Overflow history upstream of Nidd at the Lido, Knaresborough
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 | 47 | 1,534 | 10,313 | 1,653 |
| 2022 | 47 | 1,293 | 6,952 | 882 |
| 2023 | 52 | 2,090 | 16,849 | 2,583 |
| 2024 | 51 | 1,863 | 13,867 | 2,461 |
| 2025 | 51 | 1,239 | 8,519 | 1,396 |
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 52, 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 |
|---|---|---|---|---|---|---|---|---|---|
| Spital Croft storm overflow Spital Croft/CSO · YWS00279 | Yorkshire Water | 1.7 | under 1 | 92% | 24 | 26 | 21 | 42 | 99% |
| Cragg Top storm overflow Cragg TOP/CSO · YWS00277 | Yorkshire Water | 1.7 | 1 | 92% | 15 | 13 | 11 | 106 | 96% |
| Abbey Road storm overflow 2 Abbey Road/NO 2 CSO · YWS00231 | Yorkshire Water | 1.8 | 1 | 91% | 15 | 20 | 19 | 49 | 81% |
| Waterside 48 storm overflow Waterside 48/CSO · YWS00274 | Yorkshire Water | 2.4 | 1 | 89% | 55 | 43 | 24 | 43 | 89% |
| Waterside 47 storm overflow Waterside 47/CSO · YWS00273 | Yorkshire Water | 2.5 | 1 | 89% | 24 | 23 | 28 | 60 | 92% |
| Boroughbridge Road storm overflow Boroughbridge Road/CSO · YWS00276 | Yorkshire Water | 2.9 | 2 | 87% | 10 | 10 | 5 | 2 | 98% |
| Waterside 49 storm overflow Waterside 49/CSO · YWS00275 | Yorkshire Water | 3.0 | 2 | 87% | 12 | 17 | 16 | 14 | 98% |
| Killinghall storm overflow 2 Killinghall/NO 2 CSO · YWS00248 | Yorkshire Water | 12.8 | 7 | 44% | 24 | 19 | 11 | 27 | 100% |
| The Granary storm overflow THE Granary/CSO · YWS00114 | Yorkshire Water | 15.9 | 9 | 37% | 85 | 82 | 41 | 320 | 93% |
| Village Green storm overflow Village Green/CSO · YWS01067 | Yorkshire Water | 15.9 | 9 | 37% | 0 | 0 | 0 | 0 | 100% |
| Birstwith storm overflow 2 Birstwith/NO 2 CSO · YWS00224 | Yorkshire Water | 17.7 | 10 | 32% | 51 | 20 | 5 | 14 | 100% |
| Darley sewage works overflow Darley/STW · YWS00249 | Yorkshire Water | 21.7 | 12 | 26% | 131 | 146 | 97 | 1,490 | 100% |
| Darley sewage works overflow Darley/STW · YWS00250 | Yorkshire Water | 21.7 | 12 | 26% | 40 | 86 | 33 | 151 | 100% |
| Dacre Banks storm overflow Dacre Banks/CSO · YWS01155 | Yorkshire Water | 24.5 | 14 | 22% | 137 | 118 | 48 | 281 | 100% |
| Summerbridge storm overflow Summerbridge/CSO · YWS00677 | Yorkshire Water | 25.2 | 14 | 21% | 62 | 55 | 55 | 473 | 100% |
| Pateley Bridge sewage works overflow Pateley Bridge/STW · YWS00225 | Yorkshire Water | 28.8 | 16 | 16% | 129 | 132 | 79 | 1,213 | 100% |
| Pateley Bridge sewage works overflow Pateley Bridge/STW · YWS00226 | Yorkshire Water | 28.9 | 16 | 16% | 0 | 7 | 15 | 113 | 100% |
| Glasshouses Bridge storm overflow Glasshouses Bridge/CSO · YWS00716 | Yorkshire Water | 29.5 | 16 | 15% | 70 | 28 | 18 | 47 | 100% |
| Nidd Walk storm overflow Nidd Walk/CSO · YWS00863 | Yorkshire Water | 30.7 | 17 | 14% | 78 | 58 | 38 | 248 | 100% |
| Show Ground storm overflow Show Ground/CSO · YWS00715 | Yorkshire Water | 31.5 | 18 | 13% | 28 | 22 | 8 | 39 | 100% |
| Harrogate North sewage works storm tank overflow Harrogate North/STW/3Xdwf Overflow · YWS01039 | Yorkshire Water | 9.9 | 6 | 7% | 96 | 69 | 56 | 504 | 100% |
| Harrogate North sewage works overflow Harrogate North/STW/6Xdwf Overflow · YWS01040 | Yorkshire Water | 9.9 | 6 | 7% | 61 | 53 | 37 | 108 | 100% |
| Ripley storm overflow 2 Ripley/NO 2 CSO · YWS00247 | Yorkshire Water | 12.9 | 7 | 5% | 2 | 11 | 3 | 2 | 100% |
| Skipton Road 33 storm overflow Skipton Road 33/CSO · YWS00253 | Yorkshire Water | 12.2 | 7 | 5% | 1 | 6 | – | – | 0% |
