About Llyn Mawr Nature Reserve
Llyn Mawr is one of three lakes within a Site of Special Scientific Interest, high up on the moorland plateau above the Carno Valley. The reserve comprises the 7.7ha (19 acre) lake itself and a narrow margin of surrounding land adding a further 4.4ha (11 acres).
It is an important site for wildlife conservation of aquatic plants and of bird life in both summer and winter. Visits by the public are welcome but please keep to the southern shore and do not attempt to walk right around the lake. The lake is described as mesotrophic - having a moderate amount of nutrient in the water, derived from the surrounding moorland. It therefore has a relatively rich growth of plants and a correspondingly large number of animals.
In the winter the lake is a popular roost with a number of waterfowl. Ducks such as pochard, wigeon, goldeneye, and the fish-eating goosander come here along with whooper swans - migrants coming south to escape the Arctic winter.
There is an extensive network of bridleways that give access over the moorland and rough grazing of Mynydd Cerrigllwydian, one of which passes Llyntarw, another of the trio of Caersws lakes. This is good curlew country as well as offering hunting grounds for birds of prey including buzzard, kestrel and occasionally merlin and hen-harrier.
Access is limited to one small area of the lakeshore. Short area of boardwalk, other ground can be wet, muddy & uneven.