While Wales has better water quality than England, its rivers still face significant pollution challenges, especially in the Cleddau and Pembrokeshire Coastal Rivers catchment, according to new data.

The Great UK WaterBlitz, organised by Earthwatch Europe, saw 7,978 citizen scientists test 4,017 freshwater sites for nitrates and phosphates in April. The study found that 66 per cent of sites across the UK showed unacceptable pollution levels. In Wales, 37% of sites reported unacceptable levels of nutrient pollution, a better result than England’s 74 per cent, but worse than Scotland and Northern Ireland's 30%.

Within Wales, the Cleddau and Pembrokeshire Coastal Rivers catchment was significantly worse than average with 69 per cent of samples showing unacceptable levels of nutrient pollution. At the other end of the scale, the Meirionnydd catchment was the cleanest with no datapoints showing high levels of nutrient pollution. The Llyn and Eryri fared well too, with just 10 per cent of data points showing significant levels of nutrient pollution.

Participants in the Great UK WaterBlitz measured the levels of two polluting nutrients: nitrate and phosphate. Nitrates and phosphates are commonly present in domestic and industrial waste and sewage, as well as in the fertilisers that wash off farmland. High levels of nutrients cause excessive plant and algal growth, high levels of bacteria, and decreased oxygen levels in the water, killing plants and animals. The worse the nutrient pollution gets, the less able the river is to support aquatic life.

Dr Sasha Woods, Director of Science and Policy at Earthwatch Europe emphasised a “clear need for action to address the issues impacting Welsh rivers and protect these vital resources,” adding: “The UK-wide picture is one of rivers suffocating under relentless pollution - sewage, tyre particles, fertilisers - and it’s time to act across the whole of the UK."