How deep is Loch Lomond? And other ‘bonnie banks’ facts

How deep is Loch Lomond is often asked by visitors to the Loch Lomond and Trossachs National Park. At 623ft /190m, it’s the third-deepest loch in Scotland and the largest by surface area. Also answered here: where is Loch Lomond – plus how it was made and how the Romantics discovered it. 

By the way, the loch hasn’t got a monster. But it has an upmarket shopping experience, Loch Lomond Shores, at Balloch.

And if you want to discover a lot of other fascinating and downright wacky facts about this loch, then take a look at our big big page Loch Lomond information. 

However, if you want more information about the setting of the loch or read about the Loch Lomond monster (which doesn’t exist) or the song ‘The Banks of Loch Lomond’ (which certainly does) then keep reading here – it’s all below…

Anyway, settling the question about Loch Lomond’ depth was first addressed by the Hydrographic Department of the Admiralty in Britain, who did the first surveys in the 1860s.

The splendidly named Captain H.C. Otter used a lead-weighted line and a rowing boat for his soundings.

The Royal Society of Edinburgh was an enthusiastic supporter of efforts to find out more about the depth contours of many of Scotland’s lochs.

However, as the 19th century went on, issues arose as to who would fund such a project. The Admiralty was approached and seemed interested at first.

However, it seems that someone in the Treasury in far-off London, England, eventually had a look at a map and pointed out to the Admiralty that Loch Lomond wasn’t actually the sea.

As such, it wasn’t going to have much in the way of battleships floating about in it, so could they please restrict themselves to salt-water surveys on the grounds of cost…?

Loch Lomond from Duncryne Hill
Looking north into the Highlands and over Loch Lomond, from Duncryne Hill.

(Pictured here) This Loch Lomond panorama, looking up the loch from its south end, is a September pic., as you can see by the autumnal rowan berries.

The Highland Boundary Fault runs through the islands in the middle distance. The loch is confined to a deep, narrow trench in the far distance. Closer at hand, you can see how it spreads out in the gentler terrain of the Lowland edge.

Anyway, the experienced oceanographer Sir John Murray took up the cause and went on to create the ground-breaking Bathymetrical Survey of the Fresh-Water Lochs of Scotland, 1897-1909 – a work that still has value today.

This survey is also, presumably, the original source of the oft-quoted other facts about Scottish lochs: such as the water volume of Loch Lomond is 92,805 million cubic ft (second largest in Scotland after Loch Ness); the surface area of Loch Lomond is 27.45 sq miles (largest in Scotland with Loch Ness second) and so on. 

However, there has been an update on our knowledge of the depth of Loch Lomond. Survey work by the British Geological Society in early 2009 found that the north of the loch is a deep trench with very steep sides, the result of glaciation.

What they seldom talk about at Loch Lomond
What they seldom talk about at Loch Lomond. View north from Balloch.

What? Loch Lomond Has A Monster Too? 

As well as sounding out the depth of Loch Lomond, the original Bathymetrical Survey also looked into another phenomenon seen in Loch Lomond as well as other lochs (lakes) right across the globe.

There is an ancient saying about Loch Lomond as having ‘a wave without a wind, a fish without a fin, and a floating island’.

The first part of the old saying may refer to a ‘seiche’ – a scientific term from a Swiss French dialect word.

It now means a standing wave in an enclosed body of water. (Think of it as a ‘slosh’ – that’s the word that’s used for this phenomenon on the North American Great Lakes.)

The key here is that the water body should be enclosed and that the wave is observed irrespective of the weather conditions.

As for the other two parts of the saying, personally, I like to think that the fish without fin is the Loch Lomond monster – that’s the one that never quite caught on in the way that our chum up on Loch Ness did.

Road-signs by Loch Lomond
Road-signs by Loch Lomond – note appearance of Gaelic.

Many years ago, at the peak time for the old Loch Ness monster mania that did so much for tourism in the Scottish Highlands, there was actually a report of a monster on Loch Lomond as well!

In the days of steam, it was apparently seen from the footplate by a train crew.  (I expect it was only a seiche.)

