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Area of Outstanding Natural Beauty

Chichester Harbour

Polluted by sewage 162 times in 2025 - lasting 1,865 hours

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Totals for Chichester Harbour in 2025

12 Sites polluted by Southern Water
162 sewage dumps
1,865 hours duration
That's 2.59 months. 3.1 times a week, on average

How does Chichester Harbour compare?

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

Why the change?

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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Pollution Summary 2025

Here are all the reported sewage overflow totals for Chichester Harbour in 2025.

How we count, and how accurate it is

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

Data Sources & Accuracy

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.