3 gauges from Cwmafan River Station to Greenpark Weir. The 1 that can be compared with a typical high is not above it. 3 storm overflows upstream are discharging now. Gauges in Neath Port Talbot; levels are checked every 15 minutes.
Stations are listed from source to mouth as the water flows, traced on the river map (OS Open Rivers) and the Environment Agency’s own links between its gauges. A distance “by river” is along the river, and is shown only where the map traces the path.
Streams and rivers with a gauge whose water joins the Afan above one of its gauges, from the source down. Named streams without a gauge that have a page here are listed at the end.
No gauged tributary joins the Afan above Greenpark Weir on the river map. Streams without a gauge are not counted here.
Where the Afan goes
No gauge below Greenpark Weir is known on the river map.
Named streams on the river map that flow into the Afan and have no gauge of their own. Each has a page with what is known about it: the next gauge downstream, and any storm overflows or water-sampling points placed on it.
Afon Corrwg (joins about 9.7 km above Cwmafan River Station)
Nant Cwm-clais (joins about 160 m above Marcroft Weir River Station)
21 storm overflows are traced upstream of Greenpark Weir, the Afan’s lowest gauge on the river map: on the Afan itself, on its gauged tributaries, and on smaller streams that join above there.
3 report discharging now
18 not discharging
0 offline or silent: 0 monitor offline, 0 status unknown, 0 no live feed
Official figures for 2025, for the overflows traced upstream of Greenpark Weir: 1,113 spills over 5,843 hours in total, across all 21.
Each overflow is listed in the stretch above the first gauge its water reaches, from the source down, as on the Gauges tab. A stretch of the Afan includes the smaller streams that join it there.
Above Cwmafan River Station, the Afan’s highest gauge13 overflows · 2 discharging now
Blaengwynfi Tunnel Storm OverflowNot discharging Dwr Cymru Welsh Water · into River Afan · 13.0 km by river above Cwmafan River Station · 2025: 16 spills, 13 h
Glyncorrwg Storm OverflowNot discharging Dwr Cymru Welsh Water · into Afon Corrwg · 12.5 km by river above Cwmafan River Station · 2025: 73 spills, 286 h
Alder Terrace Storm OverflowNot discharging Dwr Cymru Welsh Water · into River Afan · 10.4 km by river above Cwmafan River Station · 2025: 42 spills, 79 h
Cymmer Storm OverflowNot discharging Dwr Cymru Welsh Water · into River Afan · 9.7 km by river above Cwmafan River Station · 2025: 123 spills, 658 h
Upper Cymmer Margam Street Storm OverflowNot discharging Dwr Cymru Welsh Water · into River Afan · 9.7 km by river above Cwmafan River Station · 2025: 27 spills, 14 h
Abercregan Storm OverflowNot discharging Dwr Cymru Welsh Water · into River Afan · 8.2 km by river above Cwmafan River Station · 2025: 64 spills, 1,066 h
Duffryn Afan Road Storm OverflowNot discharging Dwr Cymru Welsh Water · into River Afan · 6.7 km by river above Cwmafan River Station · 2025: 30 spills, 95 h
Cynonville OverflowNot discharging Dwr Cymru Welsh Water · into River Afan · 4.6 km by river above Cwmafan River Station · 2025: 36 spills, 55 h
Ton-Mawr Road Storm OverflowDischarging now since Dwr Cymru Welsh Water · into Afon Pelenna · 4.3 km by river above Cwmafan River Station · 2025: 92 spills, 463 h
Pontrhydyfen Viaduct Storm OverflowNot discharging Dwr Cymru Welsh Water · into River Afan · 1.4 km by river above Cwmafan River Station · 2025: 19 spills, 7.5 h
Pont-Rhyd-Y-Fen Maes-Y-Bettws Storm OverflowDischarging now since Dwr Cymru Welsh Water · into Afon Pelenna · 1.4 km by river above Cwmafan River Station · 2025: 59 spills, 104 h
Pwll Y Glaw Cwmafan OverflowNot discharging Dwr Cymru Welsh Water · into River Afan · 340 m by river above Cwmafan River Station · 2025: 14 spills, 10 h
