Turlough (lake)
Encyclopedia
A turlough, or turlach, is a unique type of disappearing lake
found mostly in limestone
areas of Ireland
, west of the River Shannon
. The name comes from the Irish
"tuar", meaning dry, with the suffix "lach", meaning a place (in an abstract sense). The "lach" suffix is often mistakenly spelled and/or thought to refer to the word "loch", the Irish for lake. They are found in Irish karst
(exposed limestone) areas.
The features are almost unique to Ireland, although there is one example in Britain in Llandeilo
. They are of great interest to many scientists: geomorphologists
are interested in how turloughs were formed, hydrologists
try to explain what makes turloughs flood, botanists
study the unusual vegetation
which covers the turlough floor and zoologists
study the animals associated with the turloughs.
, Clare
, Mayo
and Roscommon
, although a few are also found elsewhere, e.g. in Limerick
, Sligo and Longford
.
Only three turloughs have been identified in Northern Ireland
, namely Roosky, Green and Fardrum Loughs located near Ely Lodge Forest in County Fermanagh
. These constitute the most northerly turloughs in Ireland and have been collectively designated a Ramsar site and an Area of Special Scientific Interest
.. There is one turlough in South Wales
, Pant y Llyn.
can flood at any time of year in a matter of a few hours after heavy rainfall and they may empty again a few days later.
Some turloughs are affected by the tide: in the summer, Caherglassaun Lough, situated 5 kilometres from Galway Bay
, can be seen to flood and empty again twice every 24 hours. Most turloughs flood to a depth of about 2 metres (6.6 ft) but some are much deeper: for example, some of the turloughs near Gort
reach about 5 metres (16.4 ft) deep in midwinter. Turloughs are variable in size: the largest turlough in Ireland, Rahasane turlough
, which lies to the west of Craughwell
in County Galway, covers about 2.5 square kilometre (0.965255396481338 sq mi).
ic by picking up carbon dioxide
as it passes through the atmosphere. The cracks or joints in the rock become widened to such an extent that eventually all of the rain falling on the limestone disappears underground and the water moves through the rock openings ranging from cracks a few millimetre
s wide to large cave
passages. The limestone is then said to be karstified.
To the east of the Shannon, the limestone is often covered by great thicknesses of glacial drift deposited during the Ice Age
but in many areas to the west of the Shannon where the limestone is pure and the drift cover is thin, there is no proper surface river
network. In these areas, rainfall disappears underground, flows through openings in the rock and then rises at springs
: large springs can be found to the west of the area, flowing into Lough Corrib
and Galway Bay
. In winter, when the underground water level (or water table
) rises, and when the underground flow rises, and when the underground flow routes to the springs are not capable of dealing with the amount of water entering them, groundwater may appear temporarily at the surface in the form of a turlough.
Many of the rivers seen in these areas today are largely artificial, constructed by drainage
engineer
s from the nineteenth century up to the present day, often linking a series of turloughs. For example, much of the River Clare
is artificial and the middle section of its course used to be a huge turlough, the largest in Ireland at 6.5 square kilometres (3 sq mi).
. Some turloughs have a spring at one place and a swallow hole (also known as a 'swallet') somewhere else on the floor where water drains away, but many turloughs fill and empty through the same hole. A few turloughs are filled by rivers and stream
s flowing into them as well as by water rising from underground.
The water sinking in the swallow hole travels underground to re-emerge at a spring, which may be several kilometres away. In most rock types, groundwater flows very slowly (from just a few centimetres to a few metres per day), but in karstified limestone the flow rate can be quite rapid: water from the turlough may flow underground to a spring at a rate of 100 metres per hour or more.
and as water passes through limestone, it dissolves the calcium carbonate - this is what makes hard water
and causes furring on the inside of kettle
s, as the calcium carbonate comes out of solution
when the water is heated. Something rather similar happens in turloughs - water that has picked up a lot of calcium carbonate during its underground travel rises in the turloughs and then some of the calcium carbonate comes out of solution and forms a white deposit. If a turlough has emptied recently, a whitish coating on the vegetation on the turlough floor may be visible. When water comes to the surface in a turlough, it loses carbon dioxide back to the atmosphere
and to plants, which use it for photosynthesis
, and this loss causes a deposit of calcium carbonate on the surface.
