North of the Great Glen only the River Conon has a larger catchment area than the 270 square miles of the Beauly system. The source of the Beauly is the River Glass which rises as the River Affric to the west of Loch Affric between the mountains of Mam Soul and Ben Arrow not far from Dornie on the west coast. The Affric generally flows in a northeasterly direction to Loch Affric and from the outflow of the loch a short distance down Glen Affric to Loch Beinn a Mheadhoin.
Below the dam the Affric flows down the upper Strathglass, over Dog Falls to be joined from the right bank by the Abhain Deabhag/Tomich Burn one mile above the Fasnakyle Power Station. The Tomich Burn which drains an area to the south of Loch Beinn a Mheadhoin is a very important spawning area for the whole system, however fish can only ascend the burn for three miles as the Plodda Falls deny them further progress.
From the confluence of the River Affric/Tomic Burn the river becomes the Glass and its flow is enhanced by the River Cannich which joins the river one mile below the Fasnakyle Power Station at the village of Cannich. From Cannich the river flows through the scenic Strathglass for some 9 miles to Struy, where it is joined by the River Farrar downstream of the Struy road bridge. It is from this point that the river becomes the Beauly.
From the Junction Pool at the mouth of the Farrar, the Beauly continues to flow down Strathglass and soon enters a steep gorge section and the large deep pools above the Aigas and Kilmorack Hydro system. Below Kilmorack Dam/Power Station the river flows through rich farm/pastureland to Lovat Bridge, then past the town of Beauly to the tidal waters of the Beauly Firth.
Hydro Electric Scheme
In the mid 1950s the North of Scotland Hydro Electric Board harnessed the river system. The first section was planned with great care to preserve the scenic beauty of Glen Affric. Initially two large dams were constructed, one in Glen Cannich at the eastern end of Loch Mullardoch at the head of the River Cannich and a second one in a gorge below Loch Beinn a Mheadhoin in Glen Affric. Water from Loch Mullardoch is piped to the Mullardoch power station, then to Beinn a Mheadhoin and the Fasnakyle power station. Neither of these dams have fish passes as they were constructed in sections of their respective rivers that migratory fish could not reach due to natural barriers. In order to preserve Loch Beinn a Mheadhoin's beautiful surroundings, the level of the loch is not allowed to fluctuate greatly and Loch Affric is unaffected by these works.
The second phase was the harnessing of the rivers Farrar and Beauly. Loch Monar was dammed at the head of the River Farrar and water piped to the power station at Deanie above Loch Beannacharan. This loch was also dammed and water is piped to the power station at Culligran. Finally two dams/power stations were built in the gorge section of the Beauly at Aigas and Kilmorack. The dams at Beannacharan, Aigas and Kilmorack have Borland fish lifts and river levels are maintained by compensation water.