Event Duration Monitoring - Storm Overflows - 2025 (England and Wales)

This Event Duration Monitoring dataset relates to overflow performance in England and Wales. Water and Sewerage Companies (WaSCs) submit this regulatory return annually to the Environment Agency or Natural Resources Wales to meet discharge conditions outlined in the Environmental Permitting Regulations. The English data were downloaded from environment.data.gov.uk (accessed 26th March 2026). Sewer Storm Overflow EDM Annual Returns Data for Wales were downloaded from the Dŵr Cymru/ Welsh Water and Hafren Dyfrdwy websites. For England, 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. What doesn't this dataset show? There are a significant but unknown number of overflows which are not included in this dataset because the WASCs and the Environment Agency don't know where they are within the sewer network. If you spot signs of sewage pollution please report this to the Environment Agency on 0800 80 70 60 or Natural Resources Wales on 0300 065 3000 so that these unmapped discharges can be pinpointed. Emergency overflows in England and Wales are not included in this dataset as the Environment Agency and Natural Resources Wales only require storm overflows to be included in the EDM returns, though some WASCs do record this information. Emergency overflows do have permits but these are for use in the event of mechanical issues, for example pump failure. We do publish the emergency overflows for England and Wales in the consented discharges dataset, but we don't have spill duration data for them. You can find out more about environmental permits for storm and emergency overflows for England here and Wales here. Quality Control The Rivers Trust has endeavoured to clean, check and interpret the data, but cannot be held responsible for any missing or inaccurate data. Points in the sea may be long-sea outfalls or they may be errors in the data. Water companies, citizen scientists and map users are welcome to contact us to notify any known data errors on specific overflows and we will flag these in the map popups and pass on to the regulators. We are providing feedback to the Defra storm overflows taskforce about how to improve transparency around sewer storm overflows, and would welcome feedback and suggestions. Contact us at [e-mail]本数据集为事件时长监测（Event Duration Monitoring，以下简称EDM）数据集，聚焦英格兰与威尔士的溢流性能表现。供水与污水处理公司（Water and Sewerage Companies，以下简称WaSCs）需每年向英格兰环境署（Environment Agency）或威尔士自然资源署（Natural Resources Wales）提交此合规申报材料，以满足《环境许可条例》（Environmental Permitting Regulations）规定的排放要求。 英格兰地区的相关数据下载自environment.data.gov.uk（访问时间：2026年3月26日）；威尔士地区的下水道暴雨溢流EDM年度申报数据，则下载自Dŵr Cymru/威尔士水务与Hafren Dyfrdwy官方网站。 针对英格兰地区的数据集，还补充说明了两类情形：一是事件时长监测设备为何仅能覆盖相关申报周期内不足90%的有效时长，二是该周期内溢流事件为何会出现高溢流频次。 ### 本数据集未涵盖的内容 存在数量可观但无法精确统计的溢流事件未被纳入本数据集，原因在于WaSCs与英格兰环境署无法确定这些溢流点在污水管网中的具体位置。若您发现污水污染迹象，请拨打英格兰环境署热线0800 80 70 60或威尔士自然资源署热线0300 065 3000进行举报，以便精准定位这些未被标注的排放点。 英格兰与威尔士的应急溢流事件未被纳入本数据集：尽管部分WaSCs会记录此类信息，但英格兰环境署与威尔士自然资源署仅要求将暴雨溢流事件纳入EDM年度申报材料。应急溢流事件同样持有排放许可，但其许可仅适用于机械故障（如水泵故障）等紧急场景。我们已在获批排放数据集（consented discharges dataset）中发布了英格兰与威尔士的应急溢流数据，但暂未提供此类溢流事件的持续时长数据。您可通过此处了解英格兰暴雨与应急溢流的环境许可要求，此处了解威尔士相关要求。 ### 质量控制说明 河流保护信托基金（The Rivers Trust）已尽力对数据开展清洗、核查与解读工作，但不对任何缺失或不准确的数据承担责任。位于海域的数据点可能为远海排放口，也可能属于数据录入错误。欢迎水务公司、公民科学爱好者及地图使用者联系我们，告知特定溢流点的已知数据错误，我们将在地图弹窗中标记此类问题，并将相关信息反馈给监管机构。 我们正就提升下水道暴雨溢流透明度的改进方案，向英国环境、食品与农村事务部（Department for Environment, Food and Rural Affairs，简称Defra）暴雨溢流专项工作组提供反馈，同时也期待各界提出宝贵意见与建议。您可通过[e-mail]与我们取得联系。