The Postern Somerhill Stream
EA name: THE POSTERN SOMERHILL STREAM (also listed as “THE POSTERN TONBRIDGE SOMERHILL STREAM”)
Environment Agency sampling point SO-E0000768 · 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
- 10 Mar 2025, 14:0619 months ago · time as the Environment Agency records it (UK clock time; the source gives no time zone). Not sampled since, as far as the archive shows: the Environment Agency was asked up to 30 Sep 2026 and had nothing newer.
- Samples banked
- 10 since 7 Jun 2024 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 560659, 146139As published, to the nearest 1 m. Open in a map
- River, by its own name
- Its name does not give one
- River, by the map
- Southborough StreamPlaced by position alone, on a line whose map name differs from its own, 2 m from the line.
- Next gauge downstream
- Hartlake Bridge On the River Medway · 3.4 km along the river
- Why it was sampled
- Environmental monitoring statutory (EU directives) (10 samples)
Main measurements, river water
Dissolved oxygen
% saturation · code 9901 · %
97.3%
Sampled 10 Mar 2025, 19 months ago · 10 results banked
Every result (10)
| Sampled | Result as published | Reads as |
|---|---|---|
| 10 Mar 2025, 14:06 | 97.3 | 97.3% |
| 12 Feb 2025, 12:59 | 98.8 | 98.8% |
| 8 Jan 2025, 13:13 | 95.4 | 95.4% |
| 4 Dec 2024, 08:46 | 93.5 | 93.5% |
| 8 Nov 2024, 09:07 | 89.5 | 89.5% |
| 2 Oct 2024, 10:08 | 92.8 | 92.8% |
| 5 Sep 2024, 10:13 | 92.2 | 92.2% |
| 2 Aug 2024, 10:38 | 80.4 | 80.4% |
| 3 Jul 2024, 13:07 | 91.3 | 91.3% |
| 7 Jun 2024, 10:07 | 89.6 | 89.6% |
Dissolved oxygen
as O2 · code 9924 · mg/l
10.7 mg/l
Sampled 10 Mar 2025, 19 months ago · 10 results banked
Every result (10)
| Sampled | Result as published | Reads as |
|---|---|---|
| 10 Mar 2025, 14:06 | 10.7 | 10.7 mg/l |
| 12 Feb 2025, 12:59 | 11.9 | 11.9 mg/l |
| 8 Jan 2025, 13:13 | 11.5 | 11.5 mg/l |
| 4 Dec 2024, 08:46 | 11.1 | 11.1 mg/l |
| 8 Nov 2024, 09:07 | 9.67 | 9.67 mg/l |
| 2 Oct 2024, 10:08 | 9.52 | 9.52 mg/l |
| 5 Sep 2024, 10:13 | 8.94 | 8.94 mg/l |
| 2 Aug 2024, 10:38 | 7.45 | 7.45 mg/l |
| 3 Jul 2024, 13:07 | 9.2 | 9.2 mg/l |
| 7 Jun 2024, 10:07 | 9.33 | 9.33 mg/l |
Water temperature
code 0076 · °C
11.1 °C
Sampled 10 Mar 2025, 19 months ago · 10 results banked
Every result (10)
| Sampled | Result as published | Reads as |
|---|---|---|
| 10 Mar 2025, 14:06 | 11.1 | 11.1 °C |
| 12 Feb 2025, 12:59 | 7.1 | 7.1 °C |
| 8 Jan 2025, 13:13 | 7.1 | 7.1 °C |
| 4 Dec 2024, 08:46 | 7.7 | 7.7 °C |
| 8 Nov 2024, 09:07 | 11.8 | 11.8 °C |
| 2 Oct 2024, 10:08 | 14.1 | 14.1 °C |
| 5 Sep 2024, 10:13 | 16.7 | 16.7 °C |
| 2 Aug 2024, 10:38 | 18.9 | 18.9 °C |
| 3 Jul 2024, 13:07 | 14.9 | 14.9 °C |
| 7 Jun 2024, 10:07 | 13.4 | 13.4 °C |
pH
code 0061
7.65
Sampled 10 Mar 2025, 19 months ago · 10 results banked
Every result (10)
| Sampled | Result as published | Reads as |
|---|---|---|
| 10 Mar 2025, 14:06 | 7.65 | 7.65 |
| 12 Feb 2025, 12:59 | 7.7 | 7.7 |
| 8 Jan 2025, 13:13 | 7.58 | 7.58 |
| 4 Dec 2024, 08:46 | 7.54 | 7.54 |
| 8 Nov 2024, 09:07 | 7.62 | 7.62 |
| 2 Oct 2024, 10:08 | 7.65 | 7.65 |
| 5 Sep 2024, 10:13 | 7.56 | 7.56 |
| 2 Aug 2024, 10:38 | 7.44 | 7.44 |
| 3 Jul 2024, 13:07 | 7.61 | 7.61 |
| 7 Jun 2024, 10:07 | 7.71 | 7.71 |
Ammonia
ammoniacal nitrogen as N · code 0111 · mg/l
0.35 mg/l
Sampled 10 Mar 2025, 19 months ago · 10 results banked
Every result (10)
| Sampled | Result as published | Reads as |
|---|---|---|
