Dublin once had a grand total of over 60 streams and rivers that flowed entirely above ground. Today, most of those rivers and streams have disappeared from view, forced underground as the city has expanded, so that they have largely vanished from the public consciousness.
The Liffey, the Dodder, the Santry River and the Tolka are among the few that remain uncovered.
One person with a lifelong knowledge of Dublin watercourses is Michael Corcoran, who still works part-time, for the drainage department in Dublin City Council. He has worked in Dublin local government since 1947 and claims, with a knowing smile, to have been the oldest person in the Corporation to have become computer literate. His great knowledge of the city's rivers gives an unusual perspective on Dublin's history and buildings.
His book on the subject, Your Good Health, is being published by the city council in time for Christmas. Next month, he will give the last in a series of talks in City Hall examining the epidemics that once plagued the city. The development of the city' s drainage system did much to make the city a healthier place in which to live.
Michael Corcoran explains that Dublin's very first water supply came from the River Poddle, back in the mid-13th century. In the late 18th century, much of the city's drinking water was drawn from the canals, until they became too polluted. By the 19th century, the Poddle had become an open sewer, although it is not in such a bad state nowadays.
The Poddle rises at Cookstown in Tallaght and eventually flows into the Liffey near Grattan bridge. Upstream of Kimmage, it is known as the Tymon River.
About 15 watercourses are connected with the Poddle, including the wonderfully named Glib River and the Tenter Water in the Tenters' district.
The Poddle flows underground beside Dublin Castle, and a branch of it rushes beneath the Olympia Theatre in Dame Street. Another river that was much cleaned up is the Camac, to the west of the city; once, it was heavily polluted by the old paper mills in the Clondalkin area.
These days, you can still see parts of the Poddle in places such as Kimmage, while the Camac is also visible in parts of Inchicore.
But one well-known river on the southside has totally disappeared from view - the Swan, which drains Terenure, Rathmines and Ballsbridge. These days, the only remembrance of the Swan is in name of the local shopping centre in Rathmines. The Swan flows underground beneath Morehampton Road and Clyde Road and eventually falls into the River Dodder near Londonbridge Road. One branch of it flowed into the Dodder near the bridge at Ballsbridge after passing through what is now Herbert Park. For generations of schoolchildren going up to Muckross convent school, it was known as the "Swanee" .
Other streams on the southside can still be seen, however, such as the Elm Park stream and the Nutley stream. The underground part of the Nutley stream runs beneath the RTE studios in Donnybrook.
The northside has an abundance of rivers and streams, such as the Tolka, still a surface river. Its numerous tributaries include the Finglas River, the Wad River in Donnycarney, the Grace Park Stream and the Hampstead Stream. Some of the northside rivers have vanished from view, such as the Naniken in Beaumont, which drains to the sea near North Bull Island. It took its name from the Nanny River, which flows into the sea at Laytown, Co Meath and which is three times bigger than the river in Dublin. The suffix "iken" means small.
The hill of Howth has a whole complex of streams while the Phoenix Park has three main ones, the Magazine Stream, the Vice-Regal Stream and the Furry Glen Stream.
Underneath the city centre, several streams and rivers run in channels far below the surface. The Stein River starts near Charlemont Mall canal bridge, flows beneath the south side of St Stephen's Green, then under Clarendon Street and eventually empties into the Liffey.
The Gallows Stream, which flows close to Government Buildings, is a modest affair, starting near Leeson Lane. It drew its name from Gallows Road, which was the forerunner of Baggot Street. Some 250 years ago, the Gallows River flowed through largely open countryside that became built up only in the 19th century, when the river disappeared from view.
The Liffey itself is a much cleaner river nowadays. Fortunately, the plans hatched in the late 1970s to build a barrage across the river were abandoned.
The subject attracts a certain kind of humour. The Creosote Stream, in its various branches, flows beneath the railway works in Inchicore and many decades ago the outdoor lavatories were placed directly above one of these watercourses. There was concern about the amount of time the men were spending there, studying racing form in the day's newspapers. A foreman had the bright idea of dousing balls of paper in oil and setting them alight before sending them downstream beneath the lavatories. It's said that the occupants emerged like greyhounds from the traps.