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Home › Rivers › Carnon River

Carnon River water levels

Live levels from 1 monitoring station across Cornwall, updated every 15 minutes.

1stations
0above typical high

Gauges

Monitoring stations, source to mouth

StationTownLevel nowStatusTrend
BissoeBissoe0.26 m 1h agoNormal—

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.

Gauged tributaries

Streams and rivers with a gauge whose water joins the Carnon River above one of its gauges, from the source down. The river map knows where gauges are, not every stream, so a tributary without a gauge is not listed here.

No gauged tributary joins the Carnon River above Bissoe on the river map. Streams without a gauge are not counted here.

Where the Carnon River goes

No gauge below Bissoe is known on the river map.

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.

Storm overflows upstream

2 storm overflows are traced upstream of Bissoe, the Carnon River’s lowest gauge on the river map: on the Carnon River itself, on its gauged tributaries, and on smaller streams that join above there.

  • 0 report discharging now
  • 2 not discharging
  • 0 offline or silent: 0 monitor offline, 0 status unknown, 0 no live feed

Official figures for 2025, for the overflows traced upstream of Bissoe: 154 spills over 2,701 hours in total, across all 2.

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 the Carnon River includes the smaller streams that join it there.

Above Bissoe, the Carnon River’s highest gauge2 overflows
  • Gwennap Wastewater Treatment Works Not discharging
    South West Water · into Hicks Mill Stream · 3.1 km by river above Bissoe · 2025: 13 spills, 28 h · placed on the river by its position alone
  • Gwennap Wastewater Treatment Works Not discharging
    South West Water · into Hicks Mill Stream · 3.1 km by river above Bissoe · 2025: 141 spills, 2,673 h · placed on the river by its position alone

Near these gauges, connection not known

Within 3 km of one of the Carnon River’s gauges in a straight line, but the river map cannot say whether their water reaches it.

  • Quenchwell Pumping Station Not discharging shellfish water
    South West Water · into Trib Of Carnon River · 2.2 km from Bissoe in a straight line · its watercourse is not on the river map · 2025: 27 spills, 182 h
  • Devoran Pumping Station Not discharging shellfish water
    South West Water · into River Carnon Estuary(E) · 2.6 km from Bissoe in a straight line · discharges to the sea, an estuary or tidal water · 2025: 9 spills, 56 h

1 other overflow within 3 km of these gauges is placed below the Carnon River’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: © South West 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.

Water samples

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.

20 sampling points on the Carnon River and the streams that join it above Bissoe, and below it. 7 have a sample from the last 12 months; 10 have any sample banked. Listed from the source down, grouped by the next gauge each one's water reaches.

Above Bissoe Carnon River 16 points, 6 with samples
Sampling pointWatercourse (map)Above the gaugeLast sampleLatest results (river water)
Hicks Mill Stream at Penpons Millunnamed stream5.5 kmLast sampled 16 Apr 2018, before the imported period
Hicks Mill Stream at Penventonunnamed stream5.2 kmLast sampled 2 Feb 2018, before the imported period
Hicks Mill Stream at Comfordunnamed stream4.8 kmLast sampled 16 Apr 2018, before the imported period
Hicks Mill Stream at Gwennap Churchunnamed stream4.3 kmLast sampled 30 Nov 2017, before the imported period
Hicks Mill Stream upstream of Lanner St Day sewage treatment worksunnamed stream3.4 kmLast sampled 24 Feb 2020, before the imported period
Hicks Mill Stream downstream of Lanner St Day sewage treatment worksunnamed stream2.9 km7 Jul 2026 · 3 months agopH 7.19
Hicks Mill Stream at Trehaddleunnamed stream2.1 km9 Mar 2026 · 7 months agoOxygen 96.2%Temp 12.4 °CpH 6.98Conductivity 203 µS/cm
Carnon at Twelveheads upstream of St Day StreamCarnon River1.9 kmLast sampled 17 Jun 2019, before the imported period
Hicks Mill Stream upstream of Frogpool sewage treatment worksunnamed stream1.8 kmLast sampled 24 Feb 2011, before the imported period
Carnon at Twelveheads downstream of St Day StreamCarnon River1.6 km24 Jul 2026 · 2 months agoOxygen 99.9%Temp 16.1 °CpH 7.25Conductivity 309 µS/cm
Carnon downstream of County Adit (Culverted Stretch)Carnon River1.4 km24 Jul 2026 · 2 months agoOxygen 68.8%Temp 14.9 °CpH 5.15Conductivity 324 µS/cm
Carnon River below County and Wellington AditsCarnon River1.1 kmLast sampled 8 Nov 2019, before the imported period
River Carnon G Station at Nangiles AditCarnon River1.0 kmLast sampled 12 Jan 2000, before the imported period
Hicks Mill Stream at Hicks Millunnamed stream0.9 km26 Mar 2024 · 2.5 years agopH 7.1
River Carnon at Point MillsCarnon River0.6 kmLast sampled 31 May 2018, before the imported period
Carnon River at Bissoe Bridge Gauging StationCarnon River0.1 km24 Jul 2026 · 2 months agoOxygen 91.8%Temp 15.6 °CpH 5.85Conductivity 318 µS/cm
Below Bissoe 4 points
Sampling pointWatercourse (map)Below the gaugeLast sampleLatest results (river water)
River Carnon upstream of Grenna BridgeCarnon River1.0 km24 Jul 2026 · 2 months agoOxygen 91.8%Temp 15.6 °CpH 6.14Conductivity 654 µS/cm
Helstone Water upstream of Carnon at GrennaCarnon River1.0 km2 Jul 2025 · 15 months agoOxygen 86.3%Temp 15.9 °CpH 7.1Conductivity 265 µS/cm
Carnon River upstream of Devoran sewage treatment worksCarnon River1.9 km19 Aug 2025 · 14 months agoOxygen 89.5%Temp 15.3 °CpH 6.17Conductivity 708 µS/cm
Carnon River at Devoran BridgeCarnon River2.6 km17 Aug 2026 · 52 days agoOxygen 94.7%Temp 16.8 °CpH 6.19Ammonia 0.11 mg/l

Distances are along the river to the gauge named. England's samples only.

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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