WHEN I STAND beside the clear bubbling water of the river that flows through our farm, I look up to the hill where it rises, a rocky summit covered in heather and gorse. Here the water trickles from springs and boggy hollows to coalesce in several small streams that eventually form a single channel.
Generations of local farmers used the river to water their livestock and drained their wetter fields to ensure that the water ran more quickly down the slope. In times of heavy rainfall, the river becomes a raging torrent, carrying brown peaty water off the hill, down the valley and through the village.
The debris of fallen branches and leaves is washed downstream, gravel beds are washed clean of silt and the floods allow trout and salmon to move upstream to their traditional spawning grounds. It is likely that the river has been running here, just like this, since the last glaciers retreated many thousands of years ago. As Karine Polwart sang, ‘while kingdoms come and kingdoms go, rivers run and rivers flow’.
There is a legend that all the Irish rivers were created by a single hailstorm. It is an example of the mythology that surrounds many of our natural waterways, the rivers and lakes, streams and springs.
Even the names of Irish rivers have their origins in folklore. There are religious overtones too as the Goddesses of the Tuithe de Danann were worshipped as symbols of life while others derive from legendary characters such as Finn MacCool, the Fir Bolg and the Children of Lir.
The goddess Boen is the character after whom the River Boyne is named. The Shannon is named after the goddess Sionnan, granddaughter of Manannán Mac Lir the Son of the Sea. Sionnan means “possessor of wisdom”.
She is said to have eaten the Salmon of Knowledge and thus became the wisest person in the world. Whatever about the origin of these stories, the facts surrounding the real origins of the rivers are equally fascinating.
When you look at a map of Ireland showing all of the rivers, each one appears like a cluster of upturned tree roots with a massive and complicated network of channels. Moving upstream, the larger roots divide again and again into more and more tributaries so that the smallest streams are like the mass of fibrous roots that gather water for a tree.
These first- and second-order streams make up three-quarters of the river network with only about 85,000 kilometres of these smaller watercourses mapped so far. Tiny drainage ditches that do not feature on the map at all would probably double the total length of the channel.
Because of the saucer shape of the island most rivers, just like the one that flows through our farm, are relatively short, rising on coastal hills and mountain ranges and flowing directly to the sea. Those that flow across the relatively flat midland counties tend to be the longest rivers with the largest catchments.
The Shannon is by far the longest river network in Ireland with over 10,000 kilometres of measured channel. It can be claimed by eleven counties with rainwater landing on around one-seventh of the entire island flowing into it. Following the Shannon, the other most important rivers, in order of catchment size, are the Bann, Erne, Suir, Munster Blackwater, Corrib, Barrow, Foyle, Boyne, Nore and Slaney.
The most abundant forms of animal life in river water are the invertebrates (animals without backbones) that range in size from tiny organisms, visible only under a microscope, to large shellfish such as the freshwater pearl mussel.
Some invertebrates are found living on the beds of all types of rivers from fast-moving mountain streams tumbling over waterfalls to the slow-flowing, meandering stages of a mature watercourse. Turning over a large stone in the riverbed is the best way to see these.
Here you will find larval stages of caddisflies, stoneflies, mayflies, true flies and beetles, freshwater shrimps and crayfish, leeches and worms, as well as snails and freshwater shellfish. Some of these animals, such as the worms and molluscs, spend all of their lives in the water while the insect larvae will metamorphose into delicate winged adults that fly about laying eggs to produce the next generation.
The life in a river is directly related to the rock types over which it flows and the nature of the land in its catchment or watershed. Naturally, acidic rivers, such as those flowing off granite or quartzite are low in nutrients and support a limited range of animals. Their origins are often in open peatland habitats such as blanket bogs and wet heaths. These habitats soak up water at times of high rainfall and release it slowly during drier months in the same way that continental catchments store water as snow in winter and release it slowly in spring and summer as snow melt.
Lowland waters, winding through lime-rich lowlands, are often more alkaline in nature with abundant nutrients for all forms of animal life. This is the type of river on my own farm. It has been here for thousands of years and I hope it will remain for thousands of years after I am gone.
Richard Nairn is an ecologist and author. His new book Wild Waters is published by Gill Books.
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