River pollution and warming waters 'dangerous combination' for food & water, Sheffield University study shows

Scientists previously believed rising water temperatures caused by climate change and increased nutrients from pollution could offset the other’s impact on river life.

The new study, conducted by an international group including Sheffield University, the University of Oxford and researchers in France, found freshwater eco-systems are becoming less complex in the warmer, nutrient-rich waters.

Alain Danet, postdoctoral research associate at the University of Sheffield and co-first author of the study, said: “The eyes of the world have been on the Seine River this summer due to the Olympic Games. The challenges faced in Paris demonstrate how important it is to reduce the pollution levels in our rivers and lakes not only for our own health but for the health of our ecosystems.

“Our rivers, lakes, wetlands and underground water supplies store and clean the water that's crucial for people and wildlife. From providing drinking water to providing essential resources to terrestrial and marine ecosystems, healthy freshwater systems are essential.

“These vital ecosystems also protect us from flooding, filter pollution and support countless plants and animals.”

Freshwater ecosystems don’t only maintain water quality, but also allow wildlife to such as eels and salmon to travel vast distances during their life cycles, and act as conveyor belts transporting good nutrients to make soil better for growing our food.

River pollution like this was seen on a global scale in Paris last month when the Olympic Men’s Triathlon was postponed by 24hours due to harmful bacterial levels in the River Seine.

It was previously believed nutrient-rich waters would have a mitigating effect on increasing temperatures, however, the study has shown rivers that are over nutrient could be dangerous for their ecosystems.

Mr Danet explained that whilst a reasonable amount of nutrient in freshwater systems is a good thing, excess nutrient - or nutrient pollution - can lead to harmful algae and other issues in those rivers.

The University of Oxford’s Willem Bonaffe, co-first author of the study, said: “Lake and river creatures are like the kidneys of our planet. They clean water and prevent blooms of poisonous algae and bacteria. Keeping them safe is keeping us safe.

“Climate change and pollution are not isolated problems for our rivers and lakes, as scientists previously believed. Our study has found they interact in complex ways that threaten the balance of life in our waters.

“By reducing greenhouse gas emissions and improving water quality, we can help safeguard the health of our rivers and lakes for future generations.”

The study is said to show the need to reduce pollution levels is even more urgent with the rising impacts of warming from climate change, but that reducing pollution is a “promising path” to mitigate the impacts of climate change.

Yorkshire Water fined over wastewater mismanagement

The findings of the study is released just over a week after Yorkshire Water were fined £47million over it’s management of wastewater treatment and sewage systems.

Ofwat, the water company regulator, handed out a total of £168m in fines to Yorkshire Water, Thames Water and Northumbrian Water.

The firms have come under heavy criticism for releasing too much pollution into our rivers.

Ofwat said the firms "failed to ensure that discharges of untreated wastewater from storm overflows occur only in exceptional circumstances, which has resulted in harm to the environment and their customers".

A Yorkshire Water spokesman said the firm is "disappointed" with the proposed fine and that it had "co-operated fully" with the investigation.

The spokesman pointed to a £180 million plan to reduce sewage discharges before April 2025.

He added: "We will be responding to the notice by 10th September."

Earlier this year, Yorkshire paid a £150,000 penalty to the Environment Agency (EA) for an earlier "unauthorised sewage discharge" into Sheffield's River Don.

The EA said it found sewage at Kirk Bridge Dike in Darnall in April 2020.

Yorkshire Water said the spill was initially caused by a blockage in the sewage network.

A spokesperson for the firm said: "We know incidents of this kind are distressing and when things go wrong, we understand we have a responsibility to make it right and to prevent these things from happening at all."

Sewage spills by water companies into England's rivers and seas more than doubled last year, with 3.6 million hours of spills, according to the Local Democracy Reporting Service.