Combined Sewer Overflow Data Update

27 March 2024
general view of the River Dee

87% of Scotland’s waterbodies are in ‘good’ or better condition - among the best in Europe

showing a newly installed Combined Sewer Overflow or CSO

A newly installed CSO will help reduce flooding on the A8 Greenock

Scottish Water has published its annual data on overflows from the public waste water system in line with our regulatory requirements and our commitment to sharing more information on our performance in this area. 

Our Improving Urban Waters Routemap, published in 2021, set out a range of things Scottish Water aims to improve about how we deliver, report on, and explain our essential waste water handling.  

These are: 

  • To improve water quality  
  • To increase monitoring and reporting to cover all waste water overflows that discharge into the ‘highest priority’ waters 
  • To significantly reduce sewer-related debris in the environment
  • To reduce overflows from the public sewer system

“Our waste water treatment systems handle more than 1 billion litres of waste water every day. They are a vital part of the water cycle in Scotland.”

Simon Parsons
Director for Strategic Customer and Service Planning, Scottish Water
Professor Simon Parsons, Director of Environment, Planning and Assurance for Scottish Water, said: “The quality of Scotland’s water environment remains high, with 87% of water bodies classed as good or better.

"We continue to invest in infrastructure - £500million in addition to the £2bn spent in the last decade – which helps improve it further to meet national targets. 

“Our waste water treatment systems handle more than 1 billion litres of waste water every day and are a vital part of the water cycle in Scotland.
“The routemap we published in 2021 set out a crystal-clear commitment to invest further, monitor performance at more locations and strive to prevent pollution incidents before these happen. We are on track to deliver on those commitments.”
Better visibility of data and an increasing amount of data published for monitored overflows are the first steps in our commitment to better overflow management.
Scottish Water is required by our regulator, SEPA, to report on waste water overflow data in selected assets.  And there are other areas of water where we are not required to report overflows, but we are choosing to, in order to help demonstrate our transparency on this important issue.
‘SEPA reported’ waste water overflow data for 2018-2022 was published on the Scottish Water website on the 30th March 2023. 
The latest reported overflow data for 2023 is being published today (March 27, 2024) and covers a five-year overflow data period.  Again, this information covers what we must report to SEPA, each year.
‘Non-SEPA reported’ overflow data was first published in December 2023 and this is also being updated today to include 2023 data. We intend to increase the number of locations for which we publish information as we deploy new monitors in line with our ambitious commitments.