Dwr Cymru Welsh Water

Welsh Water — serves 3 million people across most of Wales and parts of Herefordshire. Major rivers: Wye, Usk, Tawe, Teifi, Conwy. Regulated by Natural Resources Wales rather than the Environment Agency.

Dwr Cymru Welsh Water operates 2,336 monitored storm overflows. 7 are currently spilling. In the last 30 days the network has discharged a cumulative 106.3 years across 9,608 events on average. The Truth Engine has 452 open flags against them right now.

📍 View on national map →📄 Download Truth Report (PDF)⬇ Overflows · CSV

2,336

Storm overflows

Active right now

Monitors offline

452

Open flags

2,402

Spills · last 7 days

106.3 years

Cumulative discharge · 30 days

3 days

Avg event length · 30 days

293

Spills · last 24 hours

Spill record· last 12 months · network-wide

21,969

spill events

+70768% vs prior 12m

1,756,546h

cumulative discharge

+11164981% vs prior 12m

6 weeks

longest single event (all time)

2025-05-09

first event on record

Across 10 water companies in the EA dataset, Dwr Cymru Welsh Water averaged 398.8h per monitored overflow in the last 30 days. The national median was 107.8h per overflow. ranked 10 of 10 of UK water companies by 30-day spill hours per monitored overflow.

Most-discharged-into watercourses

The 12 watercourses with the most Dwr Cymru Welsh Water overflows discharging into them.

River Dee56 overflows
River Taff54 overflows
Afon Lwyd46 overflows
River Wye45 overflows
River Cynon43 overflows
Unnamed Watercourse41 overflows
River Ebbw38 overflows
River Teifi37 overflows
River Rhymni37 overflows
Menai Strait36 overflows
River Tawe33 overflows
Sirhowy River28 overflows

Dwr Cymru Welsh Water

Spill record· last 12 months · network-wide

Most-discharged-into watercourses

Currently spilling· 7

Nant Cledlyn

Henllan Brook

Nant Aeron

Swansea Bay

Afon Twrch

River Dulais

River Machno

Truth Engine flags against Dwr Cymru Welsh Water· 25 open