Tucked away, North of Llyn y Dywarchen, contouring around Clogwyn y Garreg, now lies a strip of marsh lands. Older maps, dating back to the nineteenth century also show a similar site of marsh lands at Bwlch y Moch, but as recently as 1962 – Ordnance Survey maps showes a lake at Bwlch y Moch – Llyn Bwlch y Moch.
The secret to this mysterious lake, can be found if you examine the head and foot of Llyn y Dywarchen, you can see that man is responsible for the lake. Llyn y Dywarchen rests at the natural watershed between Llyn Cwellyn and Llyn Nantlle.
From different books and articles I’ve read – it sounds like the marsh lands which are now Llyn Bwlch y Moch was the natural soak away for Llyn y Dywarchen, which took the water down the Nantlle Valley – flowing mightily on the Afon Llyfni into Llyn Nantlle below.
Then, two damns were built on Llyn y Dywarchen, closing the flow altogether into Cwm Bwlch y Moch – which raised the water level at Llyn y Dywarchen. With the exit into Llyn Bwlch y Moch closed, the flow changed direction into the Cwellyn system, through an artificial water channel – which altered the direction to which it used to flow, which is now South to Llyn y Gadair, just by Rhyd Ddu.
By the North head damn of Llyn y Dywarchen, lies a ruin of an old cottage and some weathered looking Sycamore trees – which could be the reason to the naming of the Cwm (cirque) – as the ruined cottage’s outhouse has a wall with a low aperture, which suggests that Pigs might once have been living here? (Moch = Pigs in Welsh) Another reason might be that Clogwyn-y-Garreg, the crag that overlooks the Cwm looks like the profile of a Pig when viewed from Cwm Nantlle below? Or it might refer to our Welsh prose stories, Mabinogion, where a boar guides Gwydion to Nantlle in search of Lleu?
At the Northern foot of the lake, there’s evidence that the lake once was very important in supplying the old copper-works located below in Drws y Coed, as there is a great stone damn. (Evident in the first picture as a straight line at the end of the Â lake)Â The center of the damn has now been dismantled, to ensure that the lake doesn’t fill up again, which is a shame, as I think this peaceful spot, hidden away from the road would be a fantastic stretch of water.
So, this damn explains why the first Ordnance Survey maps didn’t show any lake at this spot – the lake only existed after the damn was build in around 1840 – to serve the copper mines below, and was still a lake according to the Ordnance Survey maps until 1962, long after the closure of the mines, and after breaching the damn again, sometime after 1962, the lake was drained again, and left to be the marsh lands that we see today.
Dad knows the farmer that lives in the farm directly below the damn, he’s going to enquire more from the farmer about the lake and it’s history for me, so I shall update this page in the future!
Tags: 1962 Ordnance Survey, Afon Llyfni, Clogwyn y Garreg, Copper Mines, Copper Mines Drws y Coed, Cwellyn, Cwm Bwlch y moch, Cwm Bwlch y Moch History, Drws y Coed, Gwydion, Lleu, Llyn Bwlch y Moch, Llyn Cwellyn, Llyn Dywarchen, Llyn Nantlle, Llyn y Dywarchen, Llyn y Dywarchen dam, Llyn y Gadair, Mabinogion, Nantlle Valley, Rhyd Ddu