Bathymetrical Survey of the Fresh-Water Lochs of Scotland, 1897-1909
The Bathymetrical Survey of the Fresh Water Lochs of Scotland was the first comprehensive examination of the depths and nature of Scottish lochs. Over 10 years some 60,000 soundings were taken of all the major Scottish lochs, some 562 in total, resulting in the first detailed charts of all their depths.
The entire project was conceived and organised through the perseverence of Sir John Murray, the oceanographer, and funded by his lifelong friend Laurence Pullar, whose son Fred tragically drowned in the early years of the Survey.
The Bathymetrical Survey was not only widely recognised at the time, placing Scotland at the forefront of organised lake studies or limnology, but the resulting published reports and maps are still of major value today.
Information about the Survey is organised in the following sections below:
- A few bathymetrical facts from the Survey...
- Soundings and their position
- Preparation and publication of the maps
- The deepest loch was found to be Loch Morar at 1,017 feet deep. This could fit the Eiffel Tower within it with 33 feet to spare! Loch Ness was in second place (754 feet deep), Loch Lomond third at 623 feet. (It is also of interest that these depths are often substantially greater than the sea around Scotland; for example, the sea does not reach the depth of Loch Morar until the dip of the continental shelf beyond St Kilda).
- Loch Ness has the greatest mean depth at 433 feet, followed by Loch Morar (284 feet) and Loch Lochy (228.95 feet).
- Loch Ness has by far the greatest volume of water within it, measured at 263,162 million cubic feet. It is followed by Loch Lomond (92,805), Loch Morar (81,482) Loch Tay (56,550) and Loch Awe (43,451 million cubic feet).
- The total volume of fresh water in all the lochs combined was calculated as 1,015,814 million cubic feet, or 6.9 cubic miles.
- The longest lochs in Scotland then and now are Loch Awe (25.47 miles), then Loch Ness (24.24 miles) and thirdly Loch Lomond (24.23).
- Loch Lomond has the greatest surface area, at 27.45 miles, followed by Loch Ness (21.78 miles), Loch Awe (14.85) and Loch Maree (11.03). The total surface area of all 562 lochs surveyed was calculated at 340.22 square miles.
The inland or fresh water lochs of Scotland have long captured the interest of former generations, although before the 18th century all reports of their depths and mysteries were based more on myth than on practical observation. For example, on Timothy Pont's map of Strathnaver is his reference to 'a monstrous hole, 180 fatham deepe' in Loch Ereboll, whilst more usefully both the Blaeu Atlas texts (1654) and the later Statistical Accounts (1791 and 1845) have many references to abundant resources of fish in lochs. One of the earliest maps of Scottish lochs with depths is by the military surveyor Joseph Avery of the Great Glen Lochs (ca. 1727) in our Board of Ordnance Collection.
It was not until the 1860s that actual measurements were systematically recorded, initially by the Hydrographic Department of the Admiralty on Lochs Lomond and Awe, with some depths also recorded along the Great Glen. Further work was done on Lochs Lomond, Tay, and Katrine (Buchan, 1871), the latter partly due to the plans to supply water from there to Glasgow, and Buchanan (1887) recorded a depth of 320 metres in Loch Morar whilst researching temperatures and freezing. In 1888, Wilson published an account of Lochs Tay, Earn, Rannoch and Tummel, accompanied by simple contoured maps with soundings, to illustrate his study of the glaciation of the district.
This essentially represented the state of knowledge of the depths of Scottish fresh water lochs at the time Sir John Murray began his systematic survey in 1897, with the assistance of his friend Fred Pullar. Murray was an experienced oceanographer, who had become very interested in the different physical and biological conditions presented by sea and fresh water lochs. He recognised that a systematic survey of fresh water lochs would result in many new additions to scientific knowledge, and would assist the growing number of geologists, fishermen, and engineers who were also interested in these matters.
