Llyn Conwy - Water Quality and Soil

Water Quality and Soil

Llyn Conwy is owned by the National Trust and, whilst a natural lake, is managed as a reservoir by Welsh Water.

It supplies some of the water needs of the upper Conwy Valley, including Betws-y-coed and Llanrwst. Contingency plans for drought also name Llyn Conwy as the secondary source in the zone which, along with its own supply area, can feed part of the ‘normal’ Llyn Cowlyd (near Trefriw) supply area. A compensation discharge of 0.91 Ml/d would be required from Llyn Conwy.

The pH level of the lake is reported as pH 7.5257 on average, with calcium carbonate rates at 53.7 mg/l, hardness 3 °GH, free chlorine at 0.2853 mg/l and total chlorine at 0.354 mg/l.

In 2008 the National Trust reported that it was working with its tenant farmers to improve water storage in the Welsh uplands. In this area staff are starting to restore the Migneint blanket bog. Drainage ditches are being blocked to help retain water, to reduce erosion, and to cut the amount of peat entering water courses. Work on the wider Ysbyty Estate aims to improve the quality of drinking water from the lake without the need for expensive treatment works, and to retain the Migneint as one of the largest carbon stores in Wales. Peatland restoration can help enhance wildlife habitats and restore species diversity.

This area is very affected by acid rain and the thin peaty soil is best suited for sheep grazing.

Blanket mire is particularly sensitive to climate change and this location has consequently been used on a number of occasions for scientific research.