Event Duration Monitoring
2021 EDM data
Rivers transform the communities around them and we know that, as a water company, there is more we need to do to take a leading role in making all our rivers the healthiest they can be.
Our Get River Positive commitments are underpinned by five key pledges that pave the way for the restoration and revitalisation of the region’s rivers. We’ve listened to you, our customers, local communities and campaign groups and have committed to five pledges that lead the charge in protecting and revitalising rivers. We want everyone in our region to hold us to account, we will publish clear measurements for success, and we will be reporting back on progress regularly.
Our 2021 Event Duration Monitoring data
We’ve published our Event Duration Monitoring (EDM) data for 2021. This data is released on an annual basis and contains all the monitoring activity at storm overflows across the Severn Trent region. As part of our recent Get River Positive announcement, we have committed to ensuring we are open and transparent and provide information such as this, on our website and in an easily accessible way.
What is Event Duration Monitoring?
Storm overflows are vital in protecting people from flooding and are widely used across the UK and Europe. We fully understand the concern around them and the impact they can have on rivers. We use monitors on our storm overflows to understand the performance of our sites and undertake required action. This is called Event Duration Monitoring (EDM).
Our monitors take readings of the water level either every 2 minutes or every 15 minutes depending on the classification of the receiving watercourse, which is jointly agreed between Severn Trent and the Environment Agency. Every data point captured at or above the overflow level would count towards the total time that a discharge was occurring at that location.
What the 2021 data tells us about our progress
The 2021 EDM data shows that our pledge to reduce spills from storm overflows to an average of 20 per year by 2025 - as part of our Get River Positive commitments - is firmly on track.
Compared to the 2020 annual return, we now have more monitors, and therefore more data, than ever before and will have 100% of monitors installed by the end of 2022. We have committed to provide the information people want and need to see by the end of this year, and so, as well as the name and permit numbers for each overflow location, we now also have additional information about the receiving watercourses and national grid references for each discharge point - allowing you to easily locate every discharge point.
2021 EDM data
We are now monitoring a total of 2,437 sites (92%), compared to 2,288 sites in 2020.
On average, our overflows were operating for 2.2% of the total year in 2021.
On average, spill duration per site has reduced by 1.3 hours in 2021, compared to 2020.
| Year | Total number of spills | Total hours of spills | Average number of spills |
|---|---|---|---|
| 2020 | 60,998 | 558,605.6 | 27 |
| 2021 | 59,676 | 461,127.69 | 25 |
This data pertains to the monitors operational in the year
The above shows we are already making encouraging progress towards our 2030 Get River Positive targets. By 2030, we will ensure our operations will not be the reason for unhealthy rivers and following discussions with NGOs on what good looks like, we will reduce spills from storm overflows to an average of 20 per year by 2025.
Improvements made in the past 12 months and what we are continuing to do:
- The 2021 EDM data shows that our long-term ambition to reduce the use of storm overflows to an average of 20 per year by 2025 is firmly on track.
- We are investing £100m a year on our sewage network, improving our sewer systems, reducing sewer flooding and pollutions, raising weirs and installing more monitoring capability;
- We’re increasing sewer capacity and natural catchment drainage through SUDS (sustainable urban drainage systems) which helps to slow the flow of water during wet weather, so overflows are less likely to be triggered;
- We are continuing to install monitors at all of our storm overflows and sewage treatment works. These help us assess performance and make improvements. Currently, as of March 2022, 92% of our sites have monitors and we’re working flat out to get 100% installed by the end of 2022.