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 2.8 km away along the river. 0 report discharging now, 3 report not discharging.
Southern Water · into Bartley Water (Tidal) · 5.7 km away in a straight line · discharges to the sea, an estuary or tidal water
12 spills · 70 hours in 2025
Not discharging now · last
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 →
🌊 Fairly flashyResponds fairly quickly to rain, with moderate baseflow between events.
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
0.48
mixed response
Avg Annual Rainfall
912 mm/yr
1991–2020 · +5% since 1941–70
Urban Extent
1.5%
largely rural
Median Annual Flood
14.79 m³/s
QMED — typical yearly peak flow
Highest Daily Mean Flow
21.00 m³/s
24 Dec 1999 · 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.
Crump weir with velocity area for higher flows gauging a predominantly rural, natural catchment.
More detail
The catchment
Predominantly rural catchment of meadows, woodland and heath underlain by Tertiary sands, gravels and clays (mainly impervious in the lower catchment). The catchment includes numerous small and medium sized towns in the area between Southampton & Salisbury. The River Blackwater drains the catchment in a south easterly direction. The river meanders across the floodplain & then below the A3090 dual carriageway.
The station
Crump profile weir, crest width 6.16m, with pressure transducer downstream. Located 10km upstream of the confluence of the River Blackwater with the River Test. Stage measured in stilling well inside hut on upstream side of weir. Downstream stage stopped being recorded in 2009.
How it measures flow
The weir crest has a 1cm variation which does not conform to British Standard guidelines, the gauge is not within a straight section of channel and the channel turns sharply downstream to pass under the A3090 culvert. Velocity area calibration used for medium and high flows up to 1.85m (approx. 10 cumecs); includes allowance for floodplain discharge. No bypassing occurs at the culvert 50m downstream. There is also a small footbridge 100m downstream and another 1.5m upstream where water spills out of bank long before the soffit level is reached (1.31m stage). The channel in the vicinity of the gauge has vertical sheet piling - this continues, along with concrete banks, to the downstream culvert. Silt islands with vegetation growing on them exist in the channel. Significant vegetation growth directly upstream and downstream (sharp bend) of station; requires significant flood event to clear channel. One peak flow rating applied across period of record. Hydraulic modelling used to extended rating to 3.1m stage, fits gaugings well.
Flow regime
A responsive catchment. Negligible net impact of artificial influences (cress beds in headwaters and very minor amount of spray irrigation. Natural to within 10% at Q95.
The flow record
Good record since the late 1970s. Full period of record peak flow data reviewed and released in September 2020 (WINFAP Files v9).
How this gauging station is built and how long it has measured (NRFA / UKCEH).
Gauge type
Crump weir
Operating since
1976
Station datum
7.6 mAOD
Flow record
1976–2024 · 48 yrs · 100% complete
Peak-flow record
since 1976
Hydrometric area
42
Measured by
Environment Agency
Nearby Groundwater
Soil Moisture
Frequently asked questions
Is OWER GS flooding today?
The latest recorded level is 0.16m. Compare it with the recent history on the chart above to judge whether levels are unusually high.
Is the river level rising or falling at OWER GS?
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.
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.
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
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10 Jul 2013 Low flow gauging section
10 Jul 2013 Weir
11 Sep 2012 View upstream
11 Sep 2012 Stage board
29 Aug 2012 Weir
29 Aug 2012 View downstream
29 Aug 2012 Gauging hut
Upstream view to gauging station