Overflow history upstream of River Thames, Lechlade
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 | 17 | 604 | 8,294 | 92 |
| 2022 | 16 | 447 | 5,558 | 66 |
| 2023 | 21 | 1,369 | 22,334 | 252 |
| 2024 | 21 | 1,591 | 26,544 | 317 |
| 2025 | 21 | 805 | 12,730 | 152 |
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 21, 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 |
|---|---|---|---|---|---|---|---|---|---|
| Fairford sewage works overflow Fairford STW · TWL00178 | Thames Water | 8.8 | 5 | 4% | 162 | 202 | 107 | 2,235 | 100% |
| Shrivenham sewage works overflow Shrivenham STW · TWL00368 | Thames Water | 17.4 | 10 | 2% | 81 | 125 | 56 | 946 | 100% |
| Highworth sewage works overflow Highworth STW · TWL00227 | Thames Water | 9.0 | 5 | 2% | 60 | 66 | 27 | 340 | 100% |
| Hannington TWL00130 | Thames Water | 10.1 | 6 | 2% | 21 | 21 | 8 | 14 | 100% |
| Kilda Road (Highworth) pumping station overflow Kilda Road (Highworth) SPS · TWL00249 | Thames Water | 9.4 | 5 | 2% | 0 | 0 | 0 | 0 | 96% |
| Kempsford sewage works overflow Kempsford STW · TWL00246 | Thames Water | 6.0 | 3 | 1% | 8 | 8 | 0 | 0 | 100% |
| Swindon sewage works overflow Swindon STW · TWL00402 | Thames Water | 26.7 | 15 | 1% | 62 | 47 | 23 | 288 | 100% |
| Wanborough sewage works overflow Wanborough STW · TWL00422 | Thames Water | 23.8 | 13 | 1% | 102 | 150 | 68 | 822 | 100% |
| Highworth Eastrop (GWA site) storm overflow Highworth Eastrop CSO (GWA site) · TWL00226 | Thames Water | 10.6 | 6 | 1% | 32 | 29 | 9 | 12 | 90% |
| Blunsdon sewage works overflow Blunsdon STW · TWL00046 | Thames Water | 12.4 | 7 | 1% | 19 | 13 | 9 | 54 | 98% |
| Stanton Fitzwarren pumping station overflow Stanton Fitzwarren SPS · TWL00723 | Thames Water | 14.4 | 8 | 1% | 11 | 20 | 0 | 0 | 100% |
| Ampney St Peter sewage works overflow Ampney St Peter STW · TWL00010 | Thames Water | 25.3 | 14 | 1% | 130 | 147 | 68 | 1,436 | 93% |
| Cricklade sewage works overflow Cricklade STW · TWL00119 | Thames Water | 17.3 | 10 | 0% | 114 | 107 | 59 | 641 | 100% |
| Sevenhampton sewage works overflow Sevenhampton STW · TWL00362 | Thames Water | 17.7 | 10 | 0% | 103 | 135 | 99 | 2,055 | 100% |
| Hatchetts (Cricklade) pumping station overflow Hatchetts (Cricklade) SPS · TWL00600 | Thames Water | 17.3 | 10 | 0% | 31 | 56 | 33 | 378 | 100% |
| Minety Station Road WXW01061 | Wessex Water | 28.5 | 16 | 0% | 80 | 45 | 22 | 171 | 100% |
| Cirencester sewage works overflow Cirencester STW · TWL00102 | Thames Water | 26.4 | 15 | <1% | 165 | 236 | 125 | 2,067 | 100% |
| Hankerton Hankerton Bridge WXW00500 | Wessex Water | 35.3 | 20 | <1% | 78 | 65 | 34 | 549 | 100% |
| Purton sewage works overflow Purton STW · TWL00337 | Thames Water | 23.6 | 13 | <1% | 41 | 53 | 27 | 322 | 100% |
| Chisledon storm tank overflow Chisledon storm tanks · TWL00790 | Thames Water | 30.7 | 17 | <1% | 23 | 18 | 2 | 8 | 100% |
| Upper Minety Flisteridge WXW00433 | Wessex Water | 35.9 | 20 | <1% | 46 | 48 | 29 | 393 | 95% |
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.