Overflow history upstream of Wharfe at Cromwheel, Ilkley
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 reach |
|---|---|---|---|---|
| 2021 | 15 | 604 | 1,743 | 715 |
| 2022 | 15 | 566 | 2,102 | 881 |
| 2023 | 15 | 693 | 3,392 | 1,557 |
| 2024 | 15 | 569 | 2,554 | 856 |
| 2025 | 15 | 450 | 1,721 | 477 |
Reach is the share of a spill's bacteria SwimSignal's model expects to arrive here, after die-off on the way and dilution by the river. 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 reach is worked out.
The overflows, by reach
All 15, the one whose spills matter most here first. Hours away is how long sewage takes to arrive at the model's river speed.
| Overflow and id | Company | km upstream | Hours away | Reach | Spills 2023 | Spills 2024 | Spills 2025 | Spill hours 2025 | Monitor uptime 2025 |
|---|---|---|---|---|---|---|---|---|---|
| Rivadale View storm overflow Rivadale View/CSO · YWS00674 | Yorkshire Water | 0.5 | under 1 | 98% | 65 | 40 | 20 | 48 | 100% |
| Addingham sewage works overflow Addingham/NO 1 SPS/Preliminary Treatment-STW/6Xdwf Overflow · YWS00145 | Yorkshire Water | 4.1 | 2 | 80% | 100 | 23 | 28 | 61 | 100% |
| Addingham sewage works storm tank overflow Addingham/NO 1 SPS/Preliminary Treatment-STW/3Xdwf Overflow · YWS00144 | Yorkshire Water | 4.1 | 2 | 80% | 94 | 66 | 41 | 371 | 100% |
| Bolton Bridge storm overflow Bolton Bridge/CSO · YWS00828 | Yorkshire Water | 9.2 | 5 | 56% | 20 | 10 | 5 | 24 | 98% |
| Burnsall Car Pk storm overflow Burnsall CAR PK/CSO · YWS00177 | Yorkshire Water | 21.8 | 12 | 21% | 49 | 35 | 27 | 136 | 100% |
| Hebden sewage works overflow Hebden/STW · YWS00190 | Yorkshire Water | 23.4 | 13 | 19% | 29 | 50 | 2 | 2 | 100% |
| Grassington sewage works overflow Grassington/STW · YWS00185 | Yorkshire Water | 25.7 | 14 | 16% | 67 | 36 | 29 | 55 | 100% |
| Linton storm overflow Linton/CSO · YWS01311 | Yorkshire Water | 26.4 | 15 | 15% | 52 | 41 | 19 | 72 | 97% |
| Kettlewell sewage works overflow Kettlewell/STW · YWS00187 | Yorkshire Water | 37.4 | 21 | 4% | 81 | 77 | 70 | 99 | 100% |
| Kettlewell sewage works overflow Kettlewell/STW · YWS00186 | Yorkshire Water | 37.3 | 21 | 4% | 29 | 20 | 20 | 63 | 100% |
| Beamsley sewage works overflow Beamsley/STW · YWS01340 | Yorkshire Water | 8.6 | 5 | 4% | 77 | 104 | 120 | 118 | 100% |
| Bridge Lane storm overflow Bridge Lane/CSO · YWS00179 | Yorkshire Water | 1.2 | under 1 | 2% | 3 | 0 | 0 | 0 | 97% |
| Draughton sewage works overflow Draughton/STW/6Xdwf Overflow · YWS00189 | Yorkshire Water | 12.3 | 7 | 2% | 14 | 47 | 56 | 629 | 100% |
| Draughton Priors Lane storm overflow Draughton Priors Lane/CSO · YWS00188 | Yorkshire Water | 12.3 | 7 | 2% | 4 | 15 | 7 | 28 | 67% |
| Low Mill Lane 179 storm overflow LOW Mill Lane 179/CSO · YWS00191 | Yorkshire Water | 5.0 | 3 | 1% | 9 | 5 | 6 | 17 | 96% |
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.