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Area of Outstanding Natural Beauty

Llyn - Live Sewage

Polluted by sewage 5,383 hours in 2026 so far..

© OpenStreetMap contributors
Contains OS Data © Crown copyright & database right 2021-2024
© Top of the Poops 2021-2024

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Totals for 2026

Sewage5,383 hours
Monitoring offline0 hours
Potential pollution0 hours
Storm overflows13

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Daily Data - when it rained, and when they spilled

Square = rainfall none → heavy
Drop = sewage minutes → all day
Potential pollution Monitoring offline
Jan - 1,071 hours
Feb - 2,001 hours
Mar - 1,187 hours
Apr - 781 hours
May - 148 hours
Jun - 0 hours
Jul - 0 hours
Aug - 47 hours
Sept - 108 hours
Oct - 38 hours

Storm overflows in and around Llyn

Company Site Name Receiving Waterway Overflow Days Total Duration (hours) Offline/Potential Pollution
Dwr Cymru Welsh Water Llanaelhaearn WwTW Overflow Unnamed Watercourse 167 2,539h 40m -
Dwr Cymru Welsh Water Llithfaen WwTW Storm Overflow Rhyd Hir 63 960h 43m -
Dwr Cymru Welsh Water Trefor WwTW Relief Discharge Point Storm Overflow Unnamed Watercourse 91 891h 21m -
Dwr Cymru Welsh Water Nefyn Storm Overflow Caernarfon Bay 70 753h 42m -
Dwr Cymru Welsh Water Lôn Goch Edern Storm Overflow Afon Geirch 24 136h 15m -
Dwr Cymru Welsh Water Nefyn WwTW Settled Storm Overflow Unnamed Tributary of Afon Geirch 13 53h 22m -
Dwr Cymru Welsh Water Clynnog Fawr Storm Overflow Unnamed Stream 18 25h 58m -
Dwr Cymru Welsh Water Aberdesach Storm Overflow Afon Desach 21 17h 54m -
Dwr Cymru Welsh Water Aberdaron WwTW Storm Overflow Afon Cylch-y-Felin 2 2h -
Dwr Cymru Welsh Water Llanbedrog Long Nant-Iago Storm Overflow Tremadog Bay 2 1h -
Dwr Cymru Welsh Water Aberdaron Storm Overflow Afon Daron 2 1h -
Dwr Cymru Welsh Water Trefor Storm Overflow Unnamed Stream 1 0h 15m -
Dwr Cymru Welsh Water Abersoch Harbour Storm Overflow Afon Soch Estuary 0 0h -

Data Sources & Accuracy

EDM (Event Duration Monitoring) data and Consented Discharges to Controlled Waters with Conditions from Environment Agency & Data Map Wales, and Scottish Water

Experimental derived data from Thames Water API, Some data may be missing or inaccurate. Live sewage data from Stream Water API

Annual figures up to and including 2025 come from official water company returns. The 2026 figure is our own estimate, derived continuously from the companies' live data feeds.

Uses Environment Agency rainfall data from the real-time data API (Beta) - Rainfall data is delayed by up to two days.

This website is intended to provide an accurate representation of the Environment Agency data. The data is hard to use, and thus some errors may have been made. If you find something that is incorrect, please raise an issue at the GitHub issues page and we'll endeavour to fix it quickly.

This project is not associated, approved or endorsed by any of the companies whose logos you see here.