In practice, clearing of rocks from the river channel where it exited Loch Garry and the fitting of a sluice to control the outflow from Lock Quoich were the main modifications made to the waterway by the canal commissioners.

The river flows either side of an island called Eilean Dubh, and on the northern channel there is a small dam and Quoich power station.

It was designed to prevent salmon moving further upstream, because their former spawning grounds were destroyed when the level of Loch Quoich was raised by over 100 feet (30 m).

It was completed early in the construction programme to allow smolts in the upper river to move downstream before the dam was closed.

[5] About one quarter of the distance along its length, it is crossed by a bridge carrying a track to Torr na Carraidh, a hill on its southern shore that rises to 404 feet (123 m).

[7] The dam includes a Borland-type fish pass, which works in a similar way to a canal lock, enabling salmon to access Loch Garry.

[8] Immediately downstream of the dam is a category C listed suspension footbridge, designed by the engineers Speirs and Company of Glasgow, and dating from the late 19th century.

[9] White Bridge is a little further downstream, and as the river enters the village of Invergarry, the only substantial settlement along its course, it is joined by Aldernaig Burn, flowing southwards from Loch Lundie, and is crossed by a category B listed bowstring suspension footbridge with a wooden deck.

[10] The bridge is an early steel design which spans 197 feet (60 m), but by 2009 some of the main trusses were sufficiently corroded that it was closed for safety reasons.

[12] Prior to its construction and the re-alignment of the A82, the road crossed the river further downstream on a single span bridge dating from the early 19th century.

It was promoted by a private company, and would have involved diverting the water to the west coast, rather than allowing it to continue flowing eastwards to the Great Glen.

The architect James Shearer ensured that the buildings blended into the landscape in an era where people were increasingly concerned about the impact of construction schemes on the scenery.

At the bottom of the spillway, it is shaped like a ski jump, so that water cascading down the slope rises up into the air and falls into the river as spray, some distance from the foundations of the dam.

[8] The River Garry runs through an area which experiences some of the highest amounts of rainfall in Scotland, and this has contributed to its importance both for the operation of the Caledonian Canal and later for the production of hydro electric power.

[20] The river is around 14.5 miles (23.3 km) long from the outfall at Loch Quoich to the month at Invergarry,[21] and runs through Glen Garry, which is located in the Caol and Mallaig ward of the Highlands.

During that period, sheep farming became the main source of employment within the Glen, with forestry also important, as large quantities of wood were needed for the building of the Caledonian Canal.

[23] Residents of the Glen traditionally spoke Gaelic, but use of the language has declined, as a result of emigration, immigration by sheep farmers, and English and Welsh people moving into the area in the early 2000s.

[27] A comprehensive study was carried out in the 2010s into the effects of the dams on fish stocks in the river, particularly salmon, where numbers had dropped by a factor of more than ten between 1956 and 2019.

As a result of increased water levels in the lochs following construction of the dams, some 40 percent of the salmon habitat had been destroyed, and what was left had often been changed.

No spawning fish or juveniles were found in the Gearr Garry, below the Quoich dam, and factors affecting the salmon included changes to the chemistry and temperature of the compensation water, which was released from the bottom of the reservoir, issues arising from the fish trap near Quoich power station, the presence of invasive pike and minnows, and interbreeding between wild and farmed salmon.

The fish trap was installed to collect eggs for rearing in a hatchery, initially at Invergarry but subsequently next to Quoich power station.

[32] Improvements to enable salmon to access the river will probably also benefit other species which move between the sea and fresh water habitats, such as lampreys and eels.

The river has resident populations of fresh water fish including brown trout and Arctic char, which have suffered decline since the hydro-electric schemes altered their habitat.