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 like Loch Lomond.

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.

BBC Scotland News has used the latest data to create an interactive map which you can use to find out how many spills were recorded in your area, and how long they lasted.

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, none of the new monitors were required to be reported to Sepa.

Scottish Water figures, external show that Glasgow’s 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.

Barcloy Mill Burn in Dumfries and Galloway, which is one of the newly-monitored sites, received the most spills last year, with a total of almost 3,500.

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.

There were 1,270 spills, totalling almost 1,500 hours, last year into West Lothian’s River Almond, which is nearly 28 miles in length.

Local campaigner Ruth Plevin said swimming in the river 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, a member of the River Almond Action Group, 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.

Further along the east coast at Belhaven in East Lothian, surfer Brian Allen has been testing the local water for pollution.

Each week he sends samples to an accredited laboratory to be tested for E.coli and intestinal enterococci.

He says this is the same sampling as done by Sepa, except he tests all year round and 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.

Allen, the regional representative for Surfers Against Sewage, said the results had been providing “really good news” for Belhaven.

He said 86% of the samples were rated as excellent, good or sufficient water quality, which was fine for recreational water users.

“In fact 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.

Allen welcomed Scottish Water’s increase in data publishing and said working collaboratively would help build up a bigger picture of water quality.

He said the figures had showed there were almost daily discharges from the two overflows in the area – but it was not known if there was a link between discharges and water quality.

One of them, at West Barns at Dunbar, recorded 3,300 spills last year – the second highest number in Scotland last year and a newly-monitored site.

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 a number of locations across Scotland where actually we’ve identified links between how our pumps work and how our treatment works work, which have told us where we do get some spills when we shouldn’t have them – and we’ll make the improvements.”

Monitoring in Scotland remains far lower than in England, which has 100% coverage.

Differences in recording means 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