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Loch Katrine and aqueducts
Loch Katrine, Stirling, Scotland, UK
associated engineer
John Frederick La Trobe Bateman
James M. Gale
date  1855 - 14th October 1859, 1885 - 1901, 1909 - 1914, 1919 - 1929
era  Victorian  |  category  Aqueduct  |  reference  NN489067
ICE reference number  HEW 1808/03
Water from Loch Katrine in the Loch Lomond & Trossachs National Park has been delivered via aqueducts to Glasgow since 1859. The aqueducts are a crucial element of the city’s water supply network. Though the scheme has been augmented and improved over the years, the original aqueducts remain in continual use.
Glasgow’s water was drawn from wells and streams until 1807, when Thomas Telford (1757-1834) and James Watt (1736-1819) built a new supply works at Dalmarnock (NS618632) on the north bank of a loop in the River Clyde. Another water works was completed in 1819 at Cranstonhill to the west of Dalmarnock. However, the river became progressively more unsuitable as a source of potable water and there were frequent complaints about its quality. Cholera was rife in densely populated areas of the city.
New reservoirs were built to the south west of the city and the Gorbals Gravitation Water Co. used them to supply high quality water to south-central Glasgow and Renfrew from 1846 onwards. This was still not sufficient, and a cholera epidemic in 1848-9 claimed some 4,000 lives. It wasn't until the waters of Loch Katrine were accessed that a copious supply of clean water was obtained.
The idea of bringing in water by gravity from Loch Katrine, 55km north of Glasgow, was suggested as early as 1846 by Lewis Dunbar Brodie Gordon (1815-76) — the UK’s first professor of engineering. The project was developed by William John Macquorn Rankine (1820-72) and John Thomson in 1852.
Later in 1852, leading water engineer John Frederick la Trobe Bateman (1810-89) — famous for designing Manchester’s water supply system — was brought in to review the various possibilities for improving Glasgow’s water supply. In 1853, he reported that raising the level of Loch Katrine just 1.2m could supply 227.3 million litres of water per day to the city.
He advised that “no other source” than Loch Katrine “will meet all the requirements of the case”. This view was supported by fellow engineers Robert Stephenson (1803-59) and Isambard Kingdom Brunel (1806-59) in 1854. The scheme was approved under Glasgow Corporation Water Works Act passed on 12th July 1855, and Bateman designed and constructed the works as built from 1855. James M. Gale (1830-1903), Chief Engineer to Glasgow Corporation Waterworks, acted as resident engineer and was responsible for the rearrangement and redistribution of the pipework within the city. He was to play a continuing role in the supply of water to Glasgow.
One of the major objections to the scheme was that flow in the River Teith exiting Loch Vennachar west of Loch Katrine would be reduced, in turn reducing water levels in the River Forth. To counter this, compensation water was provided by building a masonry dam (NN597064) at the western end of Loch Vennachar in about 1857. It has 11 sluices, a weir and a fish ladder for migrating salmon.
The natural summer level of Loch Katrine was raised by some 1.2m with a small dam and, by providing a draw-off point 910mm below the natural outlet, the top 2m of water was fed through an aqueduct network by gravity to Glasgow.
The aqueduct network cost £468,000 and is in two parts — the first 41.5km long, between Loch Katrine and Mugdock Reservoir (NS556759) in East Dunbartonshire. Some 14.5km of arched aqueduct was built in open cut and 21km involved tunnelling through hard rock, mostly under spurs of Ben Lomond, while the final 6km consists bridges over river valleys. The second part is a 13km aqueduct of twin cast iron pipes from Mugdock Reservoir to Glasgow.
The 2.4m diameter subterranean tunnels are unlined and have been constructed to a flat gradient of 158mm per kilometre (1 in 6,336). All the rock boring had to be done by hand as this was before pneumatic tools were available.
The second longest of the 70 tunnels, immediately after leaving Loch Katrine, is 2,126m long and lies 183m below the summit of the hill. It was worked from 12 shafts, five of which are almost 152m deep. The rock is gneiss and mica slate. About 60 drills were constantly in use at each face and on average a fresh drill was required for every 25mm gained in depth.
There are 25 substantial iron and masonry aqueduct bridges, up to 24m in height and 27.4m in span, crossing the deep valleys of the Duchray, Endrick and Blane. The water is carried in cast iron siphon pipes with a fall of 947mm per kilometre (1 in 1,056). A typical example is the bridge in the Duchray Valley.
This 194m long three-span aqueduct bridge consists of a rectangular cast iron tube about 2.5m high and 2m wide, carried on masonry piers 15.85m above the ground at the lowest point. The tube contains two 1.2m diameter cast iron pipes, one above the other. The first was installed in the 1850s and the second was added in the 1860s. A third pipe of just over 1m diameter was installed in 1881, carried on an adjacent mild steel trussed girder bridge supported by red sandstone piers with whinstone rubble abutments at each end.
