A report by Surfers Against Sewage has estimated the scale of Scotland’s ‘hidden’ sewage problem to be ten times bigger than the overflow figures reported.

The report stated that “approximately 96% of Scotland’s sewage overflows are unreported, meaning that current data only shows a small fraction of the total amount of sewage that is being pumped into Scotland’s waters.”

"From reported data we do have," it said, "we know that untreated sewage has been discharged tens of thousands of times in the past five years, suggesting that the total amount being discharged from the 3,641 sewage overflows across Scotland is likely to be in the hundreds of thousands."

Surfers Against Sewage has called on the Scottish Government to direct Scottish Water to install "event duration monitoring on all overflows and for that data to be freely and easily accessible to the public in real-time".

It is also demanding “progressive sewage reduction targets to end untreated discharges into bathing waters, popular water usage areas and high priority nature sites by 2030”.

Scottish Water operates over 3,600 sewage overflows in Scotland, but last year only 103 of these were required to be monitored.

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The Surfers Against Sewage Water Quality Report 2023 describes the data as "patchy".  Overflows which remain unreported include, it said, “locations such as Sites of Special Scientific Interest, Designated Bathing Waters, and other popular swim and surf spots.

The report also highlighted the work of Surfers Against Sewage reps, including Charlie Allanson-Oddy, at Edinburgh's Portobello beach.

His story shows increasing collaboration between surfers and other water users. Mr Allanson-Oddy is one of the founders of a new community group, The Porty Water Collective, which is doing regular testing for water quality at the outlet of the Figgate burn.

He said: “It’s obvious from walking the beaches, from the number of baby wipes there is a massive sewage-related problem. Something that is ignored by SEPA and Scottish Water. What we know from 2021 water quality testing (part of SAS 2021 Water Quality Report) and now with the  Porty Water Collective’s water quality testing (backed by SAS) – is that there are dangerously high levels of E.coli and chloroforms in the Figgy [Figgate} Burn from combined sewage overflows further up it. Not all the locals know this.”

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The report also draws attention to three overflows which were once reporting throughout the year, but now only do so throughout the bathing waters season.

“Between 2018 and 2020," it says, "when all annual discharges were reported, these three overflows discharged a total of 381 times. Since then, the reporting of these events has become patchier, but this doesn’t mean they aren’t still having significant impacts.”

It notes that other overflows are now labelled as having “no licence requirement for reporting”.

A Scottish Water spokesperson said: “87% of water bodies in Scotland have been classified as good or better status for water quality by SEPA and our continued investment - £2.7bn in the past decade with an additional £500m to improve monitoring and infrastructure - will help meet even higher standards.

"As a public body, we are independently regulated and fully accountable to Ministers. "We remain on track to install 1000 new monitors at discharge locations, with a further 1200 monitors being placed elsewhere as we transform Scotland's waste water system to cope better with climate change and growth.

"Sewer overflows happen to reduce the risk of flooding in homes and consist mainly of run-off from roads and roofs and grey water from household appliances, with less than 1% coming from waste water from toilets. Water quality can also be significantly impacted from other sources including agricultural run-off."

The report was published on the same day that SEPA announced that 98% of bathing waters had continued over the past season to meet “strict environmental standards”. A

Scottish Government spokesperson said: “SEPA’s latest bathing water data to be published today  shows that Scotland now has the highest number of designated Bathing Water sites ever, with the vast majority classified as good or excellent. This reflects the overall good ecological condition of Scotland’s rivers and coastal waters, and demonstrates the benefits of our continued investment in protecting and improving bathing waters across the country.

“We are not complacent and will continue to work closely with SEPA and Scottish Water to monitor and improve water quality, to make sure that as many people as possible are able to enjoy them.

“Scottish Water is committing up to £500m to improve water quality, increase monitoring of the highest priority waters and tackle debris and spills. However, it is important to note that overflows from sewers are wastewater which has been highly diluted by rainwater, and which normally consist of less than 1% toilet waste.”

“We are also launching today (November 21) a public consultation on Water, Wastewater and Drainage which considers how we limit the amount of rainwater in sewers to reduce overflows from sewers.”