Where does the river dee source from. the one in chester u.k.?

Llyn Tegid (Bala Lake) is the largest natural lake in Wales. It is a Site of Special Scientific Interest and attracts many different kinds of birds. The unique Gwyniad, a fish left over from the Ice Age, is found only in Llyn Tegid. Y Bala means the outlet, describing the exit of the River Dee from Bala Lake, before its journey through the Dee Valley.