Report reveals evidence of water pollution across the Thames Valley

3rd November 2020

• The Thames Valley catchment has medium to high concentrations of nitrate and phosphate nutrients throughout – key indicators of agricultural and waste water pollution
• High nitrates are common across all water bodies in the Thames catchment, with rivers in agricultural areas having the highest nitrate levels
• Nitrates and phosphates are lowest in ponds. Ponds are well-known to provide healthy habitats and results support this.
• Invertebrate diversity was highest where phosphates were low; although high pollution levels can be found throughout the catchment, there are small habitats with low phosphates across the Thames catchment

Water measurements collected by a record number of volunteers – more than 800 – reveal the state of pollution in local rivers, streams, lakes and ponds across the Thames Valley, in a report published today (Tuesday 3 November) by environmental charity Earthwatch Europe.

Data analysis from Earthwatch’s latest WaterBlitz suggests that most waterbodies in the Thames catchment have medium to high concentrations of nitrate and phosphate nutrients – key indicators of agricultural and waste water pollution.

Nitrates and phosphates are nutrients that enter water bodies through fertilizers, untreated sewage and waste.  In large quantities, these nutrients can cause algae and certain species of plants to grow rapidly, outcompeting other plants for resources such as light, leading to a reduction in biodiversity. Algal blooms and their subsequent decay also reduce the amount of oxygen present in the water, which in extreme cases can lead to the suffocation of fish and invertebrates. In addition, certain types of algal bloom can produce toxins that are harmful to the health of humans, pets and livestock.

Dr Isabel Bishop, Freshwater Research Lead at Earthwatch Europe, explains: “Nutrient pollution is damaging to the environment, the economy and our own health and well-being, so it’s important that we protect our freshwater resources.  Measuring nitrates and phosphates helps us to understand which rivers, streams, lakes or ponds are in danger of pollution, or are already polluted and in need of clean-up efforts.”

A total of 966 measurements were taken across the Thames Valley during the WaterBlitz, which ran from 25 to 28 September.  The measurements provide a snapshot of local water quality which can then be compared to results from previous events to gain a better understanding of local waterbodies and the impact of conservation action in the area.

In addition to monitoring nutrient levels, volunteers from The Riverfly Partnership also recorded aquatic invertebrates.  The presence of animals such as mayfly, shrimp or stoneflies can provide a reliable indication of water quality and biodiversity.  Freshwater shrimp were the most common species found, providing a valuable source of food for fish.

Bishop, adds: “Water pollution has featured heavily in the news recently, and we’d like to say a big thank you to all the volunteers who helped measure water quality at hundreds of locations across the Thames Valley.  A staggering number of you took part in the WaterBlitz this autumn, and your contribution is invaluable in improving understanding of local freshwater quality and issues, and identifying where action is needed most.”  

Earthwatch is working closely with the Environment Agency and UK Centre for Ecology and Hydrology to combine freshwater data across the UK, using citizen science data to complement statutory monitoring.  This openly available data will enable key stakeholders – including water managers and local authorities – to access up-to-date information and make more informed recommendations for the improved management and health of our waterbodies.

Led by Earthwatch and funded by Thames Water, the WaterBlitz has taken place twice a year in the Thames Valley since 2015.  Additional support from the Environment Agency this autumn has helped widen participation to a record-breaking number of volunteers. 

You can find a full copy of this autumn’s WaterBlitz results and to view freshwater data, here.