Of the other bridges, the five principal ones consist of cast and wrought iron troughs on masonry piers with masonry embankments at each end. The longest is the 304m long aqueduct bridge at Corrie (NS485957), with a 134.4m long one over Castle Burn (NS470988) and three at Couligartan (NN450002) of 113.4m, 140.8m and 194m in length. The masonry supports for these bridges were built originally with dry stone joints but mortar jointing was added in the early 1860s.
Though the aqueduct was designed to carry 227.3 million litres of water per day, monitoring showed it was capable of carrying only 191 million litres per day owing to friction losses over the rough surfaces of the unlined tunnels.
Queen Victoria inaugurated the Loch Katrine scheme on 14th October 1859 by opening a sluice near the centre of the south bank at Royal Cottage to allow water from the loch to flow into the aqueduct. It was one of the largest water works ever constructed. It delivered plentiful high quality water, from a catchment area of 9,230ha, for the relatively low total cost of £918,000. About 3,000 people were employed on the whole project, excluding iron founders and mechanics.
Water began flowing into Glasgow on the 28th of December 1859, and by March 1860 the supply extended throughout the city. Gale wrote of the project — “It is a work which will bear comparison with the most extensive aqueducts in the world, not excluding those of ancient Rome; and it is one of which any city may well be proud”.
By 1883, demand in Glasgow was outstripping supply. Under Parliamentary Acts of 1883 and 1885, authority was obtained to raise the level of Loch Katrine a further 1.5m and a new masonry dam was built just below the original, with nine sluices replacing the four earlier ones for regulating compensation water. Another aqueduct was constructed too, increasing the scheme’s capacity to 318 million litres of water per day. Raising the levels of Lochs Vennachar and Drunkie, with a combined drainage area of 9,310ha, provided additional compensation water of 184 million litres per day.
The new aqueduct was designed by and executed under Gale’s direction. He decided not to follow closely the line of the 1855 aqueduct as the large bridges, particularly in the Duchray Valley, were its least satisfactory feature. He adopted a more direct route further into the hills. Although a greater length of tunnelling was involved, it was facilitated by the availability of pneumatic drills and more powerful explosives. A length saving of about 3.6km was achieved.
Friction losses were reduced, because about 53% of the aqueduct’s length was lined with concrete. These tunnels are all 2.7m high with a round-topped coffin shaped cross section, the lined sections are 3m wide and the unlined portions are 3.7m wide.
There are also fewer bridges on this later aqueduct. There were five masonry bridges, including the single span granite-faced concrete arch at Tom an Eas (NN438006). Another service reservoir was completed in 1896 at Craigmaddie (NS563754), on the east side of Mugdock Reservoir. The second phase of the Loch Katrine scheme opened on 21st June 1901.
In 1902, a Parliamentary Bill was passed to allow a 320m long dam (NN356093) to be built at the west end of Loch Arklet, to provide extra water for Loch Katrine via a tunnel link. Construction began in 1909 and it was operational in 1914.
In 1903 and 1915, further Parliamentary Bills authorised building a dam (NN529079) across the River Turk at the south end of Glen Finglas to provide another reservoir for the scheme. However, World War I (1914-18) and subsequent rising construction costs meant deferral in favour of raising Loch Katrine’s water level again. The connecting tunnel and reservoir at Glen Finglas were not completed until 1958 and 1965 respectively.
The third raising of Loch Katrine took place in 1919-29 when another 1.5m was added to the Achray Dam at its eastern end. This allowed the city to use a 5.2m depth of water, which provided nine months storage supply. The dam was lengthened also to over 73m. A protective cofferdam was added during World War II (1939-45). The dam now has 13 sluices, of which six have gates.
As more-stringent European Union directives on drinking water quality came into effect in December 2005, even the clean water from Loch Katrine needed extra treatment. Raw water from the loch is treated at the existing works at Balmore (NS603741) and a new £120m underground treatment plant at Milngavie (NS561760), completed in 2008, before flowing into the Glasgow supply network.
West of Scotland Water now operates the Loch Katrine scheme. Many of its structures are listed buildings — Loch Arklet Dam, Loch Vennachar Dam and the aqueduct intake at Royal Cottage are all designated Category A. Of the aqueduct bridges built 1855-1901, there are six of Category A, five of Category B and two of Category C(S). There are also a further eight Category B and two Category C(S) structures.
Resident engineer: James M. Gale
Ironwork (Castle Burn and Corrie aqueduct bridges): Wylie Smith Davie
Ironwork (Couligartan aqueduct bridges): Alston & Gourlay
Contractor (Loch Chon aqueduct bridge No.3): Robert Simpson, John Parkinson and Joseph Mann, Halifax
Research: ECPK
"Obituary: John Frederick La Trobe Bateman 1810-1889" by Alexander Fairlie Bruce, in Minutes of ICE Proceedings, Vol.97, pp.392-398, London, 1889
"Observations on the Flow of Water in the New Aqueduct from Loch Katrine: Glasgow Corporation Waterworks. (Including Appendix)" in Minutes of ICE Proceedings, Part 1, Vol.123, pp.410-414, London, 1896
reference sources   CEH SLB

Loch Katrine and aqueducts