Raw sewage and toilet paper on the shore at Arrochar after recent bad weather. Loch Long was once a playground for working-class people from Dumbarton and the Vale of Leven who camped and went swimming there, fished for mackerel and rock cod, and collected shellfish, clabbys dhub, at places like Carrick Castle. It is now considered to be a no-go area for swimming or fishing. Recently, an application for planning permission to site a fish farm in the loch was refused. Villagers who live there have contacted MSP Jackie Baillie MSP to plead for them with the SNP government to improve matters.
By AimeeStanton, Data Journalist, BBC News Scotland, Kevin Keane, Scotland environment, energy and rural affairs correspondent and Democrat editor Bill Heaney,
Updated 13 November 2026
More than 76,000 sewage spills were recorded after new monitoring equipment was installed at waste overflow sites in Scotland, BBC analysis suggests.
The addition of 1,009 sewer monitors in 2024 increased the proportion of the Scottish Water network being monitored from 6% to 30%.
Now the latest figures have revealed tens of thousands of spills which would previously have been unrecorded, including hundreds at beauty spots such as Loch Lomond and the confluence of the Rivers Clyde and Leven at Dumbarton Castle.
Scottish Water said the vast majority of the spills were not harmful to the environment, and that increased monitoring had improved understanding of the sewer network.
But that is hard to believe given the amount of sewage flowing into the Clyde at the sewage plant near Ardoch and the new works, which have just been built, with the construction which is creating a direct outflow from Dalreoch railway station into the Leven at Dumbarton Bridge.
BBC Scotland News has used the latest data to create an interactive map which readers can use to find out how many spills were recorded in your area, and how long they lasted.
Map of every sewage spill in Scotland
Sewage spills happen automatically at overflow sites, which are permitted to release excess water into natural waterways.
They usually consist of a pipe – set much higher than the usual water level – which provides an escape route when the system is deluged.
These overflows act as relief valves to prevent the sewer system from becoming overwhelmed during heavy rainfall and flooding into homes, businesses and streets.
The spills can last anywhere from a few minutes to hours.
Scottish Water currently has over 4,200 overflows across its network. The number of overflows with monitoring rose from 273 to 1,275 in 2024.
More than 100,000 spills totalling to almost 277,000 hours were recorded last year – an average of about 274 a day.
It is difficult to assess how the numbers compare to the previous year’s figures, when 24,000 spills were recorded because of lower coverage.
The sites are all licensed to release untreated or partially-treated waste, but just under 12% of overflows are legally required to report their data to the regulator, the Scottish Environment Protection Agency (SEPA).
SEPA said it has a “risk-based approach” which prioritises areas for monitoring based on population and environmental need.
However, they claim none of the new monitors were required to be reported to SEPA.
Scottish Water figures show that the River Clyde was one of the most impacted waterways in Scotland last year, receiving almost 6,150 spills – or the equivalent of 17 a day.
When adding in the Clyde Estuary, Firth of Clyde and other unnamed tributaries that run into the Clyde’s waterways, this almost doubles to nearly 14,200, or 39 a day.
The Clyde Estuary also recorded the longest duration of spills – more than 25,000 hours – followed by the River Clyde with more than 15,000 hours.
The data suggests that 225 sites recorded no spills and 525 recorded fewer than 10. There may also be errors, which suggest a monitor is active when it is not.
‘It’s what’s not visible’
One local campaigner, Ruth Plevin, said swimming in the River Almond was part of her childhood and that she now wants to protect it for her own grandchildren.
She said any investment in improving the infrastructure of the water system was welcome.
“It’s what’s not visible that is our concern – the microplastics, the pharmaceuticals, the agrichemicals, stuff that you can’t see,” she said.
Plevin said she wants the group’s legacy to be clean, safe water.
“It’s precious, and I think we need to regard it as precious. Value it, look after it and make it safe.
“I want it to be clean – it’s not a lot to ask for, really,” she said.
However, despite the optimistic view of Ms Plevin and people like her, members of the public continue to go “wild swimming” in Loch Lomond and even indulge themselves in portable saunas near iffy stretches of water.
Are spills affecting water quality?
Each week, samples from some rivers are sent to an accredited laboratory to be tested for E.coli and intestinal enterococci.
This is similar to sampling as done by SEPA, and the tests are done year-round, not just during the bathing season.
SEPA monitors bathing water quality at about 80 sites across Scotland between May and September. It also looks out for algae, seaweed and waste.
Surfers Against Sewage says the results have in some cases been providing “really good news” with as much as 86% of the samples rated as excellent, good or sufficient water quality, which was fine for recreational water users.
A spokesperson for the surfers told BBC Scotland that 77% of the results are coming back as excellent — “What we don’t know is whether that picture is being replicated across the rest of Scotland,” he said.
Simon Parsons, director for wastewater at Scottish Water, said most of the time overflows were doing the job they were designed for – draining rainwater out of the sewer system.
“The vast majority of those spills aren’t harmful to the environment because they’re nearly always about rainwater,” he explained.
Scottish Water said 99% of spills were rainwater, surface water, road run-off, “grey” water from households (not human waste), infiltration of groundwater, and trade effluent.
Parsons said the increase in monitoring had improved understanding of the sewer network and helped identify locations requiring improvement.
“We didn’t necessarily know how and when our overflows were operating, so we’ve got a much better picture now than we’ve ever had before.
“We can actually identify those areas where we need to think about investment.
“We’ve got several locations across Scotland where we’ve identified links between how our pumps work and how our treatment works, which have told us where we do get some spills when we shouldn’t have them – and we’ll make the improvements.”
Scottish Water’s Simon Parsons said the monitors help identify problems in the system
Monitoring in Scotland remains far lower than in England, which has 100% coverage.
Differences in recording mean Scotland’s figures are not directly comparable with the rest of the UK.
Scottish Water said its monitoring had now grown to about 50% and that it was aiming to reach 100% over the next five to six years.
Parsons said the cost was relatively small but represented good value in terms of the intelligence they provided.
Additional reporting by Andrew Picken
Top of page: Wild swimmers enjoy themselves in Loch Lomond where sewage spills are still being recorded.