Ancient Monuments

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Loch Thom-Overton, water cut

A Scheduled Monument in Inverclyde South West, Inverclyde

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Latitude: 55.9353 / 55°56'7"N

Longitude: -4.8024 / 4°48'8"W

OS Eastings: 225048

OS Northings: 674907

OS Grid: NS250749

Mapcode National: GBR 0B.Z13P

Mapcode Global: WH2MH.62DR

Entry Name: Loch Thom-Overton, water cut

Scheduled Date: 26 October 1972

Last Amended: 2 September 2011

Source: Historic Environment Scotland

Source ID: SM3244

Schedule Class: Cultural

Category: Industrial: inland water

Location: Greenock/Inverkip

County: Inverclyde

Electoral Ward: Inverclyde South West

Traditional County: Renfrewshire


The monument comprises an aqueduct, reservoir, sluices, sluice houses and workmen's bothies, commonly known as 'The Greenock Cut'. The monument is part of a larger water system built to provide drinking water for Greenock and water power for industry in the town. Water was collected from the moorland to the south of Greenock and conveyed around the aqueduct to the town's mills. The monument was designed by Robert Thom and built between 1825-7 by Shaw's Water Company. The aqueduct became obsolete in 1971 when a tunnel was opened from Loch Thom to the town. The monument is located in rough pasture at 165m above sea level. The monument was first scheduled in 1972. It is being rescheduled to refine the scheduled area and update the associated documentation.

The aqueduct is around 7.9 km long, originating from the W end of the Loch Thom compensation reservoir at NS 246 720. The aqueduct flows along the 165m contour line to the west and curves in a clockwise direction around the northern slopes of the moorland to the south of Greenock, eventually turning east and terminating at NS 266 748. The channel drops 10.5m along its length. The aqueduct channel has an average width of 3m by 1.5m deep and is rock-cut in places. Where the channel is not rock-cut, the bed is lined with a vermin-proof clay and gravel mixture; the downslope, and sometimes upslope, sides are constructed of dry-stone walling. A continuous embankment, the crest of which supports a footpath, is located on the downslope side. Twenty-three bridges, the majority masonry footbridges, cross the aqueduct, providing access to the farmland on either side. Those at NS 240 720 and NS 266 748 support minor roads.

An original masonry sluice house at NS 239 721, now restored, measures 2.3m E-W by 1.9m transversely. It is built into the embankment and contains elements of the original mechanism. At NS 235 724 is a stone-built bothy measuring 3.6m WNW-ESE by 2.6m transversely. It has a flat concrete roof and a fireplace in the SW wall. A masonry sluice house with a vaulted roof is located at NS 233 726. It measures 2.8m NE-SW by 2.3m transversely. A metal balcony projects from the SW side. A masonry sluice house at NS 231 733 measures 3.4m NE-SW by 3m transversely. The structure has been re-pointed and is unroofed and without wall head or gable. One side of the entrance survives.

A second bothy, oriented NE-SW, is located at NS 238 737. It measures about 4m square and is built into the embankment in a steep bend in the aqueduct. The roof and front gable are missing. The entrance is in the NE wall. A fireplace survives on the back, SW, wall. The walls have been capped. Two sluices are located around 34m and 97m to the N of the bothy controlling water into the Spango Burn. The first is complete and a sluice house has been removed from the site of the second. It is marked by a stone-built channel entry from the burn upslope. The sluice gate is under a stone arch topped by a concrete path under the embankment path. Another sluice mechanism is located at NS 2468 7460. The metal parts of the gate and screw mechanism are intact. The footpath is carried on a concrete slab over the sluice. A third masonry bothy is located at NS 246 746. It is built into the embankment and measures around 3.7m square. The barrel vaulted roof is incomplete and the N wall is missing.

