Turloughs and Meres

(Aquifer Fed Naturally Fluctuating Water Bodies)

What are they?

These habitats are immensely rare in the UK, with a total extent of approximately 31ha. They are the turloughs of Ireland (with one in South Wales), and the fluctuating meres of Norfolk Breckland. These wetlands experience extreme fluctuations in water levels, with periods of complete or almost complete drying out as part of the natural cycle. They have no inflow or outflow streams at the surface, except at times of very high water level, when temporary out-flows may develop. Instead, they are directly connected to the underlying groundwater system and periodically empty and are recharged via swallow holes or smaller openings in their beds.

There are two known variants of the habitat in the UK: Turloughs, found over Carboniferous limestone in Northern Ireland and Wales, and fluctuating Meres, which occur over chalk in the Norfolk Breckland. The water level in both turloughs and meres reflects the height of the water table, which periodically rises above the surface of the bed. The response to groundwater fluctuations in turloughs is rapid, whereas that in the meres has a longer time lag. 

What’s special about them?

These habitats may be very important for great crested newts. They also support highly mobile species such as dragonflies and diving beetles, which can colonise new water bodies rapidly. When flooded, they are used by tufted duck, pochard and gadwall.

How do we benefit?

Turloughs and meres are so rare that they are of intrinsic value for their specially adapted wildlife and because of their fascinating geology and hydrology.

How could development affect them?

They are generally protected wherever they occur, and need to be buffered from the effects of intensive agriculture, water abstraction and development.

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UKBAP list of priority habitats