Northumbrian Water storm overflows in 2025
What the official annual return shows for Northumbrian Water’s storm overflows in England, compared with 2024 and with the other water companies.
Summary
The 2025 annual return lists 1,561 storm overflows run by Northumbrian Water in England. 1,559 have a usable spill count. Together they recorded 27,860 spills and 123,803 hours of discharge. The median outlet recorded 11 spills and 15.6 hours.
For a fair comparison with 2024, we use only the 1,205 outlets with a count in both years and a monitor that worked at least 90% of each year. Their spills went from 32,796 to 22,088, a fall of 33%. 834 recorded fewer spills and 199 recorded more.
255 outlets (16.4%) recorded no spills in 2025. 72 (4.6%) recorded 60 or more.
Northumbrian Water’s median of 11 spills per outlet is the 5th highest of the 10 companies in the return. The England median is 11.
202 outlets had a monitor that worked for less than 90% of the year. Counts from those outlets may be low.
- 1,561
- Outlets listed
- 27,860
- Spills in 2025
- 11
- Median per outlet
- 123,803
- Recorded hours
How many spills each outlet recorded
Outlets with a usable 2025 count, grouped by the number of spills. The longest bar is the largest group.
- 0
- 255 16.4%
- 1 to 9
- 490 31.4%
- 10 to 19
- 267 17.1%
- 20 to 39
- 332 21.3%
- 40 to 59
- 143 9.2%
- 60 or more
- 72 4.6%
Spills over time
The median outlet run by Northumbrian Water recorded 11 spills in 2025, against 11 across England.
1,205 outlets have a comparable count for both 2024 and 2025, with the monitor working at least 90% of each year. 199 recorded more spills, 834 fewer and 172 the same. Together they went from 32,796 to 22,088 spills, a fall of 33%.
Largest rises from 2024 to 2025
- Sedgeletch STW2 → 87
- Winston STW5 → 45
- Greatham STW11 → 46
| Year | Outlets with a count | Total spills | Median per outlet | England median |
|---|---|---|---|---|
| 2025 | 1,559 | 27,860 | 11 | 11 |
| 2024 | 1,549 | 40,670 | 17 | 19 |
| 2023 | 151 | 7,096 | 42 | 20 |
| 2022 | 122 | 3,138 | 18 | 13 |
| 2021 | 114 | 4,218 | 34 | 19 |
| 2020 | 64 | 2,057 | 26.5 | 18 |
Earlier returns list fewer of these outlets, so totals are not comparable between years. The median per outlet and the like-for-like change are fairer comparisons. Counts are events, not volume.
Largest falls from 2024 to 2025
Only outlets with a count in both years and at least 90% monitor operation in each. Counts depend on rainfall as well as on the sewer network, so a fall does not show on its own that an overflow improved.
- Felton STW216 → 109
- Allendale STW202 → 106
- Howdon STW214 → 120
- Boldron STW112 → 19
- Ouseburn East PS99 → 12
- Wagonway Road SPS179 → 100
- North Blyth SPS105 → 31
- Staindrop Sewage Treatment Works82 → 9
- Whorlton STW92 → 19
- Shilbottle STW142 → 74
Most spills in 2025
- 1Cotherstone STW161spills
River Balder
- 2Glasshouse Street PS128spills
River Tyne, North Sea
- 3121spills
- 4Howdon STW120spills
River Tyne Saline Estuary
- 4Otterburn STW120spills
River Rede
- 6Howdon STW113spills
River Tyne Saline Estuary
- 6Moorsholm Sewage Treatment Works113spills
Hagg Beck (Kilton Beck Tributary)
- 8Felton STW109spills
Coquet
- 9Western Area STW107spills
River Wear
- 10Allendale STW106spills
River East Allen
Most hours in 2025
- 1Cotherstone STW2,197hours
River Balder
- 2Allendale STW1,865hours
River East Allen
- 3Western Area STW1,822hours
River Wear
- 4Otterburn STW1,816hours
River Rede
- 5Felton STW1,454hours
Coquet
- 6Glasshouse Street PS1,353hours
River Tyne, North Sea
- 7Graythorp STW1,349hours
Greatham Creek/SEATON Channel
- 8Howdon STW1,238hours
River Tyne Saline Estuary
- 9Swainby STW1,236hours
Potto Beck
- 10Milfield Sewage Treatment Works1,193hours
Unnamed Tributary River Till
Waterbodies with the most spills
Total 2025 spills from outlets the return links to each waterbody. A waterbody with more outlets will usually have a higher total.
| Waterbody | Outlets | Spills | Spills per outlet |
|---|---|---|---|
| Tyne | 177 | 3,605 | 20.4 |
| Tees | 40 | 965 | 24.1 |
| Team from Source to Tyne | 56 | 829 | 14.8 |
| Tyne and Wear | 55 | 804 | 14.6 |
| Wear from Gaunless to Browney | 30 | 652 | 21.7 |
| Derwent from Burnhope Burn to River Tyne | 55 | 636 | 11.6 |
| Tyne from Watersmeet to Tidal Limit | 41 | 597 | 14.6 |
| Tweed | 32 | 595 | 18.6 |
| Wear from Croxdale Beck to Lumley Park Burn | 46 | 568 | 12.3 |
| Tees from Skerne to Tidal Limit | 34 | 563 | 16.6 |
How to read this report
- A spill is a counted event under the 12/24-hour method. It is not a volume, and it does not measure harm or water quality.
- Missing counts are left out, not treated as zero. Low monitor operation can make a count too low.
- Rankings compare counts only. They do not show whether an overflow broke its permit or the law.
- Earlier years list fewer outlets, so compare medians or like-for-like groups, not totals.
Data: Environment Agency event duration monitoring annual returns, Open Government Licence v3.0. How spills are counted · How the data works · Sources