Finally, as for the floating island, if it isn’t a monster hump (and, no, I’m not being serious there at all), then it might be the mats of vegetation that can break off the banks after waves or storms.

The Bonnie, Bonnie Banks of Loch Lomond…

Loch Lomond has been loved to bits, not just because of that well-known song ‘The Banks of Loch Lomond’ (words below) but because of the fact it lies within easy reach of the Clydeside conurbation, the geographer’s phrase for Glasgow and round about.

The area is within the Loch Lomond and Trossachs National Park. Naturally, in an area so beloved of tourists, the ‘infrastructure’ is well developed. There is a good choice of Loch Lomond cruises.

But looking at where Loch Lomond is situated actually explains a lot about how the area gained its status as an icon of Scottish scenery.

And folk in other parts of the world who hear that famous song ‘The Banks of Loch Lomond’ also may wonder where this famous body of water is.

‘The Banks of Loch Lomond’ is an iconic song of Scotland and seems to appeal to people who have never actually been to Loch Lomond, but find the sentiment of the song inspires them to visit.

(Actually, come to think of it, I get a bit sentimental myself on hearing ‘The Lakes of Pontchartrain’, and that isn’t even Scottish, but Irish. At least, it is when Paul Brady sings it. Still, we’re very in tune with Ireland on this site.)

Anyway, what’s the appeal of the song ‘Loch Lomond’? Here are a few notes ( and the words below) – and then we’ll move on looking at the strategic position of the loch.

Ben Lomond from the water.
Ben Lomond from the water.

The Origins Of The Loch Lomond Song

As for the song, some authorities suggest the tune is a variant of the old Scottish ballad ‘The Bonnie Hoose o’ Airlie’.

Others want to link it to the equally venerable ‘The Lowlands of Holland’ – yes, you got to know your Scottish ballads here!

However, most experts agree that the words are quite a bit younger than the tune. The song was first published in ‘Vocal Melodies of Scotland’ (1841). No individual composer is credited.

From the gentler, southern end of Loch Lomond
From the gentler, southern end of Loch Lomond

The usual story is that the lyrics were written by a Jacobite prisoner, while awaiting his fate in Carlisle prison, in England. (It always seems to be in Carlisle – but then the sentimental Victorians were always very inventive.)

Maybe the prisoner was captured after the Battle of Culloden and shipped across the Border; maybe he was taken while the Jacobite army retreated northwards in the previous winter. Or maybe the whole thing is fictional.

But, if it was written around the Battle of Culloden in 1746, then the words with variations must have been around for almost a century before being published.

Ben Lomond beyond Loch Lomond. People often ask how deep is Loch Lomond.
Ben Lomond beyond Loch Lomond.

(Pictured here) Loch Lomond spreads out of the Highlands and on to the Lowland edge.

Here’s the sun that ‘shines bright on Loch Lomond‘ and where the lovers parted on ‘the steep, steep side o’ Ben Lomond‘ –  and that’s Ben Lomond as seen from across the loch, from its south-western end near Balloch.

Again, like Auld Lang Syne, a lot of Scots (at least) can sing their way through the first verse or so, and then things start to get sticky.

By verse two (see below), things are beginning to fall apart, while by verse three we are mired in Scottish sentimentality. Truth to tell, it isn’t great poetry.

The high road and low road allusions are usually explained as the ‘high road’ as in the highway, a physical route, leading home to Scotland.

The ‘low road’ means death, where the spirit of the soldier returns immediately to his homeland.

Lyrics Of ‘The Banks of Loch Lomond’

By yon bonnie banks and by yon bonnie braes,
Where the sun shines bright on Loch Lomond.
Where me and my true love were ever wont to gae
On the bonnie, bonnie banks O’ Loch Lomond.

O ye’ll tak’ the high road and I’ll tak’ the low road,
An’ I’ll be in Scotland afore ye;
For me and my true love will never meet again
On the bonnie, bonnie banks O’ Loch Lomond.