Sometimes a special whitish deposit with the appearance of sheets of paper is found in the turloughs when they dry up. This "algal paper" is made up of filaments of an alga that grows abundantly in warm weather and is then left to dry out in sheets when the turlough empties.
In drainage ditches in a turlough, or in holes made with a soil auger
, one may find a white- or cream-coloured deposit beneath the vegetation cover, or beneath a layer of peat
. This is often called "white marl
"; again, it is made of calcium carbonate. About half of the turloughs contain marl: it was deposited at a time several thousand years ago when these turloughs were not seasonal lakes but were flood
ed all year round.
of grass
es, sedge
s and herb
s. In the Burren, the highwater mark is often shown by the shrub
by cinquefoil with its attractive yellow flower
s, and meadow rue. Just below the highwater mark, dog violet
s are abundant and in some turloughs there may be a dense sward of the rare sky-blue turlough violet about one metre further down. Other characteristic plants of turlough sides include Marsh
orchids and speedwell
. About halfway down the sides, and across the bottom of shallow turloughs, silverweed may blanket almost all other plant
s.
If the turlough has a marsh
y zone near the swallow hole there may be mint
, water cress, pondweed
s, aquatic buttercups
and knotgrass
living a semiterrestrial existence. But most swallow holes when dry are represented by a jumble of rocks, clothed with blackish and dried aquatic moss
es .
Many people think that turloughs have no animal
life. However, frog
s and newt
s may spawn
there and sticklebacks may survive in the larger turloughs, retreating into underground cracks in the rock when waters are low. Shrimp
s and water lice do the same and where fish are absent there may be a rich fauna
of delicate water fleas and fairy shrimp
s, some unknown elsewhere in Ireland. These hatch and grow fast, finding safety in the warm fishless waters. Flatworm
s and snail
s are also often abundant; these pass the dry periods in spring mouths or marshy areas.
When turloughs retain some water all year, they may be important bird
haunts. Rahasane in Galway is famous for its white-fronted geese
, whooper swan
s, widgeon, teal
and many waders in winter.
for cattle
, sheep and horse
s, partly because of the annual deposition of lime-rich silt
. However, for many years, farmer
s have seen the winter flooding as a waste of potential and they have attempted to find some means of draining the turloughs so that they can be used all year round. This has usually been achieved by digging an artificial channel through the turlough, capable of carrying away any water entering the turlough from surface or groundwater – such channels have often been constructed as part of major arterial drainage schemes.
At least a third of the turloughs in Ireland have already been drained and more are being drained each year. This has very serious consequences from the point of view of the environmentalist
– the unique flora and fauna of the turlough cannot survive in the absence of seasonal flooding. Even for the farmer, the benefits are not always as great as anticipated – the stopping of the annual limy silt deposition means that the soil may become impoverished and fertilisers must be used. Also, the poorly developed and delicate soil may not be able to withstand the presence of animals through the winter.
Lake
A lake is a body of relatively still fresh or salt water of considerable size, localized in a basin, that is surrounded by land. Lakes are inland and not part of the ocean and therefore are distinct from lagoons, and are larger and deeper than ponds. Lakes can be contrasted with rivers or streams,...
found mostly in limestone
Limestone
Limestone is a sedimentary rock composed largely of the minerals calcite and aragonite, which are different crystal forms of calcium carbonate . Many limestones are composed from skeletal fragments of marine organisms such as coral or foraminifera....
areas of Ireland
Ireland
Ireland is an island to the northwest of continental Europe. It is the third-largest island in Europe and the twentieth-largest island on Earth...
, west of the River Shannon
River Shannon
The River Shannon is the longest river in Ireland at . It divides the west of Ireland from the east and south . County Clare, being west of the Shannon but part of the province of Munster, is the major exception...
. The name comes from the Irish
Irish language
Irish , also known as Irish Gaelic, is a Goidelic language of the Indo-European language family, originating in Ireland and historically spoken by the Irish people. Irish is now spoken as a first language by a minority of Irish people, as well as being a second language of a larger proportion of...
"tuar", meaning dry, with the suffix "lach", meaning a place (in an abstract sense). The "lach" suffix is often mistakenly spelled and/or thought to refer to the word "loch", the Irish for lake. They are found in Irish karst
KARST
Kilometer-square Area Radio Synthesis Telescope is a Chinese telescope project to which FAST is a forerunner. KARST is a set of large spherical reflectors on karst landforms, which are bowlshaped limestone sinkholes named after the Kras region in Slovenia and Northern Italy. It will consist of...
