WaterWatch — Thames Water CSO Discharge Monitor

WaterWatch

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Thames Water Region · Live Intelligence

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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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Quick views

Jump straight into the live tools — dashboard, rankings, map, and status.

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Network dashboard

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

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Site rankings

See the worst CSO sites by spill hours and events.

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Live map

Every monitored site plotted with live discharge status.

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System status

Independent status page for API, portal, alerts and data quality.

New2025 annual discharge data is now available · View rankings →

·Read our latest blog post · How we measure improvement →

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Sites discharging now

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Network uptime

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Monitors offline

Thames CSO sites monitored

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.

Our story →Read the blog →

“The rivers belong to everyone. So does the information about what's going into them.”

WaterWatch

What WaterWatch does

Everything you need. Nothing you don't.

Live now

The complete picture, updated every 15 minutes.

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Live discharge map

Every active CSO event plotted in real time, sourced directly from Thames Water EDM sensor data. Updated every 15 minutes.

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Per-site history

Drill into any overflow point for a full record of discharge events — start time, duration, and total hours spilling by month and year.

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Instant alerts

Get notified by email the moment a discharge event is recorded at a site you follow. Free, no spam, unsubscribe anytime.

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CSV export

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

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Network dashboard

A live command centre for the entire Thames Water network: discharging, offline, and year-on-year movement at a glance.

Every Thames Water CSO site ranked by total spill hours and event count. Sort by year, time window, or river.

See whether each site is improving or worsening. Year-on-year percentage change, colour-coded clearly.

A Monday morning email with total spill hours, worst sites, most-impacted rivers, and rainfall context.

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River & rainfall data

Live river levels and rainfall from EA gauging stations put every discharge event in environmental context.

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How it works

From sensor to your inbox in minutes.

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Sensor records it

EDM sensors at each CSO site record when discharge starts and stops, reporting to the official network every 15 minutes.

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We ingest it

WaterWatch pulls the latest readings continuously and detects the moment a site transitions to discharging.

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Map updates live

The discharge map reflects the current state of every monitored site in real time — no refresh needed.

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You get notified

If you're subscribed to a site, we fire an alert the moment we detect it starts or stops discharging.

From the blog

Transparency in practice

All posts →

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.

Read →

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.

Read →

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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Be the first to know when it happens.

Sign up for free and get an immediate alert the moment a site near you starts discharging. Email and SMS both supported. No spam, no paywall, unsubscribe at any time.

Or browse the map and click any site to subscribe