River Menalhyl at St Mawgan Bridge
EA name: RIVER MENALHYL AT ST. MAWGAN BRIDGE
Environment Agency sampling point SW-82511119 · Freshwater - rivers · listed as open (“open” does not mean it is sampled now)
These are samples taken on a date, not live readings of the river. Results reach the Environment Agency's archive days to months after the sample is taken, so the newest here may be weeks or months old. FloodRadar does not grade them.
Where and when
- Last sampled
- 27 Aug 2026, 08:5135 days ago · time as the Environment Agency records it (UK clock time; the source gives no time zone)
- Samples banked
- 5 since 10 Apr 2026 Imported periods: 1 Oct 2023 – 30 Sep 2026. Samples outside them are not shown here.
- Latest sample
- River / running surface water Environmental monitoring statutory (EU directives)
- Where
- National Grid 187258, 65991As published, to the nearest 1 m. Open in a map
- River, by its own name
- Menalhyl
- River, by the map
- River MenalhylPlaced on the river its name gives, 8 m from the line.
- Next gauge downstream
- None tracedIts water reaches the sea without passing a gauge.
- Why it was sampled
- Environmental monitoring statutory (EU directives) (5 samples)
Main measurements, river water
Dissolved oxygen
% saturation · code 9901 · %
97.6%
Sampled 27 Aug 2026, 35 days ago · 5 results banked
Every result (5)
| Sampled | Result as published | Reads as |
|---|---|---|
| 27 Aug 2026, 08:51 | 97.6 | 97.6% |
| 14 Jul 2026, 12:18 | 102.3 | 102.3% |
| 8 Jun 2026, 10:13 | 98.2 | 98.2% |
| 5 May 2026, 13:47 | 99.5 | 99.5% |
| 10 Apr 2026, 10:23 | 100.8 | 100.8% |
Dissolved oxygen
as O2 · code 9924 · mg/l
9.39 mg/l
Sampled 27 Aug 2026, 35 days ago · 5 results banked
Every result (5)
| Sampled | Result as published | Reads as |
|---|---|---|
| 27 Aug 2026, 08:51 | 9.39 | 9.39 mg/l |
| 14 Jul 2026, 12:18 | 9.37 | 9.37 mg/l |
| 8 Jun 2026, 10:13 | 10.2 | 10.2 mg/l |
| 5 May 2026, 13:47 | 10.6 | 10.6 mg/l |
| 10 Apr 2026, 10:23 | 11.3 | 11.3 mg/l |
Water temperature
code 0076 · °C
17.1 °C
Sampled 27 Aug 2026, 35 days ago · 5 results banked
Every result (5)
| Sampled | Result as published | Reads as |
|---|---|---|
| 27 Aug 2026, 08:51 | 17.1 | 17.1 °C |
| 14 Jul 2026, 12:18 | 19.5 | 19.5 °C |
| 8 Jun 2026, 10:13 | 13.6 | 13.6 °C |
| 5 May 2026, 13:47 | 12.6 | 12.6 °C |
| 10 Apr 2026, 10:23 | 10.1 | 10.1 °C |
pH
code 0061
7.4
Sampled 27 Aug 2026, 35 days ago · 5 results banked
Every result (5)
| Sampled | Result as published | Reads as |
|---|---|---|
| 27 Aug 2026, 08:51 | 7.4 | 7.4 |
| 14 Jul 2026, 12:18 | 7.86 | 7.86 |
| 8 Jun 2026, 10:13 | 7.72 | 7.72 |
| 5 May 2026, 13:47 | 7.87 | 7.87 |
| 10 Apr 2026, 10:23 | 7.89 | 7.89 |
Ammonia
ammoniacal nitrogen as N · code 0111 · mg/l
below 0.03 mg/l (not detected above this)
Sampled 27 Aug 2026, 35 days ago · 5 results banked
Every result (5)
| Sampled | Result as published | Reads as |
|---|---|---|
| 27 Aug 2026, 08:51 | <0.03 | below 0.03 mg/l (not detected above this) |
