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Water Level Easing
Easing — down from 0.25 at 04:00, now 0.23
0.23

Marsh Lock

Thames ⚙ Structure
Cherwell Thame and Wye catchment • Harpsden • Wokingham • ID: 2495TH • Level
(22m ago) • 4 readings/hr • 153 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
0.231 mASD
▼ Easing (-1cm/hr)
24h Max
0.257 mASD
24h Min
0.212 mASD
Typical Range
0.11 - 0.40
mASD
Highest Recorded
1.63 mASD
EA official record
1.25 in our data (since Nov 2012)
Current level is 14% 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 · -1 cm over 5h
10 Oct 12:45 ▼ -0.4 cm 0.231 mASD
10 Oct 12:30 ▼ -0.3 cm 0.235 mASD
10 Oct 12:15 ▲ +0.4 cm 0.238 mASD
10 Oct 12:00 ▼ -0.3 cm 0.234 mASD
10 Oct 11:45 ▲ +0.2 cm 0.237 mASD
10 Oct 11:30 ▲ +2 cm 0.235 mASD
10 Oct 11:15 ▼ -3 cm 0.212 mASD
10 Oct 11:00 ▲ +0.7 cm 0.242 mASD
10 Oct 10:45 ▬ steady 0.235 mASD
10 Oct 10:30 ▲ +0.4 cm 0.235 mASD
10 Oct 10:15 ▼ -0.8 cm 0.231 mASD
10 Oct 10:00 ▼ -0.1 cm 0.239 mASD
10 Oct 09:45 ▬ steady 0.240 mASD
10 Oct 09:30 ▬ steady 0.240 mASD
10 Oct 09:15 ▼ -0.1 cm 0.240 mASD
10 Oct 09:00 ▲ +0.1 cm 0.241 mASD
10 Oct 08:45 ▼ -0.1 cm 0.240 mASD
10 Oct 08:30 ▼ -0.1 cm 0.241 mASD
10 Oct 08:00 ▼ -0.1 cm 0.242 mASD
10 Oct 07:45 0.243 mASD

Station Details

  • Monitoring Station: Marsh Lock
  • Watercourse: River Thames
  • Nearest Town: Harpsden
  • County: Wokingham
  • Coordinates: 51°31'44"N 0°53'9"W (51.528776, -0.885703)
  • Open in: Google Maps · Apple Maps (opens your maps app)
  • Date Opened: 1 Jan 1995
  • Status: Active
  • Station Type: River level station (multi-sensor)
Technical details: references, datum, range, flow archive
  • Station Reference: 2495TH
  • RLOI id: 7155 (the EA's check-for-flooding station id)
  • EA Gauge ID: 2495TH-level-stage-i-15_min-mASD
  • Parameter: Level
  • Unit: mASD
  • Typical rise rate: 4 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: Cherwell Thame and Wye
  • Typical Range: 0.111 – 0.400 mASD
  • EA Cross-check: 0.24 mASD (EA at 10 Oct 12:15)

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.

103 storm overflows are traced upstream of this gauge, the nearest 5.8 km away along the river. 0 report discharging now, 101 report not discharging, and for 2 the monitor is offline or has not reported, so their status is not known.

💧
Thames Water · into River Loddon · 5.8 km upstream along the river
12 spills · 121 hours in 2025
Not discharging now · last
💧
Thames Water · into Ashridge Stream · 16.7 km upstream along the river
11 spills · 136 hours in 2025
Not discharging now · last
Placed on the river by its position alone.
💧
Thames Water · into Foudry Brook · 16.7 km upstream along the river
14 spills · 169 hours in 2025
Not discharging now · last
💧
Thames Water · into Barkham Brook · 19.7 km upstream along the river
28 spills · 251 hours in 2025
Not discharging now · last
💧
Thames Water · into Foudry Brook · 26.3 km upstream along the river
40 spills · 689 hours in 2025
Not discharging now · last
💧
Thames Water · into Tributary Of River Blackwater · 27.5 km upstream along the river
27 spills · 325 hours in 2025
Not discharging now · last
💧
Thames Water · into River Thames · 33.1 km upstream along the river
0 spills · 0 hours in 2025
No live feed for this overflow
💧
Thames Water · into Bow Brook · 33.4 km upstream along the river
26 spills · 405 hours in 2025
Not discharging now · last

95 more further upstream, up to 161.1 km away along the river.

3 other overflows within 6 km are downstream of this gauge or on another branch of the river network, so they are not listed.

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...

Flood history near this gauge

Official Environment Agency warnings issued since 2009 for the 12 flood areas linked to this gauge (nearest 2.4 km away).

58flood warnings 200flood alerts

Most recent flood warning: 8 Feb 2026 — River Thames for Shiplake, Lower Shiplake and Wargrave

Year by year
YearWarningsAlerts
2026 1 21
2025 0 14
2024 14 23
2023 0 22
2022 0 1
2021 3 10
2020 4 20
2019 2 9
2018 1 9
2017 0 4
2016 0 14
2015 0 4
2014 19 7
2013 6 19
2012 8 16
2011 0 3
2010 0 2
2009 0 2

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 Harpsden 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

Frequently asked questions

Is the River Thames at Marsh Lock flooding today?

The current level is 0.23m, which is within the typical range of 0.11 to 0.40m. Flooding is unlikely at this level.

Is the river level rising or falling at Marsh Lock?

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

Why is the level slowly falling?

When little or no rain has fallen for a while, a river level gradually drops as the water stored in the ground and soil drains away with nothing to replace it. This is called baseflow recession and is normal in dry spells. A gentle decline like this is expected and is not a sign of a problem — downstream gauges often recede a little faster than headwaters further upstream, and levels recover once rain returns.

What is a normal level for the River Thames at Marsh Lock?

The typical range at this station is 0.11m to 0.40m, based on Environment Agency historical data. Levels above 0.40m 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.

Embed this gauge on your website

Free live river-level widget — ideal for parish councils, angling clubs and local sites. Updates automatically.

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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 →