Strikes me that the common link is the Caledonian Canal, so let's look at the well known rivers in the system:
It cannot be the River Ness as it flows out to the Beauly Firth as a river in its own right and does not feed the Caledonian Canal with water, although Loch Ness does form part of the canal.
It cannot be the River Lochy as it flows into Loch Linnhe as a river in it own right and does not feed the canal with water although Loch Lochy does form part of the canal.
As the canal draws its principal water supply from the lochs that make up the system (Lochy, Oich, Ness and Dochfour) a reasonable argument would be that it's one of the rivers that feed into Loch Ness, Loch Oich or Loch Lochy..... but it cannot be one of the rivers that feeds Loch Ness as water from the canal comes
down into Loch Ness at Fort Augustus via the lock system.
That also neatly excludes Loch Lochy which means it can only be a river that feeds water into the canal system at the canals
highest point above sea level and one where, potentially, water could go either SW to Fort William or NE to Inverness.
So that means it can only be the River Garry that feeds Loch Oich as Loch Oich is the highest point in the canal system.
H
