Monday 17th August, 2026
Analysis of Welsh river level data by Afonydd Cymru is showing an alarming picture of water heights following the latest heatwave, with many of Natural Resources Wales’s gauging stations now registering lowest recorded levels.
As of today, 28 gauging stations across Wales are registering lowest recorded levels (since the station was built), with a further 46 within 3cm of this mark.
Many of the stations registering the lowest recorded levels are on tributaries. This is bad news for already threatened fish species such as Atlantic salmon and particularly sewin, whose juveniles largely inhabit the smaller streams.
The lower levels mean higher temperatures, lower oxygen levels, increased potential predation on these small fish and the increased chance of streams drying up completely.
Natural Resources Wales gauging station readings on major Welsh rivers as of 17th August 2026. Those in red are the rivers downstream of a gauging station at or below the lowest recorded level for that station. Those in orange are within 3cm of the lowest recorded level. Those shown in blue are more than 3cm higher than their lowest recorded level (although could still be below “normal” flows).
Extra water from reservoirs helping some rivers
The main stems of some Welsh rivers that are supported by reservoirs are showing signs of better flows, which is testament to Natural Resources Wales’s requests for more water to be released by Welsh Water and Hafren Dyfrdwy.
The Dee, for example (river 7 on the map), appears to be within or just below normal levels following extra releases from the four reservoirs that make up the Dee Regulation Scheme.
The main stem of the Tywi (16) is also holding up relatively well in the drought, following Natural Resources Wales-requested releases from Llyn Brianne, as is the upper River Severn (10), which is supported by Clywedog Reservoir and Lake Vyrnwy.
However, two of the Dee’s tributaries that do not receive reservoir water (the Ceiriog and Clywedog) and one of the Tywi’s tributaries (Twrch) are at lowest recorded levels, indicating what the situation for these SAC-designated rivers might be if they had not received the extra water.
Mid and South East Wales
The Usk (21), meanwhile, is not faring well. One of its main stem gauges (at Crickhowell) is at the lowest recorded level, as are two important tributaries: the Senni and Ysgir.
And the situation on the neighbouring Wye (13), which receives extra water from the Elan Dams, is even more concerning. Over 50% of its Natural Resources Wales gauges are at their lowest recorded level, including those on an important upper river tributary, the Irfon.
Anglesey and the North
Another part of Wales of particular concern is Anglesey, where the rivers Rhyd y Valley and Frogwy are at or below lowest recorded levels, as are some gauges on other important North Wales rivers, such as the Gwyrfai (3), Dyfi (9) and Dysynni.
Meanwhile the Seiont (2), one of the few rivers in Wales whose salmon populations have been holding up, is approaching its lowest ever recorded level.
Hafren Dyfrdwy were reporting that Llyn Clywedog, which supports flows in the Severn, was reported to have dropped to just over 50% of capacity last week.
The South and West
Another affected catchment is the Taff (23) in South East Wales. The main stem is low but major tributaries including the Cynon and Rhondda are all registering lowest recorded levels.
West Wales seems to be the area where levels are holding up best, even before the small amount of rain that fell over the weekend.
However, even in this area, sections of the Western Cleddau (17), Taf (18) and Ystwyth (12) are at lowest recorded level or close to it.
Hope of some respite on the horizon?
The weather over the next two weeks is forecasted to be more unsettled with some rain arriving from the west.
For the sake of many rivers across Wales and their fish populations, this break in the dry conditions cannot come soon enough.
Looking further ahead, hotter summers and more prolonged dry periods will become an increasing pressure on our environment. Wales needs to create healthier and more resilient landscapes that retain more water in wet periods to be released slowly into rivers an to give some alleviation to the kind of conditions experienced this July and August.