Water Pollution From Farms Will Worsen With Climate Change, Study Says

Agricultural water pollution could become 20 times more problematic for farmers due to climate change, a new study has revealed.

River water quality was analysed during one of the UK’s wettest ever winters which showed a dramatic increase of pollutants washing off from farmland.

The study, conducted by Rothamsted Research, noted that pollutants running off from farms increased substantially during the winter of 2019/2020, with the amount of soil washed off arable fields showing a twenty-fold increase on average.

While such pollution is hazardous to aquatic wildlife, it also threatens the quality of drinking water. The study, which focused on the River Taw in Devon, predicts the weather pattern responsible will be more common in the future.

Rothamsted Research is a world-leading non-profit research centre based in Hertfordshire that focuses on strategic agricultural science. The recent study also highlights a four-fold increase in levels of nitrate, another major aquatic pollutant arising from fertiliser use, during the wet winter.

The sediment lost from grazed grassland areas roughly doubled, with nitrate runoff increasing by about half, according to the findings in the research, published in the Journal of Cleaner Production.

Adie Collins, the Hydrologist Professor who leads Rothamsted’s research in this area, said: “These changes in autumn and winter rainfall are elevating runoff and the water pollution problems arising from modern farming. Sadly, current on-farm mitigation strategies, including those subsidised by agri-environment schemes, aren’t working very well.”

The data for the research was collected by specialist equipment monitoring the water coming from four fields on a farm and three other nearby sites within the upper reaches of the River Taw catchment in Devon, as well as readings from a Met Office station based on the farm.

The River Taw rises in the uplands of Dartmoor, whilst the study sites were in lowland areas, close to Okehampton.

All major inputs and outputs of the site, as well as detailed analyses on soil, air, water and livestock samples, were measured at Rothamsted’s North Wyke site, the world’s ‘most instrumented farm’, which has traditionally been livestock only, although several fields were recently converted to arable to see what would happen in regard to more people turning to plant-based diets.

Millions of measurements of rainfall, flow and water chemistry were frequently collected throughout a four-year period using state-of-the-art sensors. 

Climate modelling for this site suggests winter 19/20 is a good example of what to expect over the coming decades, said Professor Collins. February 2020 was the wettest February on record for the UK, with the winter ranked as the 5th wettest on record since 1862.

Professor Collins added: “Pollution from intensive farming generates environmental damage with resultant costs such as those for drinking water treatment to remove nutrients and sediment.

“Elevated pollution driven by extreme wet-weather increases such problems considerably.”

Tom Townsend, Principal Consultant - Sustainable Business - “The issue of runoff is not a new one but the potential impact on UK farms and waterways highlighted in this study is concerning. It is clear that we are no nearer to solving this problem and the impact of climate change demonstrates the need to treat agricultural runoff as an immediate threat.”