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0.19

Watford

Colne ⚙ Structure
Colne (Upper) catchment • Watford • Hertfordshire • ID: 2830TH • Level
(32m ago) • 4 readings/hr • 190 views

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Not an emergency service — if in danger call 999. Alerts rely on EA/SEPA/NRW data and are best-efforts. Terms

Current Level
0.188 mASD
▬ Steady
24h Max
0.191 mASD
24h Min
0.180 mASD
Typical Range
0.12 - 0.82
mASD
Highest Recorded
1.69 mASD
EA official record
1.66 in our data (since Aug 1986)
Current level is 11% of this
🚽 Sewage overflows nearby

Recent Water Levels

🌍 floodradar.co.uk
1 day

Flood predictions aren't generated for lock / structure gauges — their levels are driven by gate operation, not by catchment rainfall, so the forecast models would have no skill here.

Recent Readings

Falling · -0.3 cm over 5h
08 Oct 05:15 ▼ -0.1 cm 0.188 mASD
08 Oct 05:00 ▬ steady 0.189 mASD
08 Oct 04:45 ▬ steady 0.189 mASD
08 Oct 04:30 ▬ steady 0.189 mASD
08 Oct 04:00 ▬ steady 0.189 mASD
08 Oct 03:45 ▬ steady 0.189 mASD
08 Oct 03:30 ▬ steady 0.189 mASD
08 Oct 03:15 ▬ steady 0.189 mASD
08 Oct 03:00 ▬ steady 0.189 mASD
08 Oct 02:45 ▼ -0.1 cm 0.189 mASD
08 Oct 02:30 ▬ steady 0.190 mASD
08 Oct 02:15 ▬ steady 0.190 mASD
08 Oct 02:00 ▬ steady 0.190 mASD
08 Oct 01:45 ▼ -0.1 cm 0.190 mASD
08 Oct 01:30 ▲ +0.1 cm 0.191 mASD
08 Oct 01:15 ▬ steady 0.190 mASD
08 Oct 01:00 ▼ -0.1 cm 0.190 mASD
08 Oct 00:45 ▬ steady 0.191 mASD
08 Oct 00:30 ▬ steady 0.191 mASD
08 Oct 00:15 0.191 mASD

Station Details

  • Monitoring Station: Watford
  • Watercourse: River Colne
  • Nearest Town: Watford
  • County: Hertfordshire
  • Coordinates: 51°40'14"N 0°22'49"W (51.670654, -0.380235)
  • Open in: Google Maps · Apple Maps (opens your maps app)
  • Date Opened: 1 Jan 1985
  • Status: Active
  • Station Type: River level station
Technical details: references, datum, range, flow archive
  • Station Reference: 2830TH
  • RLOI id: 7184 (the EA's check-for-flooding station id)
  • EA Gauge ID: 2830TH-level-stage-i-15_min-mASD
  • Parameter: Level
  • Unit: mASD
  • Typical rise rate: 1 cm/hr (p95 sustained over 90 days)
  • Typical data delay: ~22 min (measured reading→publication lag)
  • Tidal: No
  • Lock / structure: ⚙ Yes — lock, weir, sluice or pump
  • Catchment Area: Colne (Upper)
  • Typical Range: 0.120 – 0.819 mASD
  • Drainage Area: 352 km² upstream of this gauge
  • Flow Data: Daily mean flow (m³/s) to 6 Oct (2 days behind — the EA publishes each day's mean a day or two after it ends; unchecked, provisional) via EA Hydrology
  • EA Cross-check: 0.19 mASD (EA at 8 Oct 05:15)
  • Flow Archive: National River Flow Archive ↗

Geographic coordinates may reflect the access point for the gauge, and not the precise location in the watercourse that it is taking readings from.

Nearby Stations

Gauges connected to this river, and others nearby. A distance “by river” follows the river on the map; any other is in a straight line.

Connected upstream

Connected downstream

Same river system, separate branch

Nearby

Distances by river: OS Open Rivers. Contains OS data © Crown copyright and database rights 2026.

💧 Storm overflows upstream of this gauge

Storm overflows whose water reaches this gauge on the mapped river network, nearest first by distance along the river. The status is each water company's monitor: it says whether an overflow is discharging, not how much or what it contains.

1 storm overflow is traced upstream of this gauge, the nearest 23.0 km away along the river. 0 report discharging now, 1 reports not discharging.

💧
Thames Water · into Potters Bar Brook · 23.0 km upstream along the river
9 spills · 25 hours in 2025
Not discharging now · last

Nearby, connection not known

Within 6 km in a straight line, but the river map cannot say whether their water passes this gauge.

💧
Thames Water · into Colne Brook · 3.3 km away in a straight line · its watercourse is not on the river map
0 spills · 0 hours in 2025
Not discharging now

These are the water companies' monitor statuses; a spill does not by itself explain a change in the gauge level. River connections and distances are traced on OS Open Rivers (edition 2026-04), which leaves out many small channels. Explore the sewage map →

Contains OS data © Crown copyright and database rights 2026.

Rainfall & Weather

Loading rainfall and weather data...

How often this river runs high

In a typical year this gauge reaches its typical high of 0.82 m on about 1 day. This year so far: 0 days.

