Storm discharge and total daily volume flow data

We want to be open and transparent about our storm discharge activity. You can access data from event duration monitoring (EDM) in the following ways: 

• An interactive map showing storm discharge activity as indicated by our EDM monitors
• Annual storm overflow activity reports showing you data from previous years
• Total daily volume (TDV) data showing the amount of wastewater treated each day
• A third party API, so you can integrate our data into your own systems

Storm discharge map

This map shows you near real-time storm discharge activity, as indicated by our EDM monitors.

You can use the map to see if our monitors indicate:

• That overflows are currently discharging into a watercourse
• The date, time and duration of the last recorded discharge

Although EDM gives us valuable insight to how our storm overflows are working, it isn't always accurate. The monitors are sensitive and can play up. Even the movement of a weed growing in front of the monitor could set it off, indicating that the overflow is active when it isn't.

So when a monitor triggers, we can’t say that a certain section of the watercourse definitely contains sewage, or promise that it’s safe to swim in. EDM doesn't confirm discharges, it only indicates them because the data received might not be accurate. We're being open and sharing our data exactly as we receive it, so you can make more informed choices.

Data quality

We'll be open and transparent if we discover any issues with the quality of our data. See a list of data quality incidents here.

Got any questions?

Take a look at our frequently asked questions page for further information.

Annual reports

Our annual reports show the spill count and duration, as indicated by EDM monitors located at our storm overflows. This is updated by mid-March with data from the previous calendar year.

Total daily volume (TDV) data

We’re also sharing our total daily volume (TDV) flow data. We're required to report this data to the Environment Agency on an annual basis. We've chosen to publish it here, too.

TDV data refers to the total amount of wastewater treated at a sewage works each day (within a 24 hour period). We record total volumes of treated effluent at all our sewage treatment works (STWs), except those treating less than 50 m³/day. These are the very smallest STWs, serving a population of less than c.400 people.

This flow has been through the full treatment process to be returned to the environment. It's tested to ensure it meets requirements set by the Environment Agency. TDV isn't a measure of storm discharges, that is a different process, measured by event duration monitors (EDM) and is reported separately.

TDV data is usually updated by April, with data from the previous calendar year.

How to integrate our data

We're excited about the possibilities that open data provides for our customers and the water industry. We want to lead the way, so we've set up an application programme interface (API) to connect third parties to our publicly open storm discharge data. Our API can be used to integrate our data into your application.

Find out about our third party API.

Get in touch

If you have any queries or concerns about storm discharge and flow data, contact us using our enquiry form.