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An introduction to the turloughs

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Turloughs are temporary water bodies that occur across central and western Ireland.
Carboniferous limestone is the dominant bedrock across these regions. In many areas this bedrock is exposed or has a very thin covering of soil.

Carboniferous limestone is easily dissolved by rainwater by a process known as karstification. Karstification can form an extensive network of grykes, underground caves and passage ways.

Rainfall passes through the limestone bedrock and flows through the subterranean drainage system. When the bedrock has become saturated with ground-water excess water is forced upwards to the surface. Water collects in depressions on the surface to form temporary water bodies known as turloughs.

The word turlough comes from the Irish "tuar loch" which means dry lake. If the water table drops the surface water drains underground leaving an empty depression where once there was a lake.

Turloughs empty through porous parts of the basin floor and also via connections to the groundwater known as swallow holes which often appear as small depressions filled with loose rocks.

The depth and duration of flooding can vary enormously between turloughs, these variations are due to differences in size, depth, and local ground water conditions. Soil composition is another important factor that results in the variation in the depth and duration of flooding between turloughs. The soils of turlough basins can be composed of sand, silt, clay, diamicton, peat or marl or as a combination of these types. Coxon (1986) derived associations with both duration and depth of inundation and soil composition. Diamicton, sand/silt and silt/ clay mixtures are associated with turloughs that have a short duration of flooding. Peat and marl types are associated with turloughs that have a longer duration of flooding. Turloughs with silt/clay or peat tend to be shallow (<1 m or 1-2 m).

Marl can be found in slightly deeper turloughs (2-3 m). The deposition of marl or calcite is due to the loss of CO₂ from water entering the turloughs which results in supersaturation and thus the deposition of calcite. The turlough waters are as a result very hard, this is reflected in high alkalinitiess and a pH that usually lies between 8 and 8.4.

Return to the top 'Turloughs an Irish phenomenon'

Turloughs are temporary water bodies that occur across central and western Ireland. Carboniferous limestone is the dominant bedrock across these regions. In many areas this bedrock is exposed or has a very thin covering of soil.
	Carboniferous limestone is easily dissolved by rainwater by a process known as karstification. Karstification can form an extensive network of grykes, underground caves and passage ways.
Rainfall passes through the limestone bedrock and flows through the subterranean drainage system. When the bedrock has become saturated with ground-water excess water is forced upwards to the surface. Water collects in depressions on the surface to form temporary water bodies known as turloughs.
	The word turlough comes from the Irish "tuar loch" which means dry lake. If the water table drops the surface water drains underground leaving an empty depression where once there was a lake.
Turloughs empty through porous parts of the basin floor and also via connections to the groundwater known as swallow holes which often appear as small depressions filled with loose rocks.