Llyn Conwy

Llyn Conwy (SH780462) is a lake in the county of Conwy in central north Wales. It is the source of the River Conwy which, on flowing south out of the lake, swings round to then generally flow in a northerly direction for a distance of some to its discharge in Conwy Bay. Llyn Conwy lies at a height of about 1,488 ft, with a maximum depth of 16 feet, and is by far the biggest lake of the Migneint moors, an extensive area of blanket mire with high rainfall - about 260 cm p.a.

Geology

This is an area of Ordovician rocks, lending its name to the "Llyn Conwy Formation", which is identified by its yellowish rhyolitic tuffs. This Formation also reappears in Afon Tryweryn to the south-east, where the hard rock was utilized in the construction of Llyn Celyn dam.

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...
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