Longtown Storm Overflow
Storm overflow run by Dwr Cymru Welsh Water, discharging into Unnamed Brook.
"Not discharging" means the company's monitor reports no discharge right now — not that the water is clean. The feed publishes status only; no discharge volume is measured.
Year by year
Dŵr Cymru Welsh Water's annual Event Duration Monitoring return to Natural Resources Wales (12/24-hour spill count), as compiled by The Rivers Trust. 2026 is our own running count, the same way, from the live feed since 28 February (when we began keeping every discharge it reports) — so it can only be lower than the full year. The official figure is published next spring.
"No data" means the monitor was not working or not required to report that year — not zero.
Downstream of this overflow
The next gauge downstream that the river map places is Grosmont Rhosllwyn River Station (Monnow), 19.5 km along the river.
Water-sampling points downstream
The nearest Environment Agency sampling points the river map places below Grosmont Rhosllwyn River Station. Points between this overflow and that gauge cannot be put in order with it on the map, so they are not listed.
- River Monnow, Rockfield Park House
38 km along the river · Last sampled 8 Jun 2026 · 4 months ago - River Wye at Redbrook Railway Bridge
50 km along the river · Last sampled 17 Aug 2026 · 45 days ago
A sample is dated: it is not the river now, and its results are on its own page. A sample taken after a discharge does not show that the discharge caused what was measured. Samples: Environment Agency Water Quality Archive, © Environment Agency and/or database right 2026, Open Government Licence v3.0.
A river gauge measures the level of the river; it does not measure this overflow's discharge, and a spill does not by itself explain a change there. This overflow was placed on the river by its position alone. Traced on OS Open Rivers (edition 2026-04), which leaves out many small channels.
Contains OS data © Crown copyright and database rights 2026.
Discharges we have recorded
29 discharge periods since 20 Jan 2021. 28 of them come from Dwr Cymru Welsh Water's own event-duration-monitoring records (published by the company, Jan 2021 – Dec 2025); the live feed adds anything after that. The official annual count is the figure to quote.
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Sun 22 Feb 2026, 08:155 h 45 min
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Thu 18 Dec 2025, 15:4512 h 45 min
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Tue 9 Dec 2025, 08:301 d 11 h
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Sat 6 Dec 2025, 05:4523 h 45 min
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Fri 14 Nov 2025, 08:302 d 14 h
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Sun 5 Jan 2025, 21:301 d 1 h
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Thu 28 Sep 2023, 11:4530 min
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Sun 25 Jun 2023, 05:0015 min
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Mon 23 Jan 2023, 19:1515 min
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Mon 23 Jan 2023, 16:452 h 0 min
Show 19 earlier
| Started (UK time) | Ended | Discharge time |
|---|---|---|
| 14 Jan 2023, 09:00 | 00:30 | 15 h 30 min |
| 12 Jan 2023, 00:45 | 05:30 | 1 d 4 h |
| 14 Dec 2022, 02:00 | 04:30 | 2 h 15 min |
| 14 Dec 2022, 01:00 | 01:15 | 15 min |
| 12 Dec 2022, 09:45 | 10:00 | 15 min |
| 8 Dec 2022, 14:30 | 15:00 | 30 min |
| 8 Dec 2022, 08:45 | 11:45 | 3 h 0 min |
| 8 Dec 2022, 03:00 | 04:00 | 1 h 0 min |
| 8 Dec 2022, 00:45 | 02:30 | 1 h 30 min |
| 8 Dec 2022, 00:00 | 00:15 | 15 min |
| 12 Mar 2022, 21:45 | 13:45 | 1 d 16 h |
| 11 Mar 2022, 23:45 | 11:00 | 11 h 0 min |
| 20 Feb 2022, 23:00 | 06:30 | 7 h 30 min |
| 20 Jan 2022, 22:45 | 01:15 | 2 h 0 min |
| 31 Oct 2021, 19:45 | 21:00 | 1 h 15 min |
| 31 Oct 2021, 09:30 | 17:30 | 8 h 0 min |
| 20 Feb 2021, 11:30 | 02:30 | 15 h 0 min |
| 30 Jan 2021, 09:15 | 01:45 | 16 h 30 min |
| 20 Jan 2021, 02:15 | 17:45 | 1 d 15 h |
The year figures above use the EA's 12/24-hour counting method, so they are comparable with the official figures; the monitor log's 34 raw blocks were merged into 29 continuous discharge periods (gaps under 15 min joined).
Rain nearby last 30 days
Nearest live rain gauge: Tafalog River Station, 5.1 km away. Brown shading = when this overflow was discharging; ▼ = a discharge start.
Overflow shading is a timing match, not proof of cause — heavy rain and spills share a trigger. Times come from the water company’s event-duration monitor (site status only; no discharge volume is published).
Where it is
Concerned about this overflow?
Report pollution you can see or smell to the regulator straight away; the company handles complaints about the overflow itself.
Live status: © Dŵr Cymru Welsh Water, from its Storm Overflow Map. Spill-event history: © Dŵr Cymru Welsh Water's published EDM start/stop records. Annual figures: The Rivers Trust EDM compilation, © Dŵr Cymru/Welsh Water, Open Government Licence. Times are shown in UK local time. FloodRadar republishes the monitor's status; it does not measure discharges itself.