Storm overflow disharge into rivers occurs when sewage treatment works experience maximum capacity volumes, often following heavy rain events. The Event Duration Monitoring dataset for 2020 has now been published here. This relates to the performance of storm overflows, provided by Water and Sewerage Companies for the 2020 regulatory annual return.
The dataset includes 10 (one for each Water and Sewerage Company with storm overflows in England) files describing how often and for how long, monitored storm overflows discharged during 2020.
The Water and Sewerage Companies provide this regulatory return to the Environment Agency each year to fulfil their permitted conditions to discharge from these storm overflows under the Environmental Permitting Regulations.
It is in the format of a downloadable zip file that includes separate spreadsheets for each of the 10 water companies and an additional summary spreadsheet.
The EA have also produced a blog discussing the data which can be found here and there is a video explaination available on the EA’s YouTube channel.