He brought the subject before the Royal Societies of Edinburgh and London, who in 1883 and 1884 made strong representations to the government on the value of such a survey. However, despite acknowledging the value of such a survey, the response from the Treasury indicated that the work was not in the interests of navigation and so fell outwith the functions of the Admiralty, whilst the Ordnance Survey would confine its attentions to dry land. As Murray concluded, 'we were led to take up this self-imposed task because ... there was no hope of the work being undertaken by any Government Department.' (Murray & Pullar, 1910 vol. 1, p. 4).
So from 1897 work began slowly on the lochs of the Forth, with some lochs surveyed two or three times with different sounding machines and methods before satisfactory results were obtained. A first paper was published in 1900 on the lochs of the Trossachs and Callander district, before tragedy struck. Fred Pullar drowned in February 1901 at he age of 25 whilst gallantly rescuing people who had fallen through ice on Airthrey Loch. It was initially Sir John Murray's intention to abandon the Survey altogether, but at the request of Fred's father Laurence, who donated the sum of £10,000 to a trust to support the project, the work continued.
In fact the donation allowed work to continue on a sounder footing with appropriate staff, and many scientific advisors. During 1902, work progressed rapidly on the lochs of the Tay basin, covering 154 lochs, whilst during 1903, some 250 lochs were surveyed. Therafter, surveying work proceeded more gradually to completion in 1906, with further biological and physical recording continuing until 1909.
The choice of which lochs to include was ultimately determined by common sense. 'The only Scottish lochs left unsounded were those which had no boats on them, or to which boats could not readily be transported' (Murray & Pullar, 1910, vol. 1, p. 9). Obviously the line had to be drawn somewhere, and numerous smaller lochans were excluded. Nevertheless, at the smaller end of the spectrum, we find Loch Setter in Shetland included, barely 400 yards long, 0.02 of a square mile in extent, on average one foot deep, with a maximum depth of two feet.
The accuracy of the soundings have generally been confirmed by later 20th century technology. For example, the Loch Ness bathymetric and seismic survey in 1992 using sonar measurements recorded a depth of 786 feet, only 32 feet more than the Bathymetrical Survey (Young & Shine, 1992). The Survey charts are also obviously an important historical record, especially where 20th century changes in the environment or due to hydro-electic dams have substantially altered the lochs. The Ordnance Survey never undertook detailed survey work on loch depths, and the submarine contours on their 6 inch to the mile and smaller scale maps from the 1900s onwards have been based on the Bathymetrical Survey.
The Bathymetrical Survey also recorded and published much new data on lochs, including studies of the oscillations of water or 'seiches' on lochs, which can affect the water at some considerable depth below the surface without being recognisable at the surface. More than 700 species were enumerated by the Survey, including 450 invertebrates and nearly 200 algae. At least 29 of these species were described as new, and about 50, although not new, were additions to the previously known fauna and flora of the British Isles (Maitland, 1983). (The field note books of the Bathymetrical Survey were deposited in the National Museums of Scotland).
Buchan, A., 'Remarks on the deep-water temperature of Lochs Lomond, Katrine and Tay'. Proceedings of the Royal Society of Edinburgh 7 (1871), 791-795.
Buchanan, J.Y., 'Distribution of temperature in Loch Lomond in the autumn of 1885', Proceedings of the Royal Society of Edinburgh 10 (1886), 403.
Duck, R.W., 'The charting of Scotland's lochs', Forth Naturalist and Historian 13 (1990), 25-30.
Gracie, J., 'The men who plumbed the depths', Scots Magazine (1994), 609-617.
Maitland, P., 'Freshwater science', Proceedings of the Royal Society of Edinburgh, Series B, 84 (1983), 171-210.
Murray, J. & Pullar, L., Bathymetrical survey of the freshwater lochs of Scotland (Edinburgh, 1910).
Wilson, J.S.G., 'A bathymetrical survey of the chief Perthshire lochs', Scottish Geographical Magazine 4 (1888), 251.
Young, I & Shine, A.J., 'Loch Ness bathymetric and seismic survey', The Scottish Naturalist 105 (1993), 23-43.