WaterWatch — Thames Water CSO Discharge Monitor

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Now live — Thames Water region · updated every 15 min

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When a sewer overflows into your river, you deserve to know about it. WaterWatch puts real‑time discharge data from every Thames Water CSO site into plain sight — when it started, how long it ran, and exactly where on the map.

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Why we exist

Environmental data that belongs to everyone.

Discharge records from every Thames Water CSO site are publicly available — reported through an official EDM sensor network, updated every 15 minutes. WaterWatch makes that data actually usable.

Real-time alerts. Site histories. River-level context. Weekly summaries. Every number comes from the source, presented clearly. Independent, transparent, and free for everyone.

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The platform

Track every discharge.

Every CSO site in the Thames Water network — mapped, measured, and updated every 15 minutes from official EDM sensor data. Free and independent.

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Live discharge map

Every active overflow plotted in real time from Thames Water EDM sensors, refreshed every 15 minutes.

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Per-site discharge history

Full event records for any site — start time, duration, and cumulative spill hours by month and year.

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Instant email alerts

Get notified the moment a discharge starts or stops at a site you follow. Free, no spam.

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CSV data export

Download raw discharge data for any site or date range for your own research.

Live discharges, offline monitors and year-on-year network trend in one place.

Every Thames Water CSO site ranked by total spill hours and event count.

Monday morning email: worst sites, rivers, rainfall, and total hours spilled.

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EA data

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Rainfall & river context

Live EA river levels and rainfall readings alongside every discharge event.

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From the blog

Transparency in practice

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Methodology16 Mar 2026 · 10 min read

How we determine if a CSO site is improving

Reducing spill hours year-on-year sounds straightforward. It isn't. Rainfall, sensor gaps, and three-year baselines all complicate the picture. Here's our honest framework for reading improvement signals.

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Transparency15 Mar 2026 · 8 min read

Why you can trust what WaterWatch tells you

Every number on WaterWatch comes from Thames Water's own EDM sensor network. We don't estimate, extrapolate, or fill gaps. Here's exactly how our pipeline works — and where its limits honestly lie.

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Built by people who give a damn

WaterWatch is an independent project. No investor pressure, no corporate agenda — just a belief that environmental data should be genuinely accessible.

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