Llyn Trawsfynydd

Llyn Trawsfynydd is a large man-made reservoir situated near the village of Trawsfynydd with a total surface area of 4.8 km² (1,180 acres) the reservoir is slightly more extensive than Wales's largest natural lake, Llyn Tegid (which covers an area of 4.5 km²).

The only inland water close to the A470 created between 1924 and 1928 by building four dams, its purpose was to supply water for Maentwrog hydro-electric power station.

Although two dozen properties, some of historical significance, were lost in the creation of the lake, there was little local objection at the time. Indeed the power station was regarded as a good thing because it was capable of supplying the whole of North Wales' electricity needs. However local landowners and farmers did object to the loss of rights of way across their former lands. In order to negate long detours round the new lake, a small road was built along the western shore and a footbridge was erected across the narrowest part of the lake.

The estuary of the Dwyryd is long and sandy and includes the confluence of the River Glaslyn close to the low water mark.

The whole of the river drains off igneous and ancient rocks of the Cambrian and