| 14 Jul 2026, 12:18 | <0.03 | below 0.03 mg/l (not detected above this) |
| 8 Jun 2026, 10:13 | <0.03 | below 0.03 mg/l (not detected above this) |
| 5 May 2026, 13:47 | <0.03 | below 0.03 mg/l (not detected above this) |
| 10 Apr 2026, 10:23 | <0.03 | below 0.03 mg/l (not detected above this) |
Nitrate
as nitrogen (N) · code 0117 · mg/l
12 mg/l
Sampled 27 Aug 2026, 35 days ago · 5 results banked
Every result (5)
| Sampled | Result as published | Reads as |
|---|---|---|
| 27 Aug 2026, 08:51 | 12 | 12 mg/l |
| 14 Jul 2026, 12:18 | 12 | 12 mg/l |
| 8 Jun 2026, 10:13 | 5.89 | 5.89 mg/l |
| 5 May 2026, 13:47 | 6.19 | 6.19 mg/l |
| 10 Apr 2026, 10:23 | 5.98 | 5.98 mg/l |
Phosphate
orthophosphate, reactive, as P · code 0180 · mg/l
0.15 mg/l
Sampled 27 Aug 2026, 35 days ago · 5 results banked
Every result (5)
| Sampled | Result as published | Reads as |
|---|---|---|
| 27 Aug 2026, 08:51 | 0.15 | 0.15 mg/l |
| 14 Jul 2026, 12:18 | 0.25 | 0.25 mg/l |
| 8 Jun 2026, 10:13 | 0.06 | 0.06 mg/l |
| 5 May 2026, 13:47 | 0.067 | 0.067 mg/l |
| 10 Apr 2026, 10:23 | 0.036 | 0.036 mg/l |
Conductivity
at 25 °C · code 0077 · µS/cm
387 µS/cm
Sampled 27 Aug 2026, 35 days ago · 5 results banked
Every result (5)
| Sampled | Result as published | Reads as |
|---|---|---|
| 27 Aug 2026, 08:51 | 387 | 387 µS/cm |
| 14 Jul 2026, 12:18 | 380 | 380 µS/cm |
| 8 Jun 2026, 10:13 | 252 | 252 µS/cm |
| 5 May 2026, 13:47 | 289 | 289 µS/cm |
| 10 Apr 2026, 10:23 | 329 | 329 µS/cm |
Everything measured here
12 determinands, each kept by its code, unit and sample material: results in different units or on different materials are never mixed. A “below” result is under the laboratory's detection limit, not zero.
Show all 12 rows
| Determinand | Material | Results | First – last | Latest result |
|---|---|---|---|---|
| Oxygen, Dissolved, % Saturation 9901 | River water | 5 | Apr 2026 – Aug 2026 | 97.6% 27 Aug 2026 |
| Oxygen, Dissolved as O2 9924 | River water | 5 | Apr 2026 – Aug 2026 | 9.39 mg/l 27 Aug 2026 |
| Temperature of Water 0076 | River water | 5 | Apr 2026 – Aug 2026 | 17.1 °C 27 Aug 2026 |
| pH 0061 | River water | 5 | Apr 2026 – Aug 2026 | 7.4 27 Aug 2026 |
| Ammoniacal Nitrogen as N 0111 | River water | 5 | Apr 2026 – Aug 2026 | below 0.03 mg/l 27 Aug 2026 |
| Nitrate as N 0117 | River water | 5 | Apr 2026 – Aug 2026 | 12 mg/l 27 Aug 2026 |
| Orthophosphate, reactive as P 0180 | River water | 5 | Apr 2026 – Aug 2026 | 0.15 mg/l 27 Aug 2026 |
| Conductivity at 25 C 0077 | River water | 5 | Apr 2026 – Aug 2026 | 387 µS/cm 27 Aug 2026 |
| Alkalinity to pH 4.5 as CaCO3 0162 | River water | 5 | Apr 2026 – Aug 2026 | 46 mg/l 27 Aug 2026 |
| Ammonia un-ionised as N 0119 | River water | 5 | Apr 2026 – Aug 2026 | below 0.00024 mg/l 27 Aug 2026 |
| Nitrite as N 0118 | River water | 5 | Apr 2026 – Aug 2026 | 0.032 mg/l 27 Aug 2026 |
| Nitrogen, Total Oxidised as N 0116 | River water | 5 | Apr 2026 – Aug 2026 | 12 mg/l 27 Aug 2026 |
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.