The Bathymetrical Survey of the Scottish Fresh-Water Lochs was carried out during the years 1897–1909 under the direction of Sir John Murray and, in the main, Lawrence Pullar. The six volume compilation (Murray and Pullar, 1910), comprising a grand total of 562 loch (lake) bathymetric maps, together with extensive supporting biological, chemical, geological and physical information, represents an outstanding record of one of the most remarkable feats of field-based scientific endeavor of the late nineteenth and early twentieth centuries. No other country can boast such an important limnological archive; it remains today without equal and has renewed significance thanks to the requirements of the European Union (EU) Water Framework Directive (2000).
Canadian-born Murray (1841–1914), of Scottish parents, was educated at Stirling High School and the University of Edinburgh. He rose to fame as a pioneering oceanographer and marine biologist who played a pivotal role as assistant leader of the Challenger Expedition, which explored the deep oceans of the world from 1872 to 1876. He was subsequently responsible for editing and publishing over 50 volumes of expedition reports and was duly knighted in 1898. He returned to Scotland in the 1880s with the intention of undertaking nearshore oceanographic investigations around the coast. With the financial support of his good friend Lawrence Pullar, of Bridge of Allan, Stirlingshire, Murray built the 30 ton steam yacht Medusa, which from 1884 until 1891 was employed in the exploration of the nearshore waters around Scotland, including the deep glacially scoured sea lochs of the west coast (Duck, 1990). At this time, it became evident to Murray that virtually nothing was known of the depths of the innumerable fresh-water lochs of the country that formed such a significant scenic legacy of Pleistocene glaciation, especially in the Highlands. Naval officers had, in the interests of navigation, surveyed Lochs Lomond and Awe around 1860, and Murray himself had made a series of depth soundings along the long axis of the lochs connected to create the Caledonian Canal. However, this, along with some soundings in Lochs Katrine, Lomond, and Tay (Buchan, 1871), was the total knowledge of the bathymetry of the Scottish fresh-water lochs at that period.
Murray saw this as a huge gap in knowledge and proposed a systematic survey of the depths of Scotland’s fresh-water lochs which he believed would, “in all likelihood result in many new additions to natural knowledge, and would be especially important for comparisons with results in other departments of scientific endeavour” (Murray, 1910). Many parties were interested in the depths of loch basins, such as geologists, in connection with their mode of formation (e.g., Wilson, 1888), fishermen and water supply engineers (Loch Katrine, for example, had become the principal water supply for the City of Glasgow in 1859). On Murray’s initiation, the proposal was brought before the Councils of the Royal Societies of Edinburgh and London, both of which were in strong support and, in consequence, urged the British Government of the day in 1883 and 1884 to finance the surveys “in the interest of scientific progress” (Murray, 1910). Treasury support was not, however, forthcoming largely because of a lack of responsibility for inland bodies of standing water: the Scottish fresh-water lochs fell neither under the remit of the Admiralty, whose work was confined to the interests of navigation, nor the Ordnance Survey, whose mapping operations were confined to dry land.
The Murray and Frederick Pullar Surveys
It is credit to Murray’s determination and belief in the scientific merit of such a systematic survey that the idea was not allowed to die in 1884. However, it appears to have lain dormant for several years until it was reinvigorated with the keen enthusiasm of Frederick Pattison Pullar, son of Murray’s good friend and benefactor Lawrence. Together Murray and Pullar, the younger, undertook to embark on bathymetric surveys at their own expense, thus commencing an operation that was initially regarded as a “holiday task” in 1897. By that year, however, knowledge of the depths of Scotland’s fresh-water lochs had increased somewhat as, in the interim, four bathymetric surveys had been carried out by and officer of the Geological Survey of Scotland, J. S. Grant Wilson. In connection with his studies of the glaciation of the County of Perthshire, Wilson (1888) undertook soundings of the four so-called chief Perthshire lochs, namely, in order of decreasing surface area, Lochs Tay, Rannoch, Earn, and Tummel, for which he recorded maximum depths of 510, 420, 268, and 124 feet, respectively (c. 155, 128, 82, and 38 m, respectively). The results of this pioneering work, incorporating a small, colored, contoured bathymetric map of each water body, were published in the Scottish Geographical Magazine (Wilson, 1888). Little is known of Wilson’s survey methods or the equipment he used, other than he took a series of depth soundings 50–80 yards apart (c. 46–73 m) along parallel traverses, from one side of a loch to the other (these are all relatively long, narrow, glacially scoured, rock basin lochs), spaced at intervals of about a quarter of a mile (c. 0.4 km). It is presumed that he must have used some form of weighted line; a steam-powered launch was employed to survey the largest body, Loch Tay, while for the other lochs, a rowing boat proved adequate.
