oxygen levels in water bodies, reducing availability to aquatic organisms and limiting life within the ecosystem.

Data collected during the Land Yeo RiverBlitz have now been analysed and show that 80% of samples recorded a high level of nitrate (>2mg/L), with low levels of nitrate (<0.5mg/L) recorded in only 3% of samples. Levels greater than 0.5mg/L suggests water quality is likely to impact aquatic wildlife, particularly those sensitive to changes in water quality.

Currently in England, there are no official standards for nitrate levels in freshwater bodies, but high levels of nitrate can cause significant impacts to aquatic ecosystems and are common in watercourses consisting of both urban and agricultural land use.

As well as impacting wildlife, nutrient pollution can have economic impacts due to increasing water treatment costs, commercial and recreational fishing losses, and reduced tourism income.

The most common causes of high nutrient concentrations include:

  • Pesticides and fertilisers are sources of nutrients that can contribute to pollution when they are washed into our rivers from agricultural land, sports grounds, market gardens and even our own back gardens.
  • Agricultural pollution can be caused when livestock have free access to watercourses, or runoff from farm infrastructure or muck heaps flows directly into a watercourse.
  • Water industry continuous discharges from water recycling centres. The single activity with the most widespread impact on rivers is discharges of treated sewage effluent.
  • Combined Sewer Overflows (CSO’s) that are used to provide relief to the sewer system during heavy periods of rain, preventing our homes from flooding. However, when CSO’s kick in, rainwater mixed with raw sewage containing high concentrations of nitrates and phosphates is discharged into our rivers.
  • Despite recent improvements in some of our urban rivers, towns and roads continue to have a negative impact on our rivers.

The data collected during this RiverBlitz gives a picture of the water quality in the area at a particular moment in time, and will be used to identify the key areas which may need restoration and those which need protecting. It’s a helpful indicator which will be shared with partner organisations to guide further investigations.

Frankie Clinch, Nature Reserves and Projects Officer at Avon Wildlife Trust, said:

“We’re so grateful to the local community groups and other individuals who volunteered with us during last year’s RiverBlitz. They turned up in force to do their bit for our local rivers, and we hope their contribution to citizen science inspires even more people to join us for this year’s event.

“We’d also like to thank Wessex Water for funding the project, and of course our project partners at Bristol Avon Rivers Trust.

“If you’d like to register your interest in volunteering for the 2023 project, please email Rozy Gray at BART on rozy@bristolavonriverstrust.org”

The data collected during all Bristol Avon RiverBlitz events since 2016 can be found on the RiverBlitz explorer platform which provides tools for users to compare and explore the datasets.