(exposed limestone) areas.
The features are almost unique to Ireland, although there is one example in Britain in Llandeilo
Llandeilo
Llandeilo is a town in Carmarthenshire, Wales, situated at the crossing of the River Towy by the A483 on a 19th century stone bridge. Its population is 1,731.The town is served by Llandeilo railway station on the Heart of Wales Line.- Early history :...
. They are of great interest to many scientists: geomorphologists
Geomorphology
Geomorphology is the scientific study of landforms and the processes that shape them...
are interested in how turloughs were formed, hydrologists
Hydrology
Hydrology is the study of the movement, distribution, and quality of water on Earth and other planets, including the hydrologic cycle, water resources and environmental watershed sustainability...
try to explain what makes turloughs flood, botanists
Botany
Botany, plant science, or plant biology is a branch of biology that involves the scientific study of plant life. Traditionally, botany also included the study of fungi, algae and viruses...
study the unusual vegetation
Vegetation
Vegetation is a general term for the plant life of a region; it refers to the ground cover provided by plants. It is a general term, without specific reference to particular taxa, life forms, structure, spatial extent, or any other specific botanical or geographic characteristics. It is broader...
which covers the turlough floor and zoologists
Zoology
Zoology |zoölogy]]), is the branch of biology that relates to the animal kingdom, including the structure, embryology, evolution, classification, habits, and distribution of all animals, both living and extinct...
study the animals associated with the turloughs.
Locations
Turloughs are mostly found on the central lowlands west of the Shannon, in counties GalwayCounty Galway
County Galway is a county in Ireland. It is located in the West Region and is also part of the province of Connacht. It is named after the city of Galway. Galway County Council is the local authority for the county. There are several strongly Irish-speaking areas in the west of the county...
, Clare
County Clare
-History:There was a Neolithic civilisation in the Clare area — the name of the peoples is unknown, but the Prehistoric peoples left evidence behind in the form of ancient dolmen; single-chamber megalithic tombs, usually consisting of three or more upright stones...
, Mayo
County Mayo
County Mayo is a county in Ireland. It is located in the West Region and is also part of the province of Connacht. It is named after the village of Mayo, which is now generally known as Mayo Abbey. Mayo County Council is the local authority for the county. The population of the county is 130,552...
and Roscommon
County Roscommon
County Roscommon is a county in Ireland. It is located in the West Region and is also part of the province of Connacht. It is named after the town of Roscommon. Roscommon County Council is the local authority for the county...
, although a few are also found elsewhere, e.g. in Limerick
County Limerick
It is thought that humans had established themselves in the Lough Gur area of the county as early as 3000 BC, while megalithic remains found at Duntryleague date back further to 3500 BC...
, Sligo and Longford
County Longford
County Longford is a county in Ireland. It is part of the Midlands Region and is also located in the province of Leinster. It is named after the town of Longford.Longford County Council is the local authority for the county...
.
Only three turloughs have been identified in Northern Ireland
Northern Ireland
Northern Ireland is one of the four countries of the United Kingdom. Situated in the north-east of the island of Ireland, it shares a border with the Republic of Ireland to the south and west...
, namely Roosky, Green and Fardrum Loughs located near Ely Lodge Forest in County Fermanagh
County Fermanagh
Fermanagh District Council is the only one of the 26 district councils in Northern Ireland that contains all of the county it is named after. The district council also contains a small section of County Tyrone in the Dromore and Kilskeery road areas....
. These constitute the most northerly turloughs in Ireland and have been collectively designated a Ramsar site and an Area of Special Scientific Interest
Area of Special Scientific Interest
An Area of Special Scientific Interest or ASSI is a conservation designation denoting a protected area in Northern Ireland. ASSIs are the equivalent of Sites of Special Scientific Interest in the rest of the United Kingdom....
.. There is one turlough in South Wales
South Wales
South Wales is an area of Wales bordered by England and the Bristol Channel to the east and south, and Mid Wales and West Wales to the north and west. The most densely populated region in the south-west of the United Kingdom, it is home to around 2.1 million people and includes the capital city of...
, Pant y Llyn.