Murray and Frederick Pullar commenced their formidable undertaking close to their Stirlingshire homes choosing to survey lochs in the drainage basin of the River Forth, in particular those of the Trossachs and Callander area of the southern Grampian Highlands. Three years later, by 1900, they had completed surveys of eight water bodies, Lochs Katrine, Arklet, Achray, Vennacher, Drunkie, Lubnaig, Voil and Doine for which colored, contoured charts were initially published in the Scottish Geographical Magazine (Murray and Pullar, 1900). One year later, in 1901, bathymetric charts of the remaining four major lochs of the Forth basin, Chon, Ard, Leven, and the Lake of Mentieth (Scotland’s sole “lake”), together with two lochs of the neighboring Tay drainage basin, Ericht and Garry, were published in the same journal (Murray and Pullar, 1901a, b).
Prior to beginning their surveys proper, Murray and Frederick Pullar made many trial attempts to measure water depths using various devices. As none had proved entirely satisfactory, Pullar, who was of an inventive nature (Chumley, 1901), designed and built what was subsequently to become known as the “F.P. Pullar Sounding Machine.” This was mounted on the gunwale of a boat and comprised a drum around which was wound galvanized steel wire, which passed around a measuring pulley to a tubular weight. The system was such that for every foot (c. 0.3 m) of wire that ran out, the measuring pulley made one complete turn. The motion of the pulley was transmitted mechanically to a series of dials that indicted the length (in feet) of wire paid out in the water column. This ingenious piece of equipment was so successful and reliable that it was employed in all surveys except those in small, poorly accessible hill lochs in which graduated hand lines were used (Murray, 1910).
By the beginning of 1901, Murray and Frederick Pullar had completed a total of 14 loch surveys, and their target of countrywide coverage must have seemed long distant or even unattainable. In February of that year, tragedy struck; on the 15th of the month, Pullar lost his life at the age of 25. Along with many others, he was skating on Airthrey Loch, close to his Bridge of Allan home, when the ice cover gave way. Pullar helped three people to the shore but heroically drowned while trying to rescue a young woman who was suffering from exhaustion in the water. Onlookers claimed that, “he might easily have saved himself had he relinquished his burden: this he refused to do” (Murray, 1910). Murray, who had been out of the country for some months on a round-the-world voyage, arrived back in Britain to learn of his young friend’s death the previous day (Chumley, 1901).
This tragedy brought the loch surveys to an immediate halt. Indeed, Murray (1910) wrote that it was his intention to abandon the project altogether. However, Murray’s old friend Lawrence Pullar, Frederick’s father, was convinced as to the scientific merit of the work and insisted that the surveys should continue as a memorial to his son. To expedite this, he generously donated £10,000 into a trust fund to provide the means to continue the project and took over his son’s role as co-director. Such a sum would be equivalent to c. £850,000 today (2007).
The Murray and Lawrence Pullar Surveys
Now placed on a secure financial foundation, the loch surveys recommenced in the spring of 1902, a year after Frederick Pullar’s death. The generous funding enabled the employment of a large team of scientific and technical personnel; 48 individuals took part, for longer or shorter periods, including biologists, geologists, physicists, zoologists, surveyors, boatmen and cartographers, as well as numerous boatmen and assistants employed temporarily in different parts of the country. By 1909, when the field operations were drawn to a close, an enormous total of 562 water bodies had been surveyed. “All lochs were surveyed,” wrote Murray (1910), “on which boats could be found at the time the work was being carried out.” This impressive total comprised not only the major, well-known, “iconic” Scottish lochs (such as Loch Ness and Loch Lomond) but also numerous smaller and less familiar water bodies throughout the country, including several man-made water supply reservoirs (such as those of the Lomond Hills group, Fife), and many complex, shallow lochs in Shetland, Orkney and the Western Isles. In all, the surveyors recorded over 60,000 point “soundings” of water depth.
When measuring water depth, it is important that the position of the boat is established with accuracy. The Murray and Pullar surveys preceded the use of precision position fixing by techniques taken for granted today (e.g., GPS); they were conducted along traverses between known end points, typically prominent shoreline features such as deltas at the mouths of influent streams or buildings that provided a clear line of sight. Uniform spacing of soundings was accomplished by recording the water depth as quickly as possible so as to avoid boat drift after a fixed number of strokes (typically 10, 15, 20, or 50 according to the length of traverse) by the oarsman. In order to keep the boat on course when running lines of soundings, an aligning mirror was often used in the survey boat. By this means, an onshore feature behind the surveyor could be kept in line with a feature in front on the opposite bank.
