Llanishen Reservoir
Latest sample 9 Sep 2026: E. coli <10, enterococci <10 per 100 ml.
Classifications and description
The cleanest samples over the last four seasons.
Past years: 2025 Excellent
Llanishen Reservoir to the North of Cardiff opened in 2023 as a recreational site with water activities available on-site include canoeing and kayaking. The site is privately owned and operated by Dwr Cymru Welsh Water. Newly designated as a bathing water in 2025, all open water sessions are supervised, with the access-point to the water via the pontoon onto Llanishen Reservoir. The bathing water sampling point is off the pontoon access point to the designated swimming area. Lisvane & Llanishen Reservoirs are working reservoirs and are primarily used to store and supply water for the CELSA steel plant in Cardiff. The water levels will necessarily fluctuate over time in peak supply periods and with dry weather which may limit water sports activity and access to the bathing water.