Overflow history upstream of Luss Bay, Loch Lomond
The spot's forecast · For event organisers
This page lists the monitored storm overflows upstream of this spot and how often each spilled in each year. It is not a water test, and it does not say whether the water is fit to swim in. It does not include farm runoff, misconnected drains, treated sewage effluent, wildlife or overflows without a monitor. A year's count depends on how long the monitor worked, shown as monitor uptime.
Each year, all overflows upstream
| Year | Overflows with a return | Spills | Spill hours | Spill hours, weighted by model weight |
|---|---|---|---|---|
| 2021 | 0 | 0 | 0 | 0 |
| 2022 | 0 | 0 | 0 | 0 |
| 2023 | 0 | 0 | 0 | 0 |
| 2024 | 0 | 0 | 0 | 0 |
| 2025 | 0 | 0 | 0 | 0 |
Weight is SwimSignal's modelled relative contribution weight for each overflow here, from its assumptions on travel time and die-off on the way and dilution by the river: neither a measured bacterial concentration nor a calibrated chance of contamination. Weighting by it counts an hour of spilling just upstream for far more than one 40 km away. Spills are counted by the Environment Agency's 12/24 method: any discharge in the first 12 hours counts as one spill, then one more for each 24 hours with any discharge. How the weight is worked out.
The overflows, by model weight
All 8, the one whose spills matter most here first. km away is along the river network, through any lake on the way, or across the lake for one that drains into the same lake. Hours away is how long sewage takes to arrive, at the model's river speed, and across a lake at its slower lake speed.
| Overflow and id | Company | km away | Hours away | Weight | Spills 2023 | Spills 2024 | Spills 2025 | Spill hours 2025 | Monitor uptime 2025 |
|---|---|---|---|---|---|---|---|---|---|
| Killearn sewage works overflow Killearn Wwtw CSO · CSO003544 | Scottish Water | 26.1 | 68 | 3% | – | – | – | – | – |
| Killearn sewage works storm tank overflow Killearn Wwtw SSSO And EO · CSO007422 | Scottish Water | 26.1 | 68 | 3% | – | – | – | – | – |
| Gartocharn sewage works overflow Gartocharn Wwtw CSO · CSO007128 | Scottish Water | 12.6 | 49 | 2% | – | – | – | – | – |
| Strathblane, (Old) sewage works storm tank overflow Strathblane Wwtw - (Old) SSSO · CSO007508 | Scottish Water | 32.9 | 77 | 1% | – | – | – | – | – |
| Strathblane, (New) sewage works storm tank overflow Strathblane Wwtw - (New) SSSO · CSO007253 | Scottish Water | 32.9 | 77 | 1% | – | – | – | – | – |
| Fintry, Post PSTs sewage works storm tank overflow Fintry Wwtw - Post PSTs SSSO · CSO007479 | Scottish Water | 42.1 | 90 | 1% | – | – | – | – | – |
| Strathblane sewage works overflow Strathblane Wwtw CSO · CSO004264 | Scottish Water | 32.9 | 77 | 1% | – | – | – | – | – |
| Drymen sewage works overflow Drymen Wwtw CSO · CSO003225 | Scottish Water | 18.4 | 57 | 1% | – | – | – | – | – |
A dash: no annual return for that overflow in that year.
How long their spills lasted, 2024 and 2025
History: 2024 and 2025.
None of the 8 overflows upstream has a spill in these 2024-25 records: none was recorded, or there is no record. That is not the same as no spills: the annual returns above give each year's count.
Environment Agency, storm overflow EDM start/stop data 2024 and 2025, Open Government Licence v3.0. How to read these, and how long spills already running went on, company by company: Spill durations.
Sources and credits
Storm overflow annual returns: © Environment Agency copyright and/or database right 2025, Open Government Licence v3.0. Overflow positions: the water companies via the National Storm Overflow Hub, CC BY 4.0. River network: contains OS data © Crown copyright and database right 2026 (OS Open Rivers). Traced and weighted by SwimSignal (swimsignal.co.uk), whose method is at swimsignal.co.uk/methods.html. All credits and licences.