A further three sluices are located at Hole Glen at a point where three burns flow into the cut. The main sluice has a sluice house at NS 2601 7468 measuring 3.7m WNW-ESE by 3.4m transversely. Another sluice gate 80m to the NW controls water into a small artificial channel outwith the scheduled area. The third sluice is located at NS 2603 7468.

At the E end of the aqueduct at Overton, the cut passes under a road bridge and flows into the 'Long Dam', a holding reservoir. The bridge, of rendered blockwork, has a cast iron decorative drinking fountain and two commemorative plaques on its W side. The reservoir, originally 500m long and up to 25m wide, is contained within an embankment of interlocking granite boulders. At the NW end of the reservoir is a sluice house controlling water to an overflow tank. The sluice house is around 3.7m square and the exit channel from the reservoir into the holding tank, around 6m wide, is located 18m to the south-east. The footpath continues around the N side of the reservoir and crosses the exit channel over a galvanised metal footbridge. The final extant sluice is located in the N side of the reservoir at NS 269 748. There is no visible exit channel.

The area to be scheduled is irregular in plan to include all the remains as described above and as shown in red on the accompanying map. The scheduled area of the Long Dam comprises the extent formerly covered by water and the sides of the reservoir, except for the E end where it extends up to but excludes the boundary of the electricity sub-station. The scheduled area specifically includes the entire slope of the embankment along the downslope side of the aqueduct and a further 5m on the upslope side of the channel. Specifically excluded from the scheduled area are all modern laid path and road surfaces, the above-ground elements of all fences, dykes, telegraph poles, and any sluice mechanisms replaced or installed since 1972, to allow for maintenance. At Shielhill Farm, the N edge of the scheduled area extends up to but excludes the southern boundary of the farm.

Source: Historic Environment Scotland

Statement of Scheduling

Cultural Significance

The monument's cultural significance can be expressed as follows:

Intrinsic characteristics

Shaw's Water Joint Stock Company was incorporated on 10th June 1825 and the system was officially opened on 16 April 1827. The monument is a significant part of an early 19th-century civil hydraulic engineering scheme. The system was devised to supply enough water for the burgeoning population of Greenock and to provide power for the rapidly developing industries of the area. Thom designed a novel mechanism that was automated by the action of the overflowing water during flood periods and was known as a 'waster'. This system enabled excess water to be let out of the cut at natural watercourses along its length and would automatically shut off when the flow decreased. Problems with blockages from snow in winter, deterioration of the structure, and fear of contamination led to the construction of a tunnel to channel water directly from Loch Thom to Greenock. The monument became obsolete in 1971.

The aqueduct retains many original features, such as the clay lining and stone walling of the channel and the embankment, as well as sluice houses, gates and workmen's bothies, built to house those maintaining the cut. Parts of the cut are still in water and, with the benefit of active maintenance and restoration, the monument is in a state of good preservation. The retention of original sluice mechanisms is particularly important. The monument is still clearly visible and easy to understand in the landscape.

The monument informs our understanding of a large and innovative scheme to manipulate the landscape to harness rainwater and to provide a water supply. The monument has the potential to further our understanding of the architecture and the construction techniques used to build the aqueduct, reservoir and associated sluices. The monument also has the capacity to further our knowledge of the way in which the system was designed to control and direct large volumes of water around the landscape using inter-related elements and the force of gravity. The duration of use of the monument, in excess of 150 years, means that the monument has the potential to retain information on the refinement and development of the system as technological advances were made, as well as illustrate the shortcomings of the system which led to its eventual abandonment.

Contextual characteristics

Water for Greenock was supplied by a number of wells and streams until a piped water supply was designed by James Watt and installed in 1773. However, Greenock expanded rapidly, with the population trebling between 1780 and 1820, and demand for water soon outstripped supply. The new system was designed to pipe water collected from the high ground to the south of the populated area. The Great Reservoir, Loch Thom, was the start of the aqueduct and the main source of water, but additional water was fed into the system as necessary from eight auxiliary reservoirs each located within its own valley and each connected directly to the aqueduct. The flow from the auxiliary reservoirs was controlled through innovative automatic sluices. The system had a capacity of 21,000 cubic feet of water per day and powered many industries in Greenock. The supply of domestic water was less successful until the construction of the Gryfe Reservoir in 1872.