Between Cwmafan River Station and Marcroft Weir River Station5 overflows
Gwaun Afan Storm OverflowNot discharging Dwr Cymru Welsh Water · into River Afan · 2.5 km by river above Marcroft Weir River Station · 2025: 91 spills, 565 h
London Close Cwmafan OverflowNot discharging Dwr Cymru Welsh Water · into River Afan · 1.2 km by river above Marcroft Weir River Station · 2025: 91 spills, 745 h
London Terrace Cwmafan Storm OverflowNot discharging Dwr Cymru Welsh Water · into River Afan · 1.2 km by river above Marcroft Weir River Station · 2025: 47 spills, 126 h
Cwmavon Road Cwmafan Storm OverflowNot discharging Dwr Cymru Welsh Water · into Nant Cwm - Clais · 670 m by river above Marcroft Weir River Station · 2025: 85 spills, 480 h
Between Marcroft Weir River Station and Greenpark Weir3 overflows · 1 discharging now
Ynys Y Gored Storm OverflowDischarging now since Dwr Cymru Welsh Water · into River Afan · 1.8 km by river above Greenpark Weir · 2025: 53 spills, 145 h
Ynys Street Storm OverflowNot discharging Dwr Cymru Welsh Water · into River Afan · 1.4 km by river above Greenpark Weir · 2025: 54 spills, 305 h
Afan Street Port Talbot Storm OverflowNot discharging Dwr Cymru Welsh Water · into River Afan · 1.0 km by river above Greenpark Weir · 2025: 27 spills, 17 h
Near these gauges, connection not known
Within 3 km of one of the Afan’s gauges in a straight line, but the river map cannot say whether their water reaches it.
Afan Way Storm OverflowNot dischargingbathing water Dwr Cymru Welsh Water · into River Afan · 180 m from Greenpark Weir in a straight line · discharges into a tidal reach, where the water moves both ways · 2025: 38 spills, 83 h
Newbridge Road No 2 Port Talbot Storm OverflowNot dischargingbathing water Dwr Cymru Welsh Water · into River Afan · 490 m from Greenpark Weir in a straight line · discharges into a tidal reach, where the water moves both ways · 2025: 43 spills, 414 h
Wildbrook Estate Storm OverflowNot discharging Dwr Cymru Welsh Water · into Arnallt Brook · 1.4 km from Marcroft Weir River Station in a straight line · its recorded watercourse is not the one mapped beside it · no official annual figure
Conduit Street Port Talbot Storm OverflowNot discharging Dwr Cymru Welsh Water · into Ffrwd Wyllt · 1.5 km from Greenpark Weir in a straight line · its water cannot be followed on the map · 2025: 35 spills, 191 h
Steel Works Port Talbot Storm OverflowNot discharging Dwr Cymru Welsh Water · into Swansea Bay · 1.9 km from Greenpark Weir in a straight line · discharges to the sea, an estuary or tidal water · 2025: 10 spills, 40 h
Duke Street Margam Storm OverflowMonitor offline Dwr Cymru Welsh Water · into Arnallt Brook · 2.0 km from Greenpark Weir in a straight line · its water cannot be followed on the map · 2025: 34 spills, 213 h
Bryngyrnos Storm OverflowNot discharging Dwr Cymru Welsh Water · into Ffrwd Wyllt · 2.1 km from Cwmafan River Station in a straight line · its water cannot be followed on the map · 2025: 100 spills, 352 h
Margam PS Prince Street OverflowNot discharging Dwr Cymru Welsh Water · into Culverted Section Of Arnallt Brook · 2.2 km from Greenpark Weir in a straight line · its water cannot be followed on the map · 2025: 0 spills, 0 h
Afan WwTW Storm OverflowDischarging now since Dwr Cymru Welsh Water · into Swansea Bay · 2.6 km from Greenpark Weir in a straight line · discharges to the sea, an estuary or tidal water · 2025: 74 spills, 968 h
Stallcourt Close Rear Storm OverflowNot discharging Dwr Cymru Welsh Water · into Arnallt Brook Culvert (To Swansea Bay) · 2.6 km from Greenpark Weir in a straight line · discharges to the sea, an estuary or tidal water · 2025: 1 spill, 0.3 h
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