‘Twas there that we parted in yon shady glen,
On the steep, steep side o’ Ben Lomond’,
Where in purple hue the Hieland hills we view,
An’ the moon comin’ out in the gloamin’

The wee birdies sing and the wild flow’rs spring,
And in sunshine the waters are sleepin’;
But the broken heart it kens nae second spring,
Tho’ the waefu’ may cease frae their greetin’.

So, the subject matter of the song is decidedly gloomy – though that doesn’t stop it being played at weddings and rock concert and other upbeat occasions. 

Position of Loch Lomond
Looking north across the River Clyde and an end-on view of Loch Lomond, just spilling into the Lowlands. The Highland hills are in cloud but it’s clear how easy the loch is to reach from the city of Glasgow, just out of shot to the east.

Loch Lomond lies partly in the Lowlands and partly in the Highlands of Scotland.

And, back in the days when Scottish tourism first began, before the end of the 18th century, both Loch Lomond and the Trossachs were areas that were comparatively easy to reach from Scotland’s main cities, especially Glasgow and Edinburgh.

You can see this in the picture above, taken on the approach to Glasgow Airport – we were flying back from a visit to Ireland.

Basically, first the Romantics, even before the very end of the 18th century, then everyone else subsequently, escaped the city and soon found themselves across the Highland Boundary Fault.

There it all got a lot nicer, quite suddenly.

Not just on Loch Lomond and in The Trossachs, but also on the Clyde sea-lochs, minutes away to the west.

The sudden transition from Lowland Scotland – for example, on the journey north from Dumbarton on the Clyde – to the vista of Highland Scotland, revealed from the south end of Loch Lomond, first excited travellers more than 200 years ago.

At that time, the taste of these early visitors was being influenced by the Romantic Movement in the arts and literature.

This involved a new and positive way of perceiving wild and untamed places – as a rebellion against the ‘tamed’ landscapes and the order and symmetry of the Neo-Classical Age that went before.

Ben Lomond from Luss
Spring on the loch. Ben Lomond from Luss – it’s right at the end of April – but the trees still look a bit bare!

The Romantics Discover Loch Lomond

In Loch Lomond and the Trossachs – touched on in the page about tourism in Scotland – the Romantics found scenery exactly to their new tastes – and they found this wild and beautiful place without travelling too far from ‘city comforts’!

Loch Lomond in a historical context was just far enough away from centres of population a couple of centuries back to give a taste of excitement and daring for adventurous travellers.

Famous visitors back then included William and Dorothy Wordsworth who first came this way in 1803. They certainly gave the impression that they were undertaking what amounted to a fearful and unconventional expedition.

Now the loch is within minutes of Glasgow Airport, or an easy journey by road or rail – seemingly closer than when it was first discovered and enjoyed by those early Romantics.

Today, in fact, more than half the Scottish population live within an hour’s drive.

In addition, for more than two centuries, Loch Lomond (and the Trossachs to the east) have been balancing the needs of visitors with the need to retain the essential spirit of wild landscape. It’s a place that, in short, is loved to bits.

That is why since 2002 the area that visitors still enjoy is now in the Loch Lomond and Trossachs National Park. If you want a great experience of the area then we recommend you take a Loch Lomond cruise

Why is Loch Lomond so Deep?

Yes, this brings us back to what this page was originally about. I’ll try to explain here and hope that any geologists reading this will just indulge me a little…

It was all to do with a landscaping company, called Ice Age Glaciers Ltd. They got the contract to make a very large, very attractive loch within easy reach of the populated central belt of Scotland.

(Who issued the contract? Look, do you mind if I just skip that bit?)

Anyway, the Ice Age Glacier Company (no job too large, all materials disposed of) were given lots of time to get the job done.

Actually, it all ran a bit late and they were still working on the Loch Lomond landscaping project about 10,000 years ago (though they’d been at it, off and on, for millions of years before that). They came up with some pretty good landscape designs.

As you can guess from the name, their main digging tool was ice. Tons and tons of it. Their main depot was up on Rannoch Moor where there was a huge ice sheet.

