Bristol Avon

Bristol Avon WaterBlitz

2021 Bristol Avon WaterBlitz data is now live!

This is a tool for viewing the health of the rivers and streams of the Bristol Avon Catchment.

The data has been collected by Citizen Scientists who took water samples of our local rivers, measuring the levels of nutrients in their chosen watercourse. The data collected demonstrates where levels of nutrients are low, medium or high, giving an indication of water quality in the immediate vicinity at that time.

The Project

The Bristol Avon WaterBlitz is an annual citizen science event that gives a snapshot of water quality in the rivers and streams across the catchment. The event is run in partnership with FreshWater Watch, a global programme developed by the environmental NGO, Earthwatch, who coordinate WaterBlitz events around the world.

BART continues to work with partners to improve our rivers for the benefit of people and wildlife, and one of the most significant obstacles to healthy rivers is water quality; in particular the high levels of contaminants impacting our freshwater ecosystems. The Bristol Avon WaterBlitz enables anyone with a passion for their local green and blue environment to contribute to its conservation.

The results from the WaterBlitz project help us target areas and influence future conservation projects. The WaterBlitz results also contribute to a global water quality database which assesses the quality of freshwater ecosystems all over the world. Using this interactive site, you can view all the WaterBlitz results collected by our volunteers.

Our project partner, FreshWater Watch, says:

"WaterBlitzes are a fantastic way to connect communities to their local watery areas. Getting people out and about in nature helps deliver the important messages about protecting our precious ecosystems from the many threats they face. BART will be using the measurements you collect to help inform future work in your area, and to educate on the challenges faced in our local environments."

BART have been running WaterBlitz each year since 2016 and have seen it grow with each event to become a catchment-wide, community-led project. To get involved in our next event, keep an eye on BARTs social media and website

The Issue

Citizen Scientists take water samples throughout the month, measuring the levels of nutrients in their chosen watercourse. The data collected demonstrates where levels of nutrients are low, medium or high, giving an indication of water quality in the immediate vicinity at that time.

In healthy rivers and streams 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 us too.

Nitrates and phosphates are nutrients that 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.

How to Help

What can I do?

Figures released by the Environment Agency in September 2020 showed that under the EU Water Framework Directive (WFD), no English river has achieved good chemical status, suggesting pollution from sewage discharge, chemicals and agriculture are having a huge impact on river quality.

In the United Kingdom around 90% of lowland surface freshwaters like rivers, streams and ponds have ecologically damaging levels of either nitrogen, phosphorus or both.

Stopping this pollution is not easy, because nutrients enter rivers from a number of different sources, including naturally occurring sources, from agricultural land and via wastewater treatment works.

Households can reduce the amount of nutrients that they contribute to their wastewater and help improve conditions for our river wildlife. Good water quality, healthy populations of aquatic insects, and thriving fish communities are what we would like to see for the streams and rivers of the Bristol Avon catchment.

Take a look at the BART website outlining everyday actions you can take to benefit our local rivers and the wildlife that depends on them.

Take part in WaterBlitz

Anyone can be a Citizen Scientist by taking part in the next Bristol Avon WaterBlitz in July 2021. Details of how to get involved can be found on BART's events calendar.

How can I support WaterBlitz?

The Bristol Avon WaterBlitz is a fantastic Citizen Science project that connects people and communities to their local watercourses and enables all people, regardless of age or background, to take an active role in exploring and protecting the local natural environment.

By running WaterBlitzes across the catchment BART have been able to identify areas of both good and poor water quality and investigate in greater deal the sources of pollutants impacting watercourses. We can compare data between years and locations and build a picture of water quality over space and time.

To continue to grow this valuable project, BART require partners who are keen to proactively support engagement in conservation and citizen science projects. If your organisation would like to sponsor a WaterBlitz in the future and actively help to protect and enhance the local natural environment please get in touch:


Is it dangerous for me or my dog to swim in a river with high nutrient pollution?

You should take care before choosing to swim in rivers. While the levels of nitrates or phosphates are not a sufficient measure of whether a river is safe to swim in there may also be other pollutants or harmful bacteria that could cause harm to swimmers or pets. Our waterways suffer from the pressures of human populations and are receivers of Combined Sewer Overflow (CSO) discharges, storm drain outfalls and agricultural runoff so be wary when choosing to swim.

Remember that dogs can impact river health themselves, potentially disturbing wildlife and introducing harmful bacteria or chemicals to a sensitive ecosystem. Recent research has shown how pet flea treatments can harm river wildlife.

How reliable is this tool as an indicator of river health?

The Bristol Avon WaterBlitz captures water quality measurements at a particular moment in time. Measurements can be influenced by a range of factors including changes in weather, temperature, inputs from other connecting waters, the presence of animals or any number of other changeable factors can cause a different measurement to be found at a different time. Therefore, the data is used as an indicator of water quality to guide further investigations for more accurate and consistent measurements.

River health is measured using a combination of techniques and looks at a multitude of factors over a period of time. This is combined to give a health status of each river through the EU's Water Framework Directive.

How are measurement sites assigned to rivers?

By marking the sites where our Citizen Scientists took their measurements on the map, we can allocate them to their closest section of river. The measurements will apply 600 metres upstream of the closest part of the river, and 400 metres downstream. On the map, the segments of the river are coloured based on the nutrient levels recorded at that site. If there are multiple sites along a segment of river then the colouring is based on an average of those values.

Why are some waterways missing from the data?

The locations of the rivers on our map are based on the Ordinance Survey's Open Rivers dataset. This gives us an accurate picture of where the major rivers are in our catchment. However, the dataset does not include gated waterways (e.g. canals), lakes or some smaller streams.

Why are the markers for some measurement sites faded?

These are measurement sites which have not been allocated to a section of river. However, you can still click on them to view their results. To avoid assigning measurement sites to the wrong river, we will only allocate a site if it is within 50 metres of a river. That does not mean that there is not a freshwater site at that location, just that it is not near a river in our dataset. We use all the measurements sites on the map to help us monitor our catchment whether they have been assigned to a river or not.

Why do the assigned parts of the river stop at forks?

When two different water bodies meet it is difficult to know how this will affect the overall nutrient levels. Since we cannot say for sure what the likely levels will be, it is better not to show any data.

This tool looks great, can I set one up for my local area?

This interactive data viewer has been developed for us by Riskaware. If you would like to know more about what Riskaware do, and the products and services they offer please visit their website -


BART     Riskaware

This interactive data viewer has been developed by Riskaware in collaboration with the Bristol Avon Rivers Trust (BART). It has been created to visualise the results collected by the citizen scientists who have been taking part in the Bristol Avon WaterBlitz.

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