Raw sewage has been released into the water across Berkshire during and after Storm Ciaran, according to Thames Water.

The water company’s online discharge map showed at least 20 locations across the county where its sewage systems overflowed in the hours before, during and after the storm.

Thames Water says untreated sewage discharges happen when its sewage systems can’t cope with heavy rain. When this happens, it opens storm overflows, releasing the rain and foul water into watercourses.

The water company’s online storm overflow map revealed at least 20 places across Berkshire where its censors recorded overflows during the 48-hour period in which Storm Ciaran hit.

The map reveals that some discharges began even before the storm arrived, on Thursday, November 2 – and that some were still overflowing by the Friday.

The longest overflow was in Chapel Row in West Berkshire. Censors reported Thames Water’s systems had been overflowing into a tributary of the River Bourne sine 4am on Wednesday 1 November – and was still going by 3pm on Friday.

A full list of reported overflow sites is below.

  • Aldermaston 31 hours 30 minutes
  • Arborfield 1 hour
  • Ascot 1 hours 36 minutes
  • Ash Ridge Wokingham 1 hour
  • Beenham 37 hours 45 minutes
  • Bracknell 6 hours 19 minutes
  • Chapel Row 57 hours 16 minutes
  • Coppice Green, Bracknell 30 minutes
  • Easthampstead Park 19 hours 30 minutes
  • Hamstead Marshall 20 hours 30 minutes
  • Hungerford 4 hours 45 minutes
  • Kintbury 35 hours 44 minutes
  • Knights Lane 25 hours 6 minutes
  • Newbury 40 hours 17 minutes
  • Reading 25 hours 15 minutes
  • Sandhurst 25 hours 30 minutes
  • Slough 4 hours 55 minutes
  • Wargrave 5 hours 55 minutes
  • Washwater 57 hours 44 minutes
  • Windsor 2 hours 54 minutes

Thames Water has come under fire for the number of times it has discharged raw sewage into waterways.

The water company discharged sewage water into waterways more than 8,000 times in 2022, 777 of which were storm overflows.

Thames Water says it plans to spend some £1.6 billion on upgrading its infrastructure. But it was also reported earlier this year to be struggling to pay off some £14 billion of debt – and has been criticised for paying millions of pounds in dividends each year to its internal shareholders.

A Thames Water spokesperson said: “We regard all discharges as unacceptable and we have published plans to upgrade over 250 of our sewage treatment works and sewers.

“In Berkshire, we recently upgraded our sewage works in Hungerford, costing £5million and have started a £10million upgrade at our site in East Shefford. We also have a significant upgrade planned for Hampstead Norreys, which is due to complete in 2025.”