Seasonal pools
Most turloughs flood in the autumn, usually some time in October, and then dry up some time between April and July. However, some turloughs in the BurrenThe Burren
The Burren is a karst-landscape region or alvar in northwest County Clare, in Ireland. It is one of the largest karst landscapes in Europe. The region measures approximately 250 square kilometres and is enclosed roughly within the circle made by the villages Ballyvaughan, Kinvara, Tubber, Corofin,...
can flood at any time of year in a matter of a few hours after heavy rainfall and they may empty again a few days later.
Some turloughs are affected by the tide: in the summer, Caherglassaun Lough, situated 5 kilometres from Galway Bay
Galway Bay
Galway Bay is a large bay on the west coast of Ireland, between County Galway in the province of Connacht to the north and the Burren in County Clare in the province of Munster to the south. Galway city is located on the northeast side of the bay. It is about long and from to in breadth...
, can be seen to flood and empty again twice every 24 hours. Most turloughs flood to a depth of about 2 metres (6.6 ft) but some are much deeper: for example, some of the turloughs near Gort
Gort
Gort is a town in south County Galway in the west of Ireland. An Gort is the official Irish name for the town, as defined by the Placenames Commission. In spoken Irish, however, the town is known by its traditional name Gort Inse Guaire. It lies just north of the border with County Clare on the...
reach about 5 metres (16.4 ft) deep in midwinter. Turloughs are variable in size: the largest turlough in Ireland, Rahasane turlough
Rahasane turlough
Rahasane turlough is a turlough, that is a karst lake, which has no surface outlet and is surrounded on all sides by rising land. It is the largest surviving turlough in Ireland. Water collects seasonally in the basin and drains away only through evaporation or seepage into the underlying limestone...
, which lies to the west of Craughwell
Craughwell
Craughwell is a village and townland in County Galway, Republic of Ireland. The name is also used as a surname, properly Ó Creachmhaoil, though often anglicised as Craughwell and Crockwell...
in County Galway, covers about 2.5 square kilometre (0.965255396481338 sq mi).
Formation
All of the turloughs are found in limestone areas. This is because limestone can be dissolved away by rainwater, which becomes mildly acidAcid
An acid is a substance which reacts with a base. Commonly, acids can be identified as tasting sour, reacting with metals such as calcium, and bases like sodium carbonate. Aqueous acids have a pH of less than 7, where an acid of lower pH is typically stronger, and turn blue litmus paper red...
ic by picking up carbon dioxide
Carbon dioxide
Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...
as it passes through the atmosphere. The cracks or joints in the rock become widened to such an extent that eventually all of the rain falling on the limestone disappears underground and the water moves through the rock openings ranging from cracks a few millimetre
Millimetre
The millimetre is a unit of length in the metric system, equal to one thousandth of a metre, which is the SI base unit of length....
s wide to large cave
Cave
A cave or cavern is a natural underground space large enough for a human to enter. The term applies to natural cavities some part of which is in total darkness. The word cave also includes smaller spaces like rock shelters, sea caves, and grottos.Speleology is the science of exploration and study...
passages. The limestone is then said to be karstified.
To the east of the Shannon, the limestone is often covered by great thicknesses of glacial drift deposited during the Ice Age
Ice age
An ice age or, more precisely, glacial age, is a generic geological period of long-term reduction in the temperature of the Earth's surface and atmosphere, resulting in the presence or expansion of continental ice sheets, polar ice sheets and alpine glaciers...
but in many areas to the west of the Shannon where the limestone is pure and the drift cover is thin, there is no proper surface river
River
A river is a natural watercourse, usually freshwater, flowing towards an ocean, a lake, a sea, or another river. In a few cases, a river simply flows into the ground or dries up completely before reaching another body of water. Small rivers may also be called by several other names, including...
network. In these areas, rainfall disappears underground, flows through openings in the rock and then rises at springs
Spring (hydrosphere)
A spring—also known as a rising or resurgence—is a component of the hydrosphere. Specifically, it is any natural situation where water flows to the surface of the earth from underground...
