Summary of site:
Turloughs are temporary lakes with no evident inflow or outlet. The water level in the lakes is determined by the local water table, i.e. the level below which the rock is completely saturated (with all pore and other spaces filled). In dry weather the water table falls and the turloughs dry out, only to fill again after heavy rains as a higher level, above the lake bed, is restored. They tend to form in limestone areas and, in this case, the bedrock is the Ballyshannon Limestone, of Carboniferous age.
About 700m slightly west of north of Fardrum Lough there is a closed depression containing a turlough less than 100m long when full.