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⤴Unusual rise — FloodRadar+Top 1% rise rate for this gauge.
Height for "Above a height"
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You'll be notified when this gauge is rising more than 0.10 m/hr — a sign of rapidly increasing water levels.
You'll be notified when a new storm-overflow (sewage) discharge starts within ~3 km of this gauge, based on the water companies' near-real-time feeds.
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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
0.709 mASD
▲ Rising (+2cm/hr)
24h Max
0.709 mASD
24h Min
0.622 mASD
Typical Range
0.36 - 1.60
mASD
Highest Recorded
1.94 mASD
EA official record
A 2.30 reading (28 Mar 2025) sits in our unverified raw history and is not treated as the record
Current level is 37% of this
Current Flow
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🚽Sewage overflows nearby
Recent Water Levels
🌍 floodradar.co.uk
1 day
EA forecast (official)
Prediction V2
Prediction Eris
Nimbus beta
Experimental model fusing soil moisture, river flow, groundwater and catchment
character. The shaded band is its 10–90% range, widened so that about 80% of recent outcomes fall inside it.
Under evaluation — not yet promoted, so treat as a second opinion.
River Flow
90 days
Daily mean discharge (m³/s) with the daily min–max band, from the EA Hydrology API. Flow is the volume of water passing the gauge — often a more direct flood signal than level.
Flow Data: Daily mean flow (m³/s) to 11 May (151 days behind — the EA publishes each day's mean a day or two after it ends; unchecked, provisional)via EA Hydrology
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.
3 storm overflows are traced upstream of this gauge, the nearest 2.5 km away along the river. 0 report discharging now, 3 report not discharging.
Thames Water · into N/A · 3.7 km away in a straight line · no mapped watercourse close enough to be sure
0 spills · 0 hours in 2025
Not discharging now · last
1 other overflow within 6 km is downstream of this gauge or on another branch of the river network, so it is 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 →
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 Mytchett flood history.
Flood areas linked to this gauge
Flood warnings and alerts are issued for whole areas. These are the 10 areas linked to this gauge, nearest first.
🌊 Urban & flashyHeavily built-up — rain runs off hard surfaces fast, so levels can spike within hours of heavy rain.
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
0.65
mixed response
Avg Annual Rainfall
772 mm/yr
1991–2020 · +8% since 1941–70
Urban Extent
23%
heavily urbanised
Highest Daily Mean Flow
84.95 m³/s
19 May 2022 · daily mean, not the instantaneous peak
Flow-Duration Curve
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.
Side-look Acoustic Doppler Current Profiler (ADCP) gauge located on the River Blackwater at Farnborough.
More detail
The catchment
Tertiary geology - mainly Bagshot Beds with London Clay in the headwaters and alluvium in the valley. Substantial and expanding urban development including Farnborough and Aldershot but large rural tracts remain; significant areas of heathland and woodland.
The station
Currently side-look ADCP. Side-look US installed in February 2009. This replaced the decommissioned EM. The EM had been installed as part of a R&D project into flow within two stage channels.
How it measures flow
Calibration to be completed. Gaugings indicate that EM flows are overestimated in the low and medium range.
Flow regime
Flows managed by STW, supplemented in summer. Siltation occurs.
The flow record
September 1997 and 1998 flows particularly suspect but all flows should be treated with caution.
Timing, not cause. Gauges can move together simply because the same rain fell on both.
Frequently asked questions
Is the River Blackwater at Farnborough flooding today?
The current level is 0.71m, which is within the typical range of 0.36 to 1.60m. Flooding is unlikely at this level.
Is the river level rising or falling at Farnborough?
Based on the most recent readings, the level is currently rising. 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. Only about 7.6mm of rain has fallen nearby in the last 7 days, so the flow is being sustained mainly by groundwater. 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 Blackwater at Farnborough?
The typical range at this station is 0.36m to 1.60m, based on Environment Agency historical data. Levels above 1.60m 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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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:
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