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Live levels from 2 monitoring stations across Windsor and Maidenhead, updated every 15 minutes.
| Station | Level now | Status | ||
|---|---|---|---|---|
| Horton Mill | 0.12 mASD 1h ago | Low | ||
| 4.3 km by river | ||||
| Hythe End | 0.48 mASD 1h ago | Normal | ||
Stations are listed from source to mouth as the water flows, traced on the river map (OS Open Rivers) and the Environment Agency’s own links between its gauges. A distance “by river” is along the river, and is shown only where the map traces the path.
Contains OS data © Crown copyright and database rights 2026.
Streams and rivers with a gauge whose water joins Colne Brook above one of its gauges, from the source down. Named streams without a gauge that have a page here are listed at the end.
Joins Colne Brook above Horton Mill, its highest gauge, no more than 1.7 km by river above Horton Mill.
| Poylestructure | 1.49 mASD 1h ago | Normal |
Its water passes every gauge on Colne Brook, from Horton Mill down.
Joins Colne Brook above Horton Mill, its highest gauge, no more than 7.2 km by river above Horton Mill.
| London Colney | 1.08 mASD 1h ago | Normal |
| 11.2 km by river | ||
| Watfordstructure | 0.19 mASD 1h ago | Normal |
| 8.4 km by river | ||
| Moor Lane | 7.44 mASD 28h ago | old reading |
| 12.6 km by river | ||
| Denham Colne | 0.14 mASD 1h ago | Normal |
| 880 m by river | ||
| Willowbankstructure | 0.85 mASD 1h ago | Normal |
| 4.1 km by river | ||
| Iver, Clisbys Bridge | 0.36 mASD 1h ago | Normal |
| downstream, distance by river not measured | ||
| Farlows Bridge | 0.39 mASD 1h ago | Normal |
Its water passes every gauge on Colne Brook, from Horton Mill down.
Below Hythe End, its water next reaches Staines, a gauge on River Thames, 2.1 km by river downstream.
Tributaries and where they join are traced on the river map (OS Open Rivers, edition 2026-04) and the Environment Agency’s links between its gauges. The map holds distances between gauges, not the junctions themselves, so a junction is placed between two gauges, and no further up than the tributary’s own lowest gauge. Contains OS data © Crown copyright and database rights 2026.
6 storm overflows are traced upstream of Hythe End, Colne Brook’s lowest gauge on the river map: on Colne Brook itself, on its gauged tributaries, and on smaller streams that join above there.
Official figures for 2025, for the overflows traced upstream of Hythe End: 152 spills over 2,309 hours in total, across all 6.
Each overflow is listed in the stretch above the first gauge its water reaches, from the source down, as on the Gauges tab. A stretch of Colne Brook includes the smaller streams that join it there.
1 other overflow within 3 km of these gauges is placed below Colne Brook’s lowest gauge or on another river, so not listed.
A status is the water company’s own monitor: it says whether an overflow is discharging, never how much or why, and a spill does not by itself explain a change in a river level. A status older than two hours is shown as unknown. Annual figures are the official returns: 12/24-hour spills for England and Wales, overflow events for Scotland (Scottish Water counts differently, so the two cannot be compared). “No data” means the monitor produced no usable data that year, not zero. Overflows are placed on OS Open Rivers (edition 2026-04), which leaves out many small channels: an overflow the map cannot place may still drain here. Contains OS data © Crown copyright and database rights 2026. Sewage in Britain’s rivers →
Live status: © Thames Water storm overflow activity data, licensed under CC BY 4.0. Annual figures for England: Environment Agency Event Duration Monitoring return, © Environment Agency copyright and/or database right, Open Government Licence v3.0.
Dated samples taken by the Environment Agency, not live readings. Results are published days to months after the sample is taken, and many points are sampled only a few times a year, or have not been sampled for years.
47 sampling points on the Colne Brook and the streams that join it above Hythe End, and below it. 21 have a sample from the last 12 months; 25 have any sample banked.
Sampled most recently, anywhere on Colne Brook and its streams:
| Where, from the source down | Sampling points | Newest sample |
|---|---|---|
| River Colne and its streamsjoins Colne Brook above Horton Mill | 32 points22 sampled | 28 Sep 2026 |
| Above Horton Mill | 1 point | 11 Dec 2024 |
| Above Hythe End | 13 points1 sampled | 29 Sep 2026 |
| Below the lowest gauge | 1 point | 29 Sep 2026 |
England's samples only. Each count opens the list of those points, nearest first, with the date of each one’s latest sample (the gauge’s “Upstream of here” list).
FloodRadar does not grade these results: there is no overall score, and official river classifications are a separate dataset. A sample taken downstream of an overflow does not by itself show where anything in it came from. River connections and distances are traced on OS Open Rivers (edition 2026-04), which leaves out many small channels.
Water samples: Environment Agency Water Quality Archive, © Environment Agency and/or database right 2026, Open Government Licence v3.0.
Contains OS data © Crown copyright and database rights 2026.
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