| 10 Mar 2025, 14:06 | 0.35 | 0.35 mg/l |
| 12 Feb 2025, 12:59 | 0.07 | 0.07 mg/l |
| 8 Jan 2025, 13:13 | 0.16 | 0.16 mg/l |
| 4 Dec 2024, 08:46 | 0.057 | 0.057 mg/l |
| 8 Nov 2024, 09:07 | <0.03 | below 0.03 mg/l (not detected above this) |
| 2 Oct 2024, 10:08 | 0.072 | 0.072 mg/l |
| 5 Sep 2024, 10:13 | 0.042 | 0.042 mg/l |
| 2 Aug 2024, 10:38 | 0.091 | 0.091 mg/l |
| 3 Jul 2024, 13:07 | <0.03 | below 0.03 mg/l (not detected above this) |
| 7 Jun 2024, 10:07 | <0.03 | below 0.03 mg/l (not detected above this) |
Nitrate
as nitrogen (N) · code 0117 · mg/l
11.7 mg/l
Sampled 10 Mar 2025, 19 months ago · 9 results banked
Every result (9)
| Sampled | Result as published | Reads as |
|---|---|---|
| 10 Mar 2025, 14:06 | 11.7 | 11.7 mg/l |
| 12 Feb 2025, 12:59 | 8.06 | 8.06 mg/l |
| 8 Jan 2025, 13:13 | 8.84 | 8.84 mg/l |
| 8 Nov 2024, 09:07 | 19 | 19 mg/l |
| 2 Oct 2024, 10:08 | 8.25 | 8.25 mg/l |
| 5 Sep 2024, 10:13 | 21 | 21 mg/l |
| 2 Aug 2024, 10:38 | 14.9 | 14.9 mg/l |
| 3 Jul 2024, 13:07 | 23 | 23 mg/l |
| 7 Jun 2024, 10:07 | 23 | 23 mg/l |
Phosphate
orthophosphate, reactive, as P · code 0180 · mg/l
0.23 mg/l
Sampled 10 Mar 2025, 19 months ago · 10 results banked
Every result (10)
| Sampled | Result as published | Reads as |
|---|---|---|
| 10 Mar 2025, 14:06 | 0.23 | 0.23 mg/l |
| 12 Feb 2025, 12:59 | 0.19 | 0.19 mg/l |
| 8 Jan 2025, 13:13 | 0.28 | 0.28 mg/l |
| 4 Dec 2024, 08:46 | 0.42 | 0.42 mg/l |
| 8 Nov 2024, 09:07 | 0.46 | 0.46 mg/l |
| 2 Oct 2024, 10:08 | 0.3 | 0.3 mg/l |
| 5 Sep 2024, 10:13 | 0.64 | 0.64 mg/l |
| 2 Aug 2024, 10:38 | 0.43 | 0.43 mg/l |
| 3 Jul 2024, 13:07 | 0.62 | 0.62 mg/l |
| 7 Jun 2024, 10:07 | 0.61 | 0.61 mg/l |
Conductivity
at 25 °C · code 0077 · µS/cm
629 µS/cm
Sampled 10 Mar 2025, 19 months ago · 10 results banked
Every result (10)
| Sampled | Result as published | Reads as |
|---|---|---|
| 10 Mar 2025, 14:06 | 629 | 629 µS/cm |
| 12 Feb 2025, 12:59 | 541 | 541 µS/cm |
| 8 Jan 2025, 13:13 | 543 | 543 µS/cm |
| 4 Dec 2024, 08:46 | 642 | 642 µS/cm |
| 8 Nov 2024, 09:07 | 744 | 744 µS/cm |
| 2 Oct 2024, 10:08 | 512 | 512 µS/cm |
| 5 Sep 2024, 10:13 | 774 | 774 µS/cm |
| 2 Aug 2024, 10:38 | 568 | 568 µS/cm |
| 3 Jul 2024, 13:07 | 765 | 765 µS/cm |
| 7 Jun 2024, 10:07 | 768 | 768 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 | 10 | Jun 2024 – Mar 2025 | 97.3% 10 Mar 2025 |
| Oxygen, Dissolved as O2 9924 | River water | 10 | Jun 2024 – Mar 2025 | 10.7 mg/l 10 Mar 2025 |
| Temperature of Water 0076 | River water | 10 | Jun 2024 – Mar 2025 | 11.1 °C 10 Mar 2025 |
| pH 0061 | River water | 10 | Jun 2024 – Mar 2025 | 7.65 10 Mar 2025 |
| Ammoniacal Nitrogen as N 0111 | River water | 10 | Jun 2024 – Mar 2025 | 0.35 mg/l 10 Mar 2025 |
| Nitrate as N 0117 | River water | 9 | Jun 2024 – Mar 2025 | 11.7 mg/l 10 Mar 2025 |
| Orthophosphate, reactive as P 0180 | River water | 10 | Jun 2024 – Mar 2025 | 0.23 mg/l 10 Mar 2025 |
| Conductivity at 25 C 0077 | River water | 10 | Jun 2024 – Mar 2025 | 629 µS/cm 10 Mar 2025 |
| Alkalinity to pH 4.5 as CaCO3 0162 | River water | 10 | Jun 2024 – Mar 2025 | 82 mg/l 10 Mar 2025 |
| Ammonia un-ionised as N 0119 | River water | 10 | Jun 2024 – Mar 2025 | 0.00312 mg/l 10 Mar 2025 |
| Nitrite as N 0118 | River water | 10 | Jun 2024 – Mar 2025 | 0.29 mg/l 10 Mar 2025 |
| Nitrogen, Total Oxidised as N 0116 | River water | 9 | Jun 2024 – Mar 2025 | 12 mg/l 10 Mar 2025 |
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.