Important notice

This map provides near real-time information about Dŵr Cymru’s storm overflow activity, as indicated by our event duration monitors.

You can use the map to see if our monitors indicate if a storm overflow is currently operating (as they are designed to do during or following heavy rain) and the date/time of the last recorded instance of them operating. The data received from our monitors isn’t always accurate. It doesn’t confirm if a storm overflow is operating, it only provides an indication.

We want our information to be accessible for water users to be able to make an informed decision before entering or using the water. This should not be considered as advice on bathing water quality. For information on bathing water quality, please refer to Natural Resources Wales’s Bathing Waters pages.

You can find out more about event duration monitoring here.

Storm overflow map

This map provides near real-time information about Dŵr Cymru’s storm overflow activity, as indicated by our event duration monitors.

Please note that this is a beta version of the storm overflow map. We are using this version to continue to test and improve the site.

or you can view the map in a new window.

How to use the map

Each of our storm overflows is represented by an icon. When you click on an icon, a pop up appears which gives information about the operating status of the storm overflow.

What do the different icons mean?
The legend widget on the right-hand side of the map shows the meaning of the different symbols – with the different colours and graphics representing the status of the storm overflow.

There are two types of overflows. Storm overflows are represented by circular icons and overflows are represented by triangular icons. The overflows represented by triangular icons are currently operating as storm overflows but are not designed to do so in the long term. These are currently under review.

There are four types of status for each overflow, with the different graphic infills and colours reflecting the spill status.

Not operating icon  overflow isn't operating 
Operating icon  overflow is operating
Operated in last 24hrs icon  overflow isn’t operating (but has in the past 24 hours)
Maintenance Icon  overflow is under maintenance

Bathing water icon is a pin to a bathing location

How do I find my location on the map?
There are three ways of finding a specific location on the map.

  • You can use the search widget to search for an address or area.
  • You can use the find my location widget (if device settings are enabled) to automatically find and zoom into your location. This feature is very useful if using a mobile device.
  • You can also zoom in and out of the map using the + and - buttons

You can also use the basemap widget to switch to a different basemap (background map) view.

To return to the default map view, click on the home button.

You can use the layers widget to switch on/off different layers such as bathing water areas, just leaving the storm overflow asset info, if required.

How do I know if a storm overflow is operating, or not?
Clicking on the asset pin enables a pop-up. This pop-up contains information about the asset – including whether it is currently operating or not and the date / duration of the last storm overflow event.

About Storm Overflows

What are storm overflows?
You can learn more about storm overflows here.

About Event Duration Monitoring

What is EDM?
EDM stands for Event and Duration Monitoring. We report EDM data for each asset annually to our environmental regulators, following an industry- wide standard called the 12/24 methodology. We also upload our annual data set to our EDM map, on our website. You can read more about EDM here.

Frequently asked questions