But they moved the stuff south, towards the Highland Boundary Fault, deepening a trench in Glen Falloch.

They’d worked in the area before of course, but mostly doing east-west work. You can see that today after you come down the steep hill to Inversnaid by the side of Loch Lomond. You’ve exited from a hanging valley (in which Loch Arklet sits).

Ooh, a bonus – hanging valleys

Look across the loch and, just opposite, at Inveruglas, there’s another one, only not so steep. The picture here gives you a flavour.

Loch Lomond from Inversnaid
The valley running up behind Inveruglas on the opposite bank of Loch Lomond matches the one from where this pic was taken. But Loch Lomond lies between.

It’s a matching pair of hanging valleys on either side of the loch. The picture here was taken from the foot of one – at Inversnaid – looking west across the loch to the other.

It isn’t as steep as the Inversnaid side though. OK, two matching valleys: opposite sides of the loch. From this you may think that there is some connection.

Well, there used to be. Before Loch Lomond was gouged out, a great river once flowed east from the area west of Inveruglas, around Loch Sloy, across the glen in which Loch Arklet sits, then down by Loch Katrine and on south-east into the Lowlands.

But this changed when Ice Age Glaciers Ltd got the new contract.

So they cut a trench south, right across the east-west old river, and much deeper. After it was filled, we called it Loch Lomond. The old landscapes were changed completely.

Waterfall at Inversnaid
The waterfall from the hanging valley falls into Loch Lomond at Inversnaid

Caution – glaciers at work

But Ice Age Glaciers hadn’t finished yet. They did the same trick further south on the loch.

On the west side, both Glen Douglas and Glen Luss were part of another river system flowing eastwards towards today’s River Endrick and on towards Strathblane and, eventually, the River Forth.

But the cutting of the Loch Lomond trench changed things. Now the little Luss Water enters the loch by the over-run-by-visitors Luss village.

Even glaciers have to start somewhere. Like it’s said above, the one that created our loch was just one of many that trundled out from a great ice sheet in the vicinity of today’s Rannoch Moor.

(The ice went in several directions, by the way – that’s why, in the southern part of the Highlands, the long lochs – including the sea-lochs – seem to radiate like the spokes of a wheel. Loch Lomond is just one of the spokes.)

Anyway, the contract stipulated that the Loch Lomond surroundings had to be scenic. Ice Age Glaciers set out to create a loch with bonnie banks worthy of a well-known song.

First of all, there was a backdrop to make, so that visitors could have a spectacular vista in their photographs.

So the Arrochar Alps on the west side of Loch Lomond were scoured and sharpened.

This was a tough job, as the rocks here are hard. (Geologists call them diorites.)

Loch Lomond – two lochs in one

In fact, hard rocks made the job pretty tough and hence the Loch Lomond trench pretty narrow.

So, grinding slowly southwards, it must have been a relief when the squad got over the Highland Boundary Fault at Balmaha where the ice could spread out and shift a lot of much softer rock.

That’s why Loch Lomond is so much wider at its south end. It’s not in the Highlands. Here, around Balloch or Gartocharn, it’s a Lowland loch.

Where will we put all this rock? All around Balloch?

In any landscaping project you’ve got to dispose of stuff. Ice Age Glaciers had a great idea – they decided to dump all the rocks and gravels, collected in the north, at the south end of Loch Lomond.

This was right at the end of the project, about 10,000 years ago. Otherwise Loch Lomond would have been a sea-loch, like Loch Long is today.  

(At one time in its glacier story, Loch Lomond actually was a sea-loch – though sea-anglers were scarce in those days.)

So Loch Lomond was effectively dammed by the glacial spoil – and it is only 27 ft (8m) above sea level.  All this means is that, on a geological time-scale, the ‘Bonnie, bonnie banks’ were created just the other day – as the last job undertaken by Scotland’s Ice Age Glaciers Ltd.

That company isn’t around anymore. It just got too hot for them.

Hmm. Since you’ve arrived here, you’d find a comparison between Loch Lomond and Loch Ness useful. Take a look.