During the period of the loch surveys, measurements of water temperature, movements (surface and internal seiches) and chemistry, loch biology and the character of the bottom sediments were also carried out. The bathymetric maps themselves are masterpieces of cartography, prepared and color lithographed by J. G. Bartholomew & Son of Edinburgh at a scale of 3 in. to 1 mile (1: 21,120). The depth soundings were contoured at regular intervals, each division being colored in a shade of blue, becoming progressively darker with increasing depth. Around half of the 233 plates that comprise the 562 individual maps also show the topography shaded with darkening shades of brown indicating progressively higher relief. The later maps in the series (those of Murray and Pullar, 1910, Vols. 5 and 6) show only the blue colorations of water depth. The maps, together with a descriptive account of each loch, chapters on the associated scientific observations and tables of statistics relating to the suite of water bodies (length, surface area, maximum depth, mean depth, volume; the interrelationships between which have been evaluated by Gorham, 1958), were collated into six volumes and published by the Challenger Office, Edinburgh (Murray and Pullar, 1910). At the time the six volume set, representing around 12 years of fieldwork, retailed at five guineas (£5.5 s.0d = £5.25p). Today, the maps have been made available free of charge on the Internet by the National Library of Scotland (http://www.nls/uk/maps/early/bathymetric/).
The deepest sounding measured in all of the c. 60,000 of the 562 surveys was of 1, 017 ft (309.98 m) in Loch Morar. The second deepest was found to be Loch Ness (maximum 754 ft, 229.82 m), followed by Loch Lomond (632 ft, 192.63 m), Loch Lochy (531 ft, 161.85 m), Loch Ericht (512 ft, 156.06 m), Loch Tay (508 ft, 154.84 m), Loch Katrine (495 ft, 150.88 m) and Loch Rannoch (440 ft, 134.11 m). In his introduction to the six volumes, Murray (1910) reflected that, “It was rather amusing at times to observe the result of the soundings on the inhabitants of districts in which the lochs are situated. As a rule, lochs, or some parts of a loch, are regarded as very deep or without bottom. When a loch with this reputation was found to be relatively shallow, the result would be questioned, and a feeling of affront or injury prevailed among the inhabitants of the district.”
Significance of the “Murray and Pullar” Surveys Today
In the intervening century since the “Murray and Pullar” surveys were completed, the character of Scotland’s lochs has changed considerably, not least in the Highlands. The advent of hydroelectric power generation following World War II has resulted in the construction of large numbers of mass concrete, buttress and arch dams. In some valleys, these have created new lochs (e.g., Loch Faskally, Loch Errochty), whereas at other sites, dams have raised the water levels, and thereby the surface areas, of existing lochs (e.g., Loch Tummel, Loch Garry). Natural sediment influx and, in places, increased rates associated with land use changes have continued to contribute to delta growth at the mouths of influent rivers and streams and to offshore loch floor deposition. The Murray and Pullar surveys thus represent important baselines from which to evaluate such changes in hydromorphology a century or so later.
Where re-surveys of water bodies have been undertaken with modern methods of sounding and position fixing (e.g., Duck and McManus, 1985; Duck, 1986; Lowe et al., 1991a, b; Young and Shine, 1993) and the bathymetric data can be directly compared with those of Murray and Pullar, the differences serve to emphasize the accuracy of the latter. While modern methods may reveal deeper hollows that the original surveyors missed using point soundings, the overall morphology of the basins was accurately captured using what today are regarded as relatively primitive surveying techniques.
In recent years, the Murray and Pullar surveys have assumed an even greater significance due to The EU Water Framework Directive (WFD), which was introduced in 2000 to establish a new legal framework for the protection, improvement and sustainable use of all water bodies, including lakes, across the European Union. The Directive stipulates that surface water bodies, such as lakes, should achieve good ecological and chemical status by 2015. Implementation of the WFD presents a series of challenges to EU member states, one of which concerns the lack of adequate baseline data, such as lake bathymetry. For example, Great Britain (England, Wales and Scotland) has over 40,000 lakes >1 ha in surface area (and thus covered by the WFD), but bathymetric data are available for less than 2% (Rowan et al., 2006). Morphometric data, for example lake volume, derived from bathymetric surveys, are necessary for the calculation of important parameters such as basin residence time. The requirement for good quality bathymetric data is essential for lake management and for the effective compliance of the WFD. When such data are not available, it is necessary to make estimates based on empirically derived relationships from map-derived parameters and predictive models that derive from actual bathymetric data (Rowan et al., 2006). The 562 Murray and Pullar surveys from Scotland, even though they actually cover only a small fraction of the lochs in the country, represent over 90% of the currently available bathymetric data for lakes in Great Britain. They are thus of prime importance as input data to such predictive models, that vary according to lake typology, and collectively place Scotland at an advantage for WFD implementation in terms of the quality and quantity of its baseline lake bathymetric data.