Polluted by sewage 162 times in 2025 - lasting 1,865 hours
Chichester Harbour was the #27 most polluted Area of Outstanding Natural Beauty in England & Wales, by duration of sewage overflows, as reported by the water companies
Storm overflows spill when it rains, and 2025 was drier than 2024 - 90% of average annual rainfall against 105%.
So much of any drop is weather, not fixed pipes. The live page shows rainfall and sewage side by side, day by day.
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Donate NowHere are all the reported sewage overflow totals for Chichester Harbour in 2025.
A CSO Combined Sewage Overflow - a device that, when operating, pours combined rainwater & sewage into a waterway counts towards Chichester Harbour when it sits inside the designated area, or within 200 metres of its boundary. An overflow close to two AONBs is counted in both.
We use data from the water companies, but we are seeing many anomalies that make us believe that location information is quite poor. The situation is likely far worse than reported here.
Other CSO Combined Sewage Overflow - a device that, when operating, pours combined rainwater & sewage into a waterway s just outside the 200 metre boundary are not counted, though they may still affect water quality inside the area.
| Company | Waterway | Site | Sewage Dumps | Duration (Hours) | Reporting % |
|---|---|---|---|---|---|
| Southern Water | Chichester Harbour | CHICHESTER WWTW | 62 | 984 | 98.3 |
| Southern Water | Chichester Hbr Via Little Deep | THORNHAM WWTW | 21 | 236 | 100 |
| Southern Water | Chichester Harbour Channel | BOSHAM WWTW | 22 | 220 | 100 |
| Southern Water | Ham Brook | CSO BREAKERS YARD NUTBOURNE | 19 | 189 | 99.3 |
| Southern Water | Chichester Hbr Via Little Deep | THORNHAM WWTW | 12 | 118 | 100 |
| Southern Water | Chichester Harbour | MAIN ROAD FISHBOURNE CSO | 8 | 46 | 100 |
| Southern Water | Ham Brook | SCHOOL LANE PS | 2 | 23 | 100 |
| Southern Water | To Chichester Harbour | CHIDHAM LANE SPS CHIDHAM | 3 | 18 | 100 |
| Southern Water | Nore Rithe/Emsworth Harbour | KINGS ROAD EMSWORTH CSO | 2 | 10 | 99.9 |
| Southern Water | Chichester Harbour | TAYLORS LANE BOSHAM, WWPS | 3 | 8 | 100 |
| Southern Water | Chichester Hbr Via Little Deep | THORNHAM WWTW | 4 | 5 | 100 |
| Southern Water | Chichester Harbour | CHICHESTER WWTW | 4 | 3 | 98.3 |
EDM (Event Duration Monitoring) data and Consented Discharges to Controlled Waters with Conditions from Environment Agency & Data Map Wales, and Scottish Water
Experimental derived data from Thames Water API, Some data may be missing or inaccurate. Live sewage data from Stream Water API
Annual figures up to and including 2025 come from official water company returns. The 2026 figure is our own estimate, derived continuously from the companies' live data feeds.
Uses Environment Agency rainfall data from the real-time data API (Beta) - Rainfall data is delayed by up to two days.
This website is intended to provide an accurate representation of the Environment Agency data. The data is hard to use, and thus some errors may have been made. If you find something that is incorrect, please raise an issue at the GitHub issues page and we'll endeavour to fix it quickly.
This project is not associated, approved or endorsed by any of the companies whose logos you see here.