National River Flow Archive (NRFA) staff Alannah Killeen, Catherine Sefton and the North Wales representative Amulya Chevuturi carried out a two-day field visit to North Wales with Natural Resources Wales (NRW) on Tuesday 5th and Wednesday 6th October 2022.
Hydrometry and telemetry officers from NRW’s North Wales Area took us to visit a number of river flow gauging stations on the Dee and its tributaries, including the Alyn, Ceiriog and Clywedog, as well as the Clwyd, the Glaslyn and its tributary the Colwyn, and the Afon Cerist. We discussed details of the stations, their operation, metadata updates and any upgrades that have been made in order to extend and improve the information provided by the NRFA through our website.
The sites visited included a range of different structures from Crump weirs and flumes to open channel velocity area stations. We were able to see recent improvements to stations, including new eel passes such as at 67025 – Clywedog at Bowling Bank. At this station, a mussel rope is installed March to September to enable eels to pass over the Crump weir more easily. A larger gauging station we visited was the 67015 – Dee at Manley Hall; this station is very important as it is a National Hydrological Monitoring Programme (NHMP) site and therefore the data is included each month’s UKCEH Hydrological Summary. The structure consists of two Crump weirs, one for low and one for high flows and the geology at this site is unusual, as the mudstone and sandstone outcrop can be seen just below the water level on the low flow weir. The flow regime at this station is affected by the Alwiyn, Brenigaonig, Celyn and Tegid reservoirs, and flow is managed to ensure it meets the Habitat Directive requirements. Less impacted but very important is the gauging station we visited on the 65001 - Glaslyn at Beddgelert. This station is used for early flood warnings for the whole catchment and has considerable out of bank flow, as it is flashy catchment. This station is situated in an upland catchment which drains the southern flanks of Snowdonia, and therefore was a very scenic visit! We were even lucky enough to see an otter floating downstream and over the weir at 64011 - Cerist at Llaw'r Cae, which was an extra bonus to the trip!
Such visits allow the NRFA’s staff and Regional Representatives to update their knowledge of current equipment, processes and problems at each site, giving them a better understanding of how the river flows are measured. This information underpins the quality control of data submitted to the archive and allows metadata updates to inform the user community of new and emerging issues which should be considered when analysing NRFA data. The NRFA aims to conduct between two and four measuring authority liaison visits a year across the UK’s 24 regional hydrometric data providers.
Thank you to Natural Resources Wales (NRW) North Wales Area Hydrometry and Telemetry team who hosted the field visit and ensured we visited as many stations as possible in the two days. It proved very useful and will help inform and advance a large number of updates to the archive.