YW Night-flow monitoring 2026

Data History Data Origin Companies have configured their networks to be able to continuously monitor night flows using district meters. Flow data is recorded on meters and normally transmitted daily to a data centre. Data is analysed to confirm its validity and used to derive continuous night flow in each monitored area. Data Triage Considerations Data Quality Not all DMAs provide quality data for the purposes of trend analysis. It was decided that water companies should choose 10% of their DMAs to be represented in this data set to begin with. The advice to publishers is to choose those with reliable and consistent telemetry, indicative of genuine low demand during measurement times and not revealing of sensitive night usage patterns. Data Consistency There is a concern that companies measure flow allowance for legitimate night use and/or potential night use differently. To avoid any inconsistency, it was decided that we would share the net flow. Critical National Infrastructure The release of boundary data for district metered areas has been deemed to be revealing of Critical National Infrastructure. Because of this, it has been decided that the data set shall only contain point data from a centroid within the DMA. Data Triage Review Frequency Every 12 months, unless otherwise requested. Data Limitations Some of the flow recorded may be legitimate night-time usage of the network. Some measuring systems automatically infill estimated measurements where none have been received via telemetry. These estimates are based on past flow. The reason for a fluctuation in night flow may not be determined by this dataset but potential causes can include seasonal variation in night-time water usage and mains bursts. Data Publish Frequency Monthly. Supplementary information Below is a curated selection of links for additional reading, which provide a deeper understanding of this dataset. 1. Ofwat – Reporting Guidance https://www.ofwat.gov.uk/wp-content/uploads/2018/03/Reporting-guidance-leakage.pdf 2. Water UK – UK Leakage https://www.water.org.uk/wp-content/uploads/2022/03/Water-UK-A-leakage-Routemap-to-2050.pdf Data Schema DATA_SOURCE: Company that owns the DMA DATE/TIME_STAMP: Date and time of measured net flow DMA_ID: Identity of the district metered area CENTROID_X: DMA centroid X coordinate CENTROID_Y : DMA centroid Y coordinate ACTUAL_MIN_NIGHT_FLOW: The lowest recorded average net flow between 12 and 6am MIN_NIGHT_FLOW : The average flow within the 2-4 am time window UNITS: Measurement of flow