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In the hills high above the town of Greenock, in Scotland, there lies a body of water that played a vital role in the town’s history. Today it supplies the town and surrounding area with drinking water, but in the past, it was the powerhouse of the local industrial revolution. Loch Thom is not a natural loch, it is in fact man-made.

Towards the end of the 18th century, Greenock was a rapidly growing town and because of the increase in industry, there was also increasing demand for water power. James Watt was asked about the possibility of creating a new reservoir to improve the availability of water. The area in question was a depression in the landscape that already contained a small body of water. James Watt deemed this proposal impractical due to the route the aqueduct would need to take as it traversed the hillside towards town.

The same proposal was put to Robert Thom, a hydraulic engineer from the Isle of Bute. He accepted the proposal and constructed what would later become known as the Greenock Waterworks.

The project involved the creation of a large reservoir known as the Great Reservoir, its compensation dam and an aqueduct to channel the water towards the town. This aqueduct would become known as the Greenock Cut. The project was completed in 1827.

The Great Reservoir was created by damming off an existing waterway known as the Shaws Water. During a period of very low water, the banks of the former Shaws water became visible.

There is a belief that the Shaws Water was named after the Shaw family who were local landowners. It is more likely that the name was derived from a local farm known as Shaws. Its remains are still evident on the north bank of the Loch. There are also other farms and their remains dotted around the landscape.

Today the reservoir is used to supply the town of Greenock and the surrounding area with drinking water. In the 1970s a tunnel was blasted through the hillside to a new water treatment plant. Loch Thom stands as a lasting testament to what can be done when engineers set out to solve a problem. What started off as an idea… is now a local landmark.