Overflow history upstream of Bassenthwaite Lake
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 | 15 | 978 | 9,628 | 555 |
| 2022 | 15 | 992 | 7,259 | 478 |
| 2023 | 16 | 1,066 | 9,708 | 630 |
| 2024 | 16 | 925 | 6,912 | 448 |
| 2025 | 16 | 859 | 6,615 | 458 |
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 16, 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 |
|---|---|---|---|---|---|---|---|---|---|
| Keswick sewage works overflow Keswick WwTW · UUP01060 | United Utilities | 5.7 | 18 | 23% | 78 | 78 | 77 | 907 | 99% |
| Thick Riggs storm overflow Thick Riggs CSO · UUP01927 | United Utilities | 6.9 | 20 | 21% | 1 | 0 | 6 | 9 | 100% |
| Rawnsley Hall (AKA Greta Grove) pumping station overflow Rawnsley Hall PS (AKA Greta Grove) · UUP01617 | United Utilities | 8.3 | 22 | 16% | 60 | 56 | 54 | 63 | 100% |
| Penrith Road UUP01536 | United Utilities | 9.9 | 24 | 15% | 6 | 0 | 0 | 0 | 93% |
| Lattrigg Close UUP01117 | United Utilities | 10.4 | 24 | 14% | 5 | 4 | 1 | 0 | 100% |
| Braithwaite Ww pumping station overflow Braithwaite Ww PS · UUP00301 | United Utilities | 5.4 | 20 | 8% | 120 | 114 | 114 | 1,132 | 100% |
| Dubwath sewage works overflow Dubwath WwTW · UUP00657 | United Utilities | 2.6 across the lake | 14 | 8% | 129 | 44 | 12 | 78 | 100% |
| Threlkeld Quarry pumping station overflow Threlkeld Quarry PS · UUP01938 | United Utilities | 16.0 | 32 | 8% | 86 | 78 | 67 | 299 | 98% |
| Bassenthwaite sewage works overflow Bassenthwaite WwTW · UUP00201 | United Utilities | 3.7 | 12 | 6% | 37 | 43 | 58 | 112 | 100% |
| Portinscale pumping station overflow Portinscale SPS · UUP01565 | United Utilities | 6.6 | 22 | 4% | 106 | 111 | 119 | 558 | 100% |
| Embleton sewage works overflow Embleton WwTW · UUP00704 | United Utilities | 5.0 | 18 | 3% | 175 | 158 | 113 | 2,044 | 93% |
| A591/Bus Shelter storm overflow A591/Bus Shelter CSO · UUP00067 | United Utilities | 6.8 | 19 | 3% | 72 | 68 | 72 | 551 | 96% |
| Gategill Beck M/H Near River Flats storm overflow Gategill Beck M/H Near River Flats CSO · UUP00781 | United Utilities | 17.8 | 35 | 2% | 59 | 41 | 53 | 104 | 100% |
| Grange Bridge (200mtrs downstream) UUP00823 | United Utilities | 14.7 | 55 | <1% | 64 | 57 | 53 | 465 | 100% |
| Rosthwaite sewage works overflow Rosthwaite WwTW · UUP01690 | United Utilities | 17.6 | 59 | <1% | 22 | 30 | 21 | 47 | 99% |
| Stonethwaite sewage works overflow Stonethwaite WwTW · UUP01875 | United Utilities | 19.0 | 61 | <1% | 46 | 43 | 39 | 247 | 100% |
A dash: no annual return for that overflow in that year.
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.