Of glacial origin, Loch Awe is the longest lake in Great Britain with a total length of 41.0 km. It is, however, an extremely narrow lake, and is in most places only about one kilometer in breadth. The mean breadth is only 2.3 percent of the length which is the smallest percentage observed in any of the 562 lakes surveyed until now. The surface area is 38.5 km² which means that Loch Awe is the third largest in Great Britain in this respect. It has a mean depth of 32.0 m, a maximum of 93.6 m and a total volume of 1,230,400,000 m³. Like Loch Lomond there are two main basins deeper than 30 m - one occupying the northern arm (with two separate depressions), the other occupying most of the long axis of the lake from the northern islands south.

The catchment of Loch Awe has a relatively high mean altitude and moderate slopes. Almost 20% of its land is afforested and much of its geology is base-rich.

Same as Loch Lomond and Loch Ness, Loch Awe has been subject to most human interference. The lake is likely to be significantly enriched by the activities of humans in its catchment. But, still now, the allochthonous matter content is not high enough to reduce the oxygen content in water to the considerable extent characteristic. In this lake, however, one of the few notable exceptions to the general similarity in chemical content of surface, depth and outflow waters was the summer increase of silicon with depth which was also observed in Loch Ness (1, 2, 4, 10).