: large springs can be found to the west of the area, flowing into Lough Corrib
Lough Corrib
Lough Corrib is a lake in the west of Ireland. The River Corrib or Galway river connects the lake to the sea at Galway. It is the second largest lough in Ireland . It covers 178 km² and lies mostly in County Galway with a small area of its northeast corner in County Mayo.The first canal in...
and Galway Bay
Galway Bay
Galway Bay is a large bay on the west coast of Ireland, between County Galway in the province of Connacht to the north and the Burren in County Clare in the province of Munster to the south. Galway city is located on the northeast side of the bay. It is about long and from to in breadth...
. In winter, when the underground water level (or water table
Water table
The water table is the level at which the submarine pressure is far from atmospheric pressure. It may be conveniently visualized as the 'surface' of the subsurface materials that are saturated with groundwater in a given vicinity. However, saturated conditions may extend above the water table as...
) rises, and when the underground flow rises, and when the underground flow routes to the springs are not capable of dealing with the amount of water entering them, groundwater may appear temporarily at the surface in the form of a turlough.
Many of the rivers seen in these areas today are largely artificial, constructed by drainage
Drainage
Drainage is the natural or artificial removal of surface and sub-surface water from an area. Many agricultural soils need drainage to improve production or to manage water supplies.-Early history:...
engineer
Engineer
An engineer is a professional practitioner of engineering, concerned with applying scientific knowledge, mathematics and ingenuity to develop solutions for technical problems. Engineers design materials, structures, machines and systems while considering the limitations imposed by practicality,...
s from the nineteenth century up to the present day, often linking a series of turloughs. For example, much of the River Clare
River Clare
The River Clare is a river in counties Mayo and Galway in Ireland. The long river rises north of Ballyhaunis in Mayo and descends past Dunmore, where it flows west, then turns south past Milltown, continuing down through Kilbennan Church near Tuam...
is artificial and the middle section of its course used to be a huge turlough, the largest in Ireland at 6.5 square kilometres (3 sq mi).
Swallow holes
Turloughs usually fill and empty at particular places on the floor: sometimes an actual hole or passage is visible but more often a hollow with stones in the bottom is all that can be seen and it may not be easy to recognise when it is dry in midsummerMidsummer
Midsummer may simply refer to the period of time centered upon the summer solstice, but more often refers to specific European celebrations that accompany the actual solstice, or that take place on a day between June 21 and June 24, and the preceding evening. The exact dates vary between different...
. Some turloughs have a spring at one place and a swallow hole (also known as a 'swallet') somewhere else on the floor where water drains away, but many turloughs fill and empty through the same hole. A few turloughs are filled by rivers and stream
Stream
A stream is a body of water with a current, confined within a bed and stream banks. Depending on its locale or certain characteristics, a stream may be referred to as a branch, brook, beck, burn, creek, "crick", gill , kill, lick, rill, river, syke, bayou, rivulet, streamage, wash, run or...
s flowing into them as well as by water rising from underground.
The water sinking in the swallow hole travels underground to re-emerge at a spring, which may be several kilometres away. In most rock types, groundwater flows very slowly (from just a few centimetres to a few metres per day), but in karstified limestone the flow rate can be quite rapid: water from the turlough may flow underground to a spring at a rate of 100 metres per hour or more.
Calcium carbonate deposits
Limestone is made up of the mineral calcium carbonateCalcium carbonate
Calcium carbonate is a chemical compound with the formula CaCO3. It is a common substance found in rocks in all parts of the world, and is the main component of shells of marine organisms, snails, coal balls, pearls, and eggshells. Calcium carbonate is the active ingredient in agricultural lime,...
and as water passes through limestone, it dissolves the calcium carbonate - this is what makes hard water
Hard water
Hard water is water that has high mineral content . Hard water has high concentrations of Ca2+ and Mg2+ ions. Hard water is generally not harmful to one's health but can pose serious problems in industrial settings, where water hardness is monitored to avoid costly breakdowns in boilers, cooling...
and causes furring on the inside of kettle
Kettle
A kettle, sometimes called a tea kettle or teakettle, is a small kitchen appliance used for boiling water. Kettles can be heated either by placing on a stove, or by their own electric heating element.- Stovetop kettles :...
s, as the calcium carbonate comes out of solution
Solution
In chemistry, a solution is a homogeneous mixture composed of only one phase. In such a mixture, a solute is dissolved in another substance, known as a solvent. The solvent does the dissolving.- Types of solutions :...