In Greenock, the water was channelled through the town along two routes. At set levels along the length of these routes, sites, known as falls, were available for rent by water powered industries. These industries grew to include paper-making, distilling, textile, rope making, flour and sugar refining. Amongst these industries was the spinning works of Neil, Fleming, Reid and Co., where a water wheel in excess of 21.3m and known as the 'Great Wheel' operated. The remains of the lines of the falls can be seen at various locations in Greenock, as well as many of the former industrial buildings.

This is a rare type of industrial monument and there are few comparable systems for the organisation of water power in Scotland from this period. Thom's earlier scheme on Bute had canalised water from the south and west of the island to Loch Fad and then by lade to the sea and increased water power on the island from 30hp to 70hp, equivalent to steam power. It was on Bute that Thom designed self-activating sluices to lessen waste of water and also where he implemented auxiliary reservoirs to counteract periods of heavy rainfall. The contemporary 4-mile long Leven Cut in Fife was constructed with the dual aims of decreasing the levels of Loch Leven and thereby increasing agricultural land and also providing water power for mills and industries downstream. Comparison between these systems can increase our understanding of technological advancement.

Associative characteristics

The monument was designed by the hydraulic engineer, Robert Thom (1774-1847), at the height of the Industrial Revolution and its importance is enhanced by these associations. Thom was educated at the Andersonian Institute, Glasgow, and before working in Inverclyde worked on maximising power to the cotton mills of West Lothian and Rothesay, Bute. The principal reservoir of the Greenock Scheme is named after Thom. The Greenock scheme has been described as Thom's finest achievement, where he demonstrated his innovative thinking on water engineering. As an example of his work the monument has the capacity to further our understanding of hydraulic engineering and its development in Scotland and the contribution of Thom to that progress.

The monument is intimately linked to industrial progress and expansion in Greenock. It was the main conveyor of water to the town for over 150 years and its ability to satisfy the demand of a growing industry contributed to the success story of the town during this period.

The monument's importance is also enhanced by the survival of extensive documentation including maps and plans. These record details of the monument from its initial conception through to its use, adaption and abandonment. Robert Thom wrote of the scheme prior its approval: 'Here you would have no steam engines vomiting forth smoke and polluting earth and air for miles around; but on the contrary, the pure stream of the mountain flowing past in ceaseless profusion carrying along with it freshness, health and vigour'.

National Importance

The monument is of national importance because it has an inherent potential to make a significant addition to our understanding of the past, in particular to the study of hydraulic engineering and development of water provision for drinking and industry in 19th-century Greenock. The monument demonstrates the significant impact that technology had on the Scottish landscape during this period and the particular contribution of Robert Thom to hydraulic innovation. The well-preserved aqueduct, sluices and associated structures are an important survival of a defining period in industrial and civic history, not only in Inverclyde but across Scotland and further afield. The loss of the monument would impede our understanding of industrial development at a regional, national and international scale.

Source: Historic Environment Scotland



RCAHMS record this monument as NS27SW 24, 24.01 and NS27SE 54, 54.01, 54.02, 54.03. West of Scotland Archaeology Service Sites and Monuments Record use the identifier 14972 for the monument.


Clark, S 2008. The Shaws Water Falls in Greenock. In Renfrewshire Local History Forum Journal, Vol 14 pp26-31.

Lynn, James. 2005. Greenock Cut, PowerPoint Presentation

Inverclyde Council 2005. The Greenock Cut: The provider of opportunities for all its life. Maintenance Manual.

The Gazetteer for Scotland. Greenock Cut

Source: Historic Environment Scotland

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