Big Five Agg.
Dŵr Cymru Welsh Water · 👁 41 views
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About the Big Five system
“Big Five Agg.” means the combined storage of Welsh Water’s five major reservoir systems serving the South East Wales Conjunctive Use System (SEWCUS).
It brings together Usk, Talybont, Llandegfedd, the Taf Fawr reservoirs (Llwynon, Cantref and Beacons), and Pontsticill. The level shown is for this combined system. There is no single reservoir location to plot on the map.
Source: Welsh Water’s 2025 Drought Plan, Appendix 2 (SEWCUS).
Level history
This time of year, in past years
| Year | % full (nearest reading) |
|---|---|
| 2024 | 80.2% |
Nearest reading within 10 days either side of today's date, for each year on record.
El Niño 2026–27The tropical Pacific is running 3.2 °C above normal (week of 27 September–3 October 2026).What past El Niño winters brought Britain →
Where this comes from. Reservoir data © the UK water companies, from their published reservoir-level reports and the Stream water-industry open data portal (CC BY 4.0). Thames Water London history via the London Datastore (Open Government Licence v2). Figures are exactly as published by Dŵr Cymru Welsh Water — reporting day and
rounding vary. Levels older than 21 days are marked "last reported" rather than treated as current.