Qualla: Silent Valley Reservoir

Silent Valley Reservoir: Introduction

Sun, 24 May 2026 00:00:00 GMT

Photo credit Ryan Mcdonald, CC BY 2.0. It took ten years and over a thousand men to make a valley into a lake. Between 1923 and 1933, in a fold of the Mourne Mountains near Kilkeel, workers raised an earth-and-concrete dam across the Kilkeel River and filled the basin behind it with mountain rainwater. Nine of them died in the doing. The reservoir they left behind, the Silent Valley, still supplies most of the drinking water for Belfast and the eastern half of Northern Ireland. Walk to the dam wall today and the loudest sound is wind off Slieve Binnian. The name fits.

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Image: Ryan Mcdonald | CC BY 2.0

Silent Valley Reservoir: Why the Mournes

Sun, 24 May 2026 00:00:00 GMT

Photo credit CC BY-SA 3.0. Belfast was growing fast in the 1890s and running out of clean water. In 1891 the Belfast Water Commissioners hired an engineer named Luke Livingston Macassey to find a solution, and he looked south to the Mournes. A 1935 report explained what he found: roughly 9,000 acres of uni...

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Image: CC BY-SA 3.0

Silent Valley Reservoir: The Mourne Wall

Sun, 24 May 2026 00:00:00 GMT

Photo credit Ryan Mcdonald, CC BY 2.0. Before the dam came the wall. Starting in 1904, masons began building a six-foot-high drystone wall around the entire 9,000-acre catchment, marking the boundary the Water Commissioners had purchased and keeping livestock from polluting the streams. It took eighteen years to compl...

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Image: Ryan Mcdonald | CC BY 2.0

Silent Valley Reservoir: Ten Years in the Valley

Sun, 24 May 2026 00:00:00 GMT

Photo credit Mick Garratt, CC BY-SA 2.0. The original plan called for a quick conventional dam. The valley refused. The bedrock turned out to be deeply buried under glacial debris, and engineers had to dig down 200 feet before they found rock solid enough to build on. The dam wall, when it finally rose, contained 145,00...

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Image: Mick Garratt | CC BY-SA 2.0

Silent Valley Reservoir: The Tunnel Under Slieve Binnian

Sun, 24 May 2026 00:00:00 GMT

Photo credit Chris Allen, CC BY-SA 2.0. Even with the new reservoir, Belfast kept growing and kept thirsty. A second dam in the neighbouring Annalong valley had been planned but was judged too difficult after the Silent Valley experience. Instead, between 1947 and 1951, more than 150 men drove a tunnel straight through...

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Image: Chris Allen | CC BY-SA 2.0

Silent Valley Reservoir: What the Silence Is Made Of

Sun, 24 May 2026 00:00:00 GMT

Photo credit Trevor Caruth (Uploaded by Johnnykimble), CC BY-SA 3.0. Stand on the dam wall on a still morning and the surface mirrors the granite peaks above. Wind ruffles the water without much noise. There are no boats, no swimming, no shouting children. The reservoir is a working piece of infrastructure, fenced and protected. The visitor's cent...

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Image: Trevor Caruth (Uploaded by Johnnykimble) | CC BY-SA 3.0