This Friday (18 September) marks the start of Earthwatch's biggest WaterBlitz yet, with more than 6,000 people expected to test the UK's waterways over the weekend.

In Richmond, MP Sarah Olney, who is also a member of the Teddington Bluetits, will join local residents and swimmers on Friday morning to test the River Thames at Ham and Kingston riverside, near the YMCA Hawker Centre on Lower Ham Road.

Other MPs, including Cat Smith (Lancaster) and Steve Race (Exeter), will also be involved in testing in their own constituencies.

The testing will measure nitrate and phosphate levels. Selected volunteers in some areas will also collect PFAS (synthetic chemicals which are difficult to break down) samples for analysis by Imperial College London.

The nationwide citizen-science effort comes as the government shapes its new Clean Water Bill, described as a once-in-a-generation reform of the water system.

Claire Williams from Earthwatch told Nub News: "This is our biggest WaterBlitz ever, with more than 6,000 people expected to take part right across the UK."

Antonia Staats from Avaaz – a nonprofit supporting environmental change – added: "The government has called this a once-in-a-generation reform, so it needs to deliver once-in-a-generation ambition."