when the water is heated. Something rather similar happens in turloughs - water that has picked up a lot of calcium carbonate during its underground travel rises in the turloughs and then some of the calcium carbonate comes out of solution and forms a white deposit. If a turlough has emptied recently, a whitish coating on the vegetation on the turlough floor may be visible. When water comes to the surface in a turlough, it loses carbon dioxide back to the atmosphere
Atmosphere
An atmosphere is a layer of gases that may surround a material body of sufficient mass, and that is held in place by the gravity of the body. An atmosphere may be retained for a longer duration, if the gravity is high and the atmosphere's temperature is low...
and to plants, which use it for photosynthesis
Photosynthesis
Photosynthesis is a chemical process that converts carbon dioxide into organic compounds, especially sugars, using the energy from sunlight. Photosynthesis occurs in plants, algae, and many species of bacteria, but not in archaea. Photosynthetic organisms are called photoautotrophs, since they can...
, and this loss causes a deposit of calcium carbonate on the surface.
Sometimes a special whitish deposit with the appearance of sheets of paper is found in the turloughs when they dry up. This "algal paper" is made up of filaments of an alga that grows abundantly in warm weather and is then left to dry out in sheets when the turlough empties.
In drainage ditches in a turlough, or in holes made with a soil auger
Auger
An auger is a drilling device, or drill bit, that usually includes a rotating helical screw blade called a "flighting" to act as a screw conveyor to remove the drilled out material...
, one may find a white- or cream-coloured deposit beneath the vegetation cover, or beneath a layer of peat
Peat
Peat is an accumulation of partially decayed vegetation matter or histosol. Peat forms in wetland bogs, moors, muskegs, pocosins, mires, and peat swamp forests. Peat is harvested as an important source of fuel in certain parts of the world...
. This is often called "white marl
Marl
Marl or marlstone is a calcium carbonate or lime-rich mud or mudstone which contains variable amounts of clays and aragonite. Marl was originally an old term loosely applied to a variety of materials, most of which occur as loose, earthy deposits consisting chiefly of an intimate mixture of clay...
"; again, it is made of calcium carbonate. About half of the turloughs contain marl: it was deposited at a time several thousand years ago when these turloughs were not seasonal lakes but were flood
Flood
A flood is an overflow of an expanse of water that submerges land. The EU Floods directive defines a flood as a temporary covering by water of land not normally covered by water...
ed all year round.
Plant and animal life
Most turloughs have a springy, short-cropped turfSod
Sod or turf is grass and the part of the soil beneath it held together by the roots, or a piece of thin material.The term sod may be used to mean turf grown and cut specifically for the establishment of lawns...
of grass
Grass
Grasses, or more technically graminoids, are monocotyledonous, usually herbaceous plants with narrow leaves growing from the base. They include the "true grasses", of the Poaceae family, as well as the sedges and the rushes . The true grasses include cereals, bamboo and the grasses of lawns ...
es, sedge
Cyperaceae
Cyperaceae are a family of monocotyledonous graminoid flowering plants known as sedges, which superficially resemble grasses or rushes. The family is large, with some 5,500 species described in about 109 genera. These species are widely distributed, with the centers of diversity for the group...
s and herb
Herb
Except in botanical usage, an herb is "any plant with leaves, seeds, or flowers used for flavoring, food, medicine, or perfume" or "a part of such a plant as used in cooking"...
s. In the Burren, the highwater mark is often shown by the shrub
Shrub
A shrub or bush is distinguished from a tree by its multiple stems and shorter height, usually under 5–6 m tall. A large number of plants may become either shrubs or trees, depending on the growing conditions they experience...
by cinquefoil with its attractive yellow flower
Flower
A flower, sometimes known as a bloom or blossom, is the reproductive structure found in flowering plants . The biological function of a flower is to effect reproduction, usually by providing a mechanism for the union of sperm with eggs...
s, and meadow rue. Just below the highwater mark, dog violet
Dog violet
Dog violet is the common name for various species of the plant genus Viola with unscented flowers. The term arose to differentiate them from the scented sweet violet. Species so named include:*Viola canina - heath dog violet...
s are abundant and in some turloughs there may be a dense sward of the rare sky-blue turlough violet about one metre further down. Other characteristic plants of turlough sides include Marsh
Dactylorhiza
Dactylorhiza , is a genus of terrestrial plants in the orchid family ....
orchids and speedwell
Veronica (plant)
Veronica is the largest genus in the flowering plant family Plantaginaceae, with about 500 species; it was formerly classified in the family Scrophulariaceae...
