Monitoring of combined sewer overflows (CSOs) has increased 14-fold over the past four years, according to data from the Environment Agency (EA), with 100 per cent coverage expected by 2023.
The EA has for the first time publicly released data on the frequency and length of sewage discharges from the 12,092 CSOs that were monitored in 2020. This showed 403,171 spills last year, a rise of 27 per cent compared to 2019, although this was based on just 8,276 CSOs.
The aim is to have all 14,630 overflows in England monitored by the end of 2023.
The Event Duration Monitoring (EDM) data released by the EA today showed the average number of spills per CSO was 33, although there was significant variance between companies. United Utilities reported the highest average across the year – of 59 – while Southern Water had the lowest – at 21.
It also revealed the average duration of each discharge was eight hours. Here Thames was the worst performer with an average time of 12 hours while Northumbrian and Welsh Water were the lowest – both at five hours.
Water companies are obliged to monitor and report EDM to the EA, which has always released this data via freedom of information requests. However, following commitments made by the Storm Overflows Taskforce to increase the transparency and accessibility of the data, it will now be available annually on the government’s website.
A spokesperson for Water UK said: “Water companies are committed to playing their part in reducing any harm from storm overflows.
“As the data shows, we have massively increased monitoring, with the aim of getting 100 per cent of the 14,630 overflows in England monitored by the end of 2023. This data is invaluable and allows investment to be targeted where it’s needed most.
“A total of £1.1 billion is being invested by water companies to improve storm overflows over the next five years as part of a wider £5 billion programme of environmental improvements. In addition, we are playing a leading role in the government taskforce that is looking at long-term alternatives to storm overflows.
“What we all want to see are improvements in the health of our rivers. Storm overflows account for only around 4 per cent of all the reasons for rivers and waterways not achieving good ecological status, so it’s essential to deal with all the other sources of harm, and all sectors involved will need to play a part in addressing this complex challenge together.”
On Monday (29 March) the government confirmed legal duties on water companies to reduce the harm caused by CSOs would be put into law.