| Skipton Road 109 storm overflow Skipton Road 109/CSO · YWS00255 | Yorkshire Water | 12.2 | 7 | 5% | 9 | 11 | 6 | 2 | 100% |
| Unity Grove storm overflow Unity Grove/CSO · YWS00252 | Yorkshire Water | 12.2 | 7 | 5% | 5 | 8 | 5 | 2 | 86% |
| Skipton Road 179 storm overflow Skipton Road 179/CSO · YWS00251 | Yorkshire Water | 12.2 | 7 | 5% | 3 | 7 | 1 | 0 | 95% |
| Skipton Road 83 storm overflow Skipton Road 83/CSO · YWS00254 | Yorkshire Water | 12.2 | 7 | 5% | 1 | 1 | 0 | 0 | 100% |
| Jenny Plain Bridge storm overflow Jenny Plain Bridge/CSO · YWS00256 | Yorkshire Water | 12.6 | 7 | 5% | 26 | 21 | 22 | 32 | 79% |
| Oakdale Avenue storm overflow Oakdale Avenue/CSO · YWS01159 | Yorkshire Water | 12.9 | 7 | 5% | 30 | 24 | 18 | 19 | 100% |
| Oakdale Harrogate storm overflow Oakdale Harrogate/CSO · YWS00979 | Yorkshire Water | 12.9 | 7 | 5% | 7 | 6 | 3 | 4 | 100% |
| Strawberry Dale storm overflow Strawberry Dale/CSO · YWS00269 | Yorkshire Water | 13.0 | 7 | 4% | 61 | 43 | 26 | 24 | 100% |
| Kings Road storm overflow Kings Road/CSO · YWS00263 | Yorkshire Water | 13.0 | 7 | 4% | 2 | 3 | 1 | 1 | 100% |
| Hotel Majestic storm overflow Hotel Majestic/CSO · YWS00260 | Yorkshire Water | 13.0 | 7 | 4% | 2 | 31 | 27 | 62 | 100% |
| Chudleigh Road storm overflow Chudleigh Road/CSO · YWS00265 | Yorkshire Water | 13.0 | 7 | 4% | 5 | 13 | 2 | 1 | 95% |
| Hyde Park Road storm overflow Hyde Park Road/CSO · YWS00270 | Yorkshire Water | 13.0 | 7 | 4% | 3 | 15 | 27 | 22 | 99% |
| St Marys Walk 112 storm overflow ST Marys Walk 112/CSO · YWS00259 | Yorkshire Water | 13.2 | 7 | 3% | 114 | 86 | 49 | 108 | 100% |
| Albert Street storm overflow Albert Street/CSO · YWS00268 | Yorkshire Water | 13.2 | 7 | 3% | 49 | 41 | 34 | 44 | 100% |
| St Marys Walk 29 storm overflow ST Marys Walk 29/CSO · YWS00258 | Yorkshire Water | 13.2 | 7 | 3% | 80 | 40 | 30 | 42 | 98% |
| Cambridge Street storm overflow Cambridge Street/CSO · YWS00266 | Yorkshire Water | 13.1 | 7 | 3% | 38 | 24 | 8 | 4 | 95% |
| Cold Bath Road storm overflow Cold Bath Road/CSO · YWS00262 | Yorkshire Water | 13.2 | 7 | 3% | 1 | 1 | 0 | 0 | 91% |
| Montpellier RD27 storm overflow Montpellier RD27/CSO · YWS00264 | Yorkshire Water | 13.2 | 7 | 3% | 0 | – | 12 | 14 | 68% |
| West Park storm overflow West Park/CSO · YWS00267 | Yorkshire Water | 13.2 | 7 | 3% | 2 | 6 | 2 | 0 | 100% |
| St Marys Walk 30 storm overflow ST Marys Walk 30/CSO · YWS00257 | Yorkshire Water | 13.2 | 7 | 3% | 12 | 20 | 17 | 18 | 100% |
| St Marys Walk 7 storm overflow ST Marys Walk 7/CSO · YWS00261 | Yorkshire Water | 13.5 | 8 | 3% | 15 | 17 | 12 | 15 | 100% |
| Shaw Mills sewage works overflow Shaw Mills/STW · YWS00227 | Yorkshire Water | 17.6 | 10 | 3% | 131 | 105 | 87 | 1,415 | 100% |
| Shaw Mills sewage works overflow Shaw Mills/STW · YWS00228 | Yorkshire Water | 17.6 | 10 | 3% | 122 | 74 | 39 | 180 | 100% |
| Darley Head storm overflow Darley Head/CSO · YWS00306 | Yorkshire Water | 24.0 | 13 | 2% | 42 | 35 | 23 | 138 | 100% |
| Hirst Lane storm overflow Hirst Lane/CSO · YWS00223 | Yorkshire Water | 17.5 | 10 | 1% | 107 | 95 | 65 | 846 | 100% |
| Bilton Lane Beck storm overflow Bilton Lane Beck/CSO · YWS00222 | Yorkshire Water | 9.7 | 5 | 1% | 26 | 32 | 23 | 36 | 92% |
| Hambleton Road storm overflow Hambleton Road/CSO · YWS01035 | Yorkshire Water | 10.3 | 6 | 1% | 1 | 2 | 4 | 5 | 85% |
| Hollins Close storm overflow Hollins Close/CSO · YWS00115 | Yorkshire Water | 15.7 | 9 | 1% | 46 | 38 | 28 | 137 | 91% |
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.