. About halfway down the sides, and across the bottom of shallow turloughs, silverweed may blanket almost all other plant
Plant
Plants are living organisms belonging to the kingdom Plantae. Precise definitions of the kingdom vary, but as the term is used here, plants include familiar organisms such as trees, flowers, herbs, bushes, grasses, vines, ferns, mosses, and green algae. The group is also called green plants or...
s.
If the turlough has a marsh
Marsh
In geography, a marsh, or morass, is a type of wetland that is subject to frequent or continuous flood. Typically the water is shallow and features grasses, rushes, reeds, typhas, sedges, other herbaceous plants, and moss....
y zone near the swallow hole there may be mint
Mentha
Mentha is a genus of flowering plants in the family Lamiaceae . The species are not clearly distinct and estimates of the number of species varies from 13 to 18. Hybridization between some of the species occurs naturally...
, water cress, pondweed
Pondweed
Pondweed refers to many species and genera of aquatic plants and green algae:*Potamogeton, a diverse and worldwide genus*Elodea, found in North America*Aponogeton, in Africa, Asia and Australasia*Groenlandia, a genus of aquatic plants...
s, aquatic buttercups
Ranunculus flammula
Ranunculus flammula L. is a species of perennial herbaceous plants in the genus Ranunculus , growing in damp places throughout the Boreal Kingdom. It is very closely related to R. reptans L., which is distinguished by prostrate and more slender stems, narrower leaves and smaller flowers and is...
and knotgrass
Polygonum
Polygonum is a genus in the Polygonaceae family. Common names include knotweed, knotgrass, bistort, tear-thumb, mile-a-minute, and several others. In the Middle English glossary of herbs "Alphita" , it was known as ars-smerte. There have been various opinions about how broadly the genus should be...
living a semiterrestrial existence. But most swallow holes when dry are represented by a jumble of rocks, clothed with blackish and dried aquatic moss
Moss
Mosses are small, soft plants that are typically 1–10 cm tall, though some species are much larger. They commonly grow close together in clumps or mats in damp or shady locations. They do not have flowers or seeds, and their simple leaves cover the thin wiry stems...
es .
Many people think that turloughs have no animal
Animal
Animals are a major group of multicellular, eukaryotic organisms of the kingdom Animalia or Metazoa. Their body plan eventually becomes fixed as they develop, although some undergo a process of metamorphosis later on in their life. Most animals are motile, meaning they can move spontaneously and...
life. However, frog
Frog
Frogs are amphibians in the order Anura , formerly referred to as Salientia . Most frogs are characterized by a short body, webbed digits , protruding eyes and the absence of a tail...
s and newt
Newt
A newt is an aquatic amphibian of the family Salamandridae, although not all aquatic salamanders are considered newts. Newts are classified in the subfamily Pleurodelinae of the family Salamandridae, and are found in North America, Europe and Asia...
s may spawn
Spawn (biology)
Spawn refers to the eggs and sperm released or deposited, usually into water, by aquatic animals. As a verb, spawn refers to the process of releasing the eggs and sperm, also called spawning...
there and sticklebacks may survive in the larger turloughs, retreating into underground cracks in the rock when waters are low. Shrimp
Shrimp
Shrimp are swimming, decapod crustaceans classified in the infraorder Caridea, found widely around the world in both fresh and salt water. Adult shrimp are filter feeding benthic animals living close to the bottom. They can live in schools and can swim rapidly backwards. Shrimp are an important...
s and water lice do the same and where fish are absent there may be a rich fauna
Fauna
Fauna or faunæ is all of the animal life of any particular region or time. The corresponding term for plants is flora.Zoologists and paleontologists use fauna to refer to a typical collection of animals found in a specific time or place, e.g. the "Sonoran Desert fauna" or the "Burgess shale fauna"...
of delicate water fleas and fairy shrimp
Fairy shrimp
Anostraca is one of the four orders of crustaceans in the class Branchiopoda; its members are also known as fairy shrimp. They are usually long . Most species have 20 body segments, bearing 11 pairs of leaf-like phyllopodia , and the body lacks a carapace...
s, some unknown elsewhere in Ireland. These hatch and grow fast, finding safety in the warm fishless waters. Flatworm
Flatworm
The flatworms, known in scientific literature as Platyhelminthes or Plathelminthes are a phylum of relatively simple bilaterian, unsegmented, soft-bodied invertebrate animals...
s and snail
Snail
Snail is a common name applied to most of the members of the molluscan class Gastropoda that have coiled shells in the adult stage. When the word is used in its most general sense, it includes sea snails, land snails and freshwater snails. The word snail without any qualifier is however more often...
s are also often abundant; these pass the dry periods in spring mouths or marshy areas.
