Welsh Water has recorded the highest number of sewage pollution incidents in 10 years, new data shows.
The figures, released by Natural Resources Wales (NRW) on Friday, showed the water company was responsible for 155 pollution incidents in 2024 – 23 relating to water supply and 132 to sewerage – an increase of 42% in the past 10 years, it said.
NRW has called on Dwr Cymru Welsh Water to make “urgent and fundamental changes to its operations”, adding it had seen a “huge deterioration” in the performance of the company since 2020.
Welsh Water accepted its performance “is not where it needs to be” and said it was accelerating investment in key areas to reduce pollution incidents.
Despite the data showing a drop in water supply incidents in recent years, sewage incidents have increased from 89 in 2022 to 107 in 2023 and 132 in 2024.
Of the total number of incidents, NRW said Welsh Water was responsible for six serious category one or two incidents – a drop from seven last year.
Five of these were from sewerage assets and were all category two.
NRW analysis over the last 10 years also showed the main source of incidents were from foul sewers (423), storm overflows (168) and water treatment works (166).
Since 2010, Welsh Water has been legally responsible for monitoring its water quality at its treatment plants and submitting its results to NRW.
But in May, it was fined £1.35m for failing to properly monitor water quality at 300 different sites.
Nadia De Longhi, head of regulation and permitting at NRW, said despite “repeated warnings and interventions” Welsh Water had been “unable to reverse this concerning trend”.
“This has left us with no choice but to pursue a number of prosecutions against the company which have recently concluded,” Ms De Longhi added.
“This is not the outcome we want, nor the best outcome for the environment – our priority will always be to bring companies into compliance and prevent environmental damage from happening in the first place.
“Welsh Water must address the root cause of these pollution incidents and take preventative measures before more harm is done to the water environment.”
NRW added it would be increasing its capacity for monitoring and auditing discharges, as well as clamping down on unpermitted storm overflows and introducing tighter criteria for annual performance reporting.
In a statement, a Welsh Water spokesperson said the industry across the UK had seen increases in pollution incidents but acknowledged the concerns raised in the report.
They said the company had improved their processes to meet the challenge, including “better monitoring leading to detecting more short-lived events and better reporting”.
The statement added: “We are accelerating investment in key areas to reduce pollution incidents with a £4bn investment programme that includes £2.5bn on environmental projects.
“While we have made progress, such as increasing the number of incidents we find and self-reporting, we know more needs to be done.
“We remain committed to working constructively with NRW to deliver improvements and will be engaging closely on their new requirements and guidance, including the development of pollution incident reduction plans and further use of smart technology to spot problems in the sewer network before they can cause a pollution.”
