Event Duration Monitoring - Storm Overflows - Annual Returns

This Event Duration Monitoring dataset relates to the performance of storm overflows in England. Data are provided by Water and Sewerage Companies (WaSCs) to the Environment Agency each year as part of their regulatory Annual Return, to fulfil their permitted conditions to discharge from these storm overflows under the Environmental Permitting Regulations. Data files are provided by year (one for 2020, one for 2021) and include a sheet for each of the 10 WaSCs with storm overflows in England. Each WaSC sheet shows how often and how long each monitored storm overflow discharged during that year. From 2021 onwards the dataset also includes reasons why event duration monitors may have provided information for <90% of the relevant return period, and why an overflow may have high spill counts in that period. These data reflect the best available information held by the WaSC at time of submission. The data file for each year also contains key summary data. These include: number of storm overflows monitored, number of storm overflows returning spill counts, average spill duration and average spill count for each WaSC. A third data file contains the annual key summary statistics from respective years plus a table showing long-term trends from 2016-2021. Attribution Statement: © Environment Agency copyright and/or database right 2022. All rights reserved.