Semley Inlet
Storm overflow operated by Wessex Water. The source names Tributary of River Sem as the receiving water.
- 17
- Spills in 2025
- 39
- Recorded hours
- 99.8%
- Monitor operation
- 4
- Years listed
The reported spill count was 7 lower than in 2024. This compares event counts, not discharge volume.
Checking the latest monitor report…
How it compares in 2025
Semley Inlet recorded 17 spills in 2025. That is more than 59% of the 14,239 overflows in England with a reported figure, and ranks 5,597th nationally. Among Wessex Water overflows it ranks 512th of 1,332; the median Wessex Water overflow recorded 11 spills.
| Group | Rank by spills | Median spills | Median hours |
|---|---|---|---|
| This outlet | – | 17 | 39 |
| England | 5,597th of 14,239 | 11 | 22.3 |
| Wessex Water | 512th of 1,332 | 11 | 18.9 |
Rank 1 has the most spills. Equal counts share a rank. Only overflows with a reported count are ranked. Counts do not measure volume, so a higher rank does not mean more sewage.
Annual spill history
| Year | Spills | Duration | Monitor operation | Source |
|---|---|---|---|---|
| 2025 | 17 | 39 hours | 99.8% | Official data |
| 2024 | 24 | 53 hours | 100% | Official data |
| 2023 | 15 | 17 hours | 100% | Official data |
| 2022 | 20 | 19 hours | 99.9% | Official data |
A missing figure means the source did not provide a usable value. A zero is shown as zero. Monitor operation below 90% can make comparison less reliable.
Outlet details
- Water company
- Wessex Water
- Outlet type
- Inlet storm overflow at a wastewater treatment works
- Permit
- 040076
- Activity reference
- 2-STORM DISCHARGE AT STW (UNTREATED)
- Grid reference
- ST8743826938
- Waterbody ID
- GB108043016210Official waterbody record ↗
- Location source
- Official annual grid reference
- Location precision
- About 1 metres
- Location note
- Unknown
About the name and type
The annual return lists this asset as “Inlet SO at WwTW”: inlet storm overflow at a wastewater treatment works. The overflow is at the inlet of a treatment works, where wastewater enters the works.
The waterbody link opens the Environment Agency record for the exact ID in the return. It is a source lookup; we do not import its classification.
Where it is
The recorded position is about 3 km north-east of the Motcombe reference point in the ONS built-up areas data.
Area and water pages
Check the official record
Public access to this outlet is unknown. Do not enter restricted land or use this page as a route guide.
Open official source ↗Other outlet records nearby
- Hindon InletCurrent status unknown
Wessex Water · Groundwater via Infilt System
- Hindon The DeneCurrent status unknown
Wessex Water · Tributary of the River Nadder
- Tisbury Nadder Close Playing FieldsCurrent status unknown
Wessex Water · River Nadder via SWS
- ChilmarkCurrent status unknown
Wessex Water · Tributary of the River Nadder
Questions about Semley Inlet
- Who operates Semley Inlet?
- Wessex Water is the operator named in the annual record. The permit reference is 040076.
- Where does Semley Inlet discharge?
- The source names Tributary of River Sem as the receiving water. This does not show how far a discharge travelled.
- How many times did Semley Inlet spill in 2025?
- The 2025 return records 17 counted spill events and 39 hours of recorded discharge. Spills are counted with the 12/24-hour method, so this is not a count of every start signal.
- Can I trust the 2025 figures for this outlet?
- The monitor worked for 99.8% of the reporting period, so the annual figures cover most of the year. They still do not measure discharge volume.
- Is Semley Inlet discharging right now?
- This record is linked to a company live feed. The panel above shows the latest report we hold, with its date. That report can be old, and the monitor can be offline, so check the date before relying on it. A report that no discharge is taking place is not a water-quality result.
- How accurate is the map marker?
- The marker comes from the grid reference in the official annual return, which is accurate to about 1 metres. It shows the recorded outlet position, not the extent of any discharge.
- What kind of outlet is Semley Inlet?
- The annual return lists the asset type as “Inlet SO at WwTW”, which means inlet storm overflow at a wastewater treatment works. The overflow is at the inlet of a treatment works, where wastewater enters the works.
- How does Semley Inlet compare with other overflows?
- Semley Inlet recorded 17 spills in 2025. That is more than 59% of the 14,239 overflows in England with a reported figure, and ranks 5,597th nationally. Among Wessex Water overflows it ranks 512th of 1,332; the median Wessex Water overflow recorded 11 spills. Ranks compare counted spill events only. They do not compare volume or harm.
- Does zero spills mean the water was safe?
- No. A zero means the annual return recorded zero counted spill events for this outlet and year. It is not a water-quality test, and pollution can come from other sources.