2026 0 days so far
2025 1 day
2024 5 days
2023 1 day
2022 0 days
2021 4 days
2020 0 days
2019 0 days
2018 0 days
2017 0 days

Counted from each day's highest reading. Days with missing or implausible readings are left out.

Flood history near this gauge

Official Environment Agency warnings issued since 2009 for the 12 flood areas linked to this gauge (nearest 1.7 km away).

11flood warnings 152flood alerts

Most recent flood warning: 19 Jul 2025 — Radlett and Borehamwood Brooks at Borehamwood

Year by year
YearWarningsAlerts
2026 0 13
2025 1 8
2024 0 28
2023 0 12
2022 0 5
2021 3 15
2020 0 12
2019 0 6
2018 0 4
2017 0 6
2016 0 8
2015 0 6
2014 5 9
2013 0 7
2012 0 8
2011 0 1
2010 0 1
2009 2 3

Warnings apply to a whole flood area, not necessarily this exact spot. Years before 2006 aren't covered by the EA's historic record. See also the Watford flood history.

Flood areas linked to this gauge

Flood warnings and alerts are issued for whole areas. These are the 12 areas linked to this gauge, nearest first.

Show 4 more

Catchment Character

🌊 Mixed response A balance of quick runoff and slower groundwater baseflow.

Your catchment is all the land that drains rainfall into the river above this gauge. Its character — how steep, wet, wooded, urban or chalky that land is — decides how fast rain here turns into a rising river. A steep, bare or clay catchment is “flashy” (rises and falls quickly, floods easily); a flat, chalk or well-wooded one is slow and steady. The tiles below put numbers to that; the flow-duration curve reads left-to-right from the river’s typical high flows (Q5) down to its low flows (Q95) — a steep curve means a flashy river.

The physical character of the land that drains to this gauge, and how it shapes its flood response — from the National River Flow Archive (UKCEH).

Baseflow Index
0.57
mixed response
Avg Annual Rainfall
707 mm/yr
1991–2020 · +2% since 1941–70
Urban Extent
12%
partly urbanised
Highest Daily Mean Flow
27.10 m³/s
30 Oct 2000 · daily mean, not the instantaneous peak
Flow-Duration Curve
mean 0.8512.500.5780.1595% (high)% of days exceeded95% (low)
Daily flow (m³/s) exceeded each % of the time — a steep curve is flashy, a flat one is steady. Q5 high · Q50 median · Q95 low.
Land Cover (2023)
Woodland 9%Grassland 36%Arable 31%Urban 22%Other 1%
Arable 40% → 31% since 1990

Flow affected by: groundwater abstraction, effluent returns, industrial / agricultural abstraction.

Photos

Gauging-station photographs from the National River Flow Archive (UKCEH).

Photos © NRFA / UKCEH & the measuring authority — shown at web resolution. Full gallery on the NRFA ↗

About this gauge

The gauging station is located in the upper River Colne catchment.

More detail

The catchment

A largely pervious (Chalk) catchment with extensive Drift cover. Rural headwaters; considerable urban development in the valley. Extensive gravel workings. catchment difficult to delineate.

The station

Compound Crump Weir with substantial fall d/s (but backwater effects noted during the 2000 and 2003 floods). Superseded (in 1991) a compound thin-plate weir (9.0m broad - often drowned and bypassed).

Flow regime

Flows over the new weir include those for the Bucknall's Brook. Effluent (Blackbird's STW) is now a major component of low flows - can produce abrupt changes in a relatively stable flow regime. Gw catchment that is difficult to delineate; losses occur (to the River Lee) via swallow holes. Runoff also diminished by long term gw abstraction (restoration programme began in 1991).

Descriptions from the National River Flow Archive (UKCEH). NRFA station record ↗

Gauge Details

How this gauging station is built and how long it has measured (NRFA / UKCEH).

Gauge type
Gauging structure
Operating since
1934
Station datum
54.7 mAOD
Flow record
1934–2024 · 90 yrs · 99% complete
Hydrometric area
39
Measured by
Environment Agency

Frequently asked questions

Is the River Colne at Watford flooding today?

The current level is 0.19m, which is within the typical range of 0.12 to 0.82m. Flooding is unlikely at this level.

Is the river level rising or falling at Watford?

Based on the most recent readings, the level is currently steady. The chart above shows the last 12 hours of measurements by default (up to 7 days), updated roughly every 15 minutes.

What is a normal level for the River Colne at Watford?

The typical range at this station is 0.12m to 0.82m, based on Environment Agency historical data. Levels above 0.82m are higher than usually seen and may indicate a flood risk.

How often is this river level data updated?

Readings are supplied by the Environment Agency gauge. FloodRadar checks for updates roughly every 15 minutes; the timestamp above shows how recent the latest available reading is.

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📮 Flood risk by postcode near this gauge

Postcodes within 5 km with properties in the Environment Agency’s rivers-and-sea flood-risk bands:

Check any UK postcode’s flood risk →

🏠 Buying or renting around here? Get the Property Flood-Risk Report for any English postcode — official risk band, recorded floods, warning history, river behaviour and nearby storm overflows. £19 one-off. Learn more →