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 2,359 monitored storm overflows. 4 are currently spilling. In the last 30 days the network has discharged a cumulative 6.2 years across 3,312 events on average. The Truth Engine has 44 open flags against them right now.

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

2,359

Storm overflows

Active right now

Monitors offline

Open flags

828

Spills · last 7 days

6.2 years

Cumulative discharge · 30 days

21.8 h

Avg event length · 30 days

218

Spills · last 24 hours

Spill record· last 12 months · network-wide

26,313

spill events

+61093% vs prior 12m

5,933,385h

cumulative discharge

+28062206% vs prior 12m

13 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 22.9h per monitored overflow in the last 30 days. The national median was 23.6h per overflow. ranked 5 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 Lwyd47 overflows
River Cynon45 overflows· 1 active
River Wye45 overflows
Unnamed Watercourse41 overflows
River Ebbw39 overflows
River Teifi37 overflows
River Rhymni37 overflows
Menai Strait36 overflows
River Tawe34 overflows
River Usk30 overflows

Dwr Cymru Welsh Water

Spill record· last 12 months · network-wide

Most-discharged-into watercourses

Currently spilling· 4

River Cynon

River Sirhowy

River Gwili

River Machno

Truth Engine flags against Dwr Cymru Welsh Water· 25 open