When turloughs retain some water all year, they may be important bird
Bird
Birds are feathered, winged, bipedal, endothermic , egg-laying, vertebrate animals. Around 10,000 living species and 188 families makes them the most speciose class of tetrapod vertebrates. They inhabit ecosystems across the globe, from the Arctic to the Antarctic. Extant birds range in size from...
haunts. Rahasane in Galway is famous for its white-fronted geese
White-fronted Goose
The Greater White-fronted Goose is a species of goose. The Greater White-fronted Goose is more closely related to the smaller Lesser White-fronted Goose...
, whooper swan
Whooper Swan
The Whooper Swan , Cygnus cygnus, is a large Northern Hemisphere swan. It is the Eurasian counterpart of the North American Trumpeter Swan. An old name for the Whooper Swan is Elk; it is so called in Francis Willughby and John Ray's Ornithology of 1676.-Description:The Whooper Swan is similar in...
s, widgeon, teal
Teal
Teal may mean:* Teal , a medium greenish-blue color* Various ducks:** Baikal Teal, Anas formosa** Black Teal, Aythya novaeseelandiae** Blue-winged Teal, Anas discors** Brown Teal, Anas aucklandica** Campbell Teal Anas nesiotis...
and many waders in winter.
Draining of turloughs
Turloughs provide good summer grazingGrazing
Grazing generally describes a type of feeding, in which a herbivore feeds on plants , and also on other multicellular autotrophs...
for cattle
Cattle
Cattle are the most common type of large domesticated ungulates. They are a prominent modern member of the subfamily Bovinae, are the most widespread species of the genus Bos, and are most commonly classified collectively as Bos primigenius...
, sheep and horse
Horse
The horse is one of two extant subspecies of Equus ferus, or the wild horse. It is a single-hooved mammal belonging to the taxonomic family Equidae. The horse has evolved over the past 45 to 55 million years from a small multi-toed creature into the large, single-toed animal of today...
s, partly because of the annual deposition of lime-rich silt
Silt
Silt is granular material of a size somewhere between sand and clay whose mineral origin is quartz and feldspar. Silt may occur as a soil or as suspended sediment in a surface water body...
. However, for many years, farmer
Farmer
A farmer is a person engaged in agriculture, who raises living organisms for food or raw materials, generally including livestock husbandry and growing crops, such as produce and grain...
s have seen the winter flooding as a waste of potential and they have attempted to find some means of draining the turloughs so that they can be used all year round. This has usually been achieved by digging an artificial channel through the turlough, capable of carrying away any water entering the turlough from surface or groundwater – such channels have often been constructed as part of major arterial drainage schemes.
At least a third of the turloughs in Ireland have already been drained and more are being drained each year. This has very serious consequences from the point of view of the environmentalist
Environmental movement
The environmental movement, a term that includes the conservation and green politics, is a diverse scientific, social, and political movement for addressing environmental issues....
– the unique flora and fauna of the turlough cannot survive in the absence of seasonal flooding. Even for the farmer, the benefits are not always as great as anticipated – the stopping of the annual limy silt deposition means that the soil may become impoverished and fertilisers must be used. Also, the poorly developed and delicate soil may not be able to withstand the presence of animals through the winter.
Further reading
- National Parks and Wildlife Service (c. 1980) Wetlands Discovered. (Available from Duchas, National Parks and Wildlife Service)
- O'Gorman, F. (1979) The Irish Wildlife Book, Irish Wildlife Publications, Dublin. (pages 58–60)
- Praeger, R. Lloyd (1950) The Natural History of Ireland, Collins, Ireland.
- Webb, D.A. & Scannell, M. (1983) Flora of Connemara and the Burren. Royal Dublin Society, Cambridge.