Dublin drinking water supplies on knife-edge as it over-relies on vulnerable Liffey

The Liffey is like a big ‘U’ sitting on its right side. From its source in the Wicklow Mountains, it turns towards the plains of Co Kildare and from Leixlip goes through the most densely populated part of Ireland where environmental threats multiply until it reaches Dublin Bay.

The river supplies 85 per cent of drinking water for the greater Dublin area, with a population exceeding 1.7 million. Some 500 million litres is extracted daily from the river at Ballymore Eustace and Leixlip.

If a major pollution incident occurs it is in trouble. Few capital cities of similar size would be so reliant on a single source of drinking water. Risks were laid bare when the Leixlip water treatment plant broke down in 2019. It prompted a boil water alert affecting 615,000 people.

The problem was fixed by Uisce Éireann, the State’s water utility but, arguably, it is a sticking plaster solution. Up to 68 per cent of water supplies in the region are at risk of failure during drought conditions. It has the lowest rainfall in the country.

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The Liffey is a relatively small waterbody for such large extraction of water with a catchment of just 1,000 square kilometres, according to Uisce Éireann’s assets strategy manager Angela Ryan. Dams enable extraction and storage further upstream on the Liffey at the Poulaphouca reservoir next to Blessington in Co Wicklow, but it has just three months’ worth of supply.

Extreme weather events can affect both water availability and quality. Heavy rainfall combines with run-off from roads and pavements washing into the system, creating dirtier water. With low volumes, there is less water to dilute pollutants.

All told, it is “a very vulnerable situation”, says Ryan. The main treatment facilities in Ballymore Eustace and Leixlip are designed to remove associated pollutants but are constantly running at near 100 per cent capacity.

Ryan describes 2019 as “a perfect storm” due to high demand with the plant running with no spare capacity, while they were attempting to upgrade water filters. A spike in turbidity (cloudiness) indicated filters were struggling and prompted the boil water notice.

Typically in Paris and Lisbon there would be 40 per cent redundancy in plants with the ability to switch to other sources if needed. “There is no redundancy in Irish treatment plants,” says Ryan.

Leixlip has an improved alarm system, new filters and ultraviolet light treatment but “it will never be a resilient system because of lack of redundancy”, she adds.

Compounding matters is the population growth of Kildare and Meath, the suburban counties around Dublin. While Uisce Éireann is deploying a leakage reduction programme to reduce demand, “you will never achieve resilience without a new source”, she says.

In short, the problem is “a small catchment and a giant population”. In response, Uisce Éireann is proposing to extract water from another river, the Shannon, and pipe it to the greater Dublin area. It has a catchment of 14,000sq km and two years’ worth of storage in Lough Derg. About 100 million litres per day will be needed as the Liffey will still be used.

The problems, however, are so precarious. Some 50 projects costing €100 million are addressing supply constraints including network connectivity problems while improving reservoir storage. EPA monitoring shows Liffey water bodies vary from high ecological status in its upper-most stretches to poor as it enters the sea.

By 2044, Uisce Éireann forecasts it will need 34 per cent more water in the eastern and midlands region than today. The plans are based on 20 per cent population growth, yet the Central Statistics Office is predicting 40 per cent by 2036, says Gretta McCarron of An Fóram Uisce, a statutory body that advises the Government.

[ The Liffey is filthy, but can you imagine if it was clean enough to swim in? ]

[ Niall Gleeson of Uisce Éireann: ‘If anything happened to the river Liffey, we would be in trouble’ ]

This is “a notable weakness in their plans” given the likely increases in industrial and data centre demand.

It has detailed how climate impacts, notably droughts and intense rainfall, affect availability and quality of water sources. The greater Dublin area is especially vulnerable, McCarron confirms, with “a supply demand deficit” which worsens during drought. There is no drought management plan for the Liffey.

Sustainable Water Network co-ordinator Sinead O’Brien says the Liffey is “healthy” as far as Celbridge, while from Lucan in west Dublin on into the city centre, the water quality deteriorates. Agricultural impacts are worsening though waterbodies impacted by sewage have decreased significantly.

Nutrients (animal and human wastes) are the biggest threat, she says; the latter is from combined sewer overflows that overload and discharge into the Liffey.

The problem is worsened by misconnections, industrial pollution, run-off from roads and poorly performing storm drains which act as emergency safety valves releasing excess flow.

Swimmers, kayakers and rowers on the river are well used to health risk, she says.

The fact that it supplies the water for the city and yet has been allowed to degrade to such a point is atrocious

—  Pádraic Fogarty - Ecologist

“There is a lot of cases of unreported illness. I don’t think we should accept that as a reality. Dublin should be like Copenhagen and Paris which plan to make their cities ‘swimmable’,” says O’Brien.

The EPA agrees excess nutrients such as nitrogen and phosphorus, leading to eutrophication are the main problem: “The sources of nutrients include agriculture and domestic wastewater in the northern parts of the catchment around Maynooth and Dunboyne, and urban runoff and wastewater discharges in the more densely populated areas in Dublin city.”

“One of the tragedies is the uplands – where the water comes from – is destroyed,” says ecologist Pádraic Fogarty. It has been burned, overgrazed by sheep and covered in conifer plantations. “The fact that it supplies the water for the city and yet has been allowed to degrade to such a point is atrocious.”

Conversely, he adds, restoring the uplands would be an amazing thing to do, “because it would hit so many boxes. It would improve the water quality; it would help to mitigate the flooding and regulate water flow. It would improve the biodiversity... and be a fantastic amenity.”

He supports the idea of having a nature reserve in Liffey Valley, one of the city’s biggest open spaces but “virtually impenetrable from a public/walkers’ point of view”. Looking on Google maps, he says there is a lot of golf courses and private demesnes, but also a substantial green corridor as far as Islandbridge.

On biodiversity, there are a lot of barriers and weirs including a hydroelectric power station and drinking water reservoir upstream of Lucan making it almost impossible for migratory fish to negotiate most of the Liffey. Pressure is obvious through Co Kildare because of intensive farming while raised bogs around Newbridge, that feed into the river, are “severely damaged”, he adds.

From there on it improves a little, he concedes, but large areas have no trees, when there should be a “wood corridor” through Liffey Valley, set 50 to 100 metres with native trees on either side of the river which would give it space and enhance its “ecosystem services”.

The Liffey’s biodiversity status has declined over many years, Fogarty says, since the 1800s when oysters and many varieties of fish were found in Dublin Bay, and salmon, eel and sturgeon were common in the Liffey. It’s not all bad news, as otters and kingfishers are plentiful, which for a capital city is notable, while there is a decent amount of semi-natural woodland on Dublin side of the Liffey Valley.

One of the easy wins, Fogarty believes, is removing barriers, ie restoring fish migration routes, opening it up to salmon, eels, lamprey and even turbot. The big opportunity is to reforest uplands and protect blanket bogs, while restoring oyster beds and fish life in Dublin Bay, though that would depend on improving water quality.

He favours reintroducing sturgeon and following London in introducing beavers to help restore nature and reconnect people with the river. Dublin should follow Singapore, he suggests, in rewilding its urbanscape by