Event Duration Monitoring (Monthly)

The majority of EDMs use ultrasonic instruments to measure the level in assets connected to storm overflows. An ultrasonic instrument takes a measurement at fixed intervals: either every ten seconds (usually where connected to mains power) or every 120 seconds (often where powered by battery). The EDM will be configured so that, when the level readings are equal to or greater than the level of the storm overflow (known as the set point) the EDM sends a signal to record this activation. For a minority of assets, storm wastewater is pumped to a storm overflow, and in these cases EDMs are configured to record the pump start and pump stop times. Many SWW EDMs record data every ten seconds so very short duration activations can be detected, and are recorded in this dataset. Note that this frequency of monitoring is greater than required by our environmental permits, and so SWW may have more data points (and more activation records) than equivalent datasets from other water companies. This dataset is different to the annual returns provided to, and published by, the Environment Agency, because the Environment Agency requires water companies to report using its 12/24 counting method (see the Environment Agency’s guidance on counting spills: Water companies: environmental permits for storm overflows and emergency overflows - GOV.UK). Prior to publishing this data, SWW has undertaken a verification process to provide confidence in the accuracy of the dataset. As such, data in this dataset may differ from our WaterFit Live system and the National Storm Overflow Hub, which communicate start/stop data in near-real time. SWW will undertake further verification and validation prior to finalising its annual return to the Environment Agency: as such, this dataset may be amended in the future to reflect changes made as a result of further verification processes. This data can also be downloaded in an alternative format from South West Water's website本数据集涉及的多数溢流监测电子设备（Electronic Data Monitor, EDM）采用超声仪器，对与暴雨溢流设施相连的运维资产液位进行测量。超声仪器按照固定间隔采集数据：若设备连接市电供电，采集间隔通常为10秒；若采用电池供电，则通常为120秒。该EDM的配置逻辑为：当液位读数等于或高于暴雨溢流设施的设定点（set point）时，设备将发送信号以记录此次激活事件。针对少数运维资产，风暴污水会被泵送至暴雨溢流设施，此类场景下EDM的配置目标为记录泵启停时刻。西南水务（South West Water, SWW）的多数EDM以10秒间隔记录数据，因此极短时长的激活事件也可被检测并录入本数据集。需说明的是，此监测频率高于本公司环境许可的要求，因此相较于其他水务公司的同类数据集，本数据集拥有更多数据点与激活记录条目。本数据集与提交给环境署（Environment Agency）并由其发布的年度报送数据存在差异：环境署要求水务公司采用其规定的“12/24计数法”进行溢漏计数，具体可参考环境署发布于GOV.UK官网的《水务公司：暴雨溢流与应急溢流环境许可指南》。在发布本数据集前，西南水务已完成验证流程，以确保数据集的准确性。因此，本数据集的数据可能与准实时传输启停数据的WaterFit Live系统及国家暴雨溢流枢纽（National Storm Overflow Hub）所展示的数据存在差异。西南水务在向环境署完成年度报送前，还将开展进一步的验证与确认工作。因此本数据集未来可能会根据进一步验证流程中发现的变更进行修订。用户亦可从西南水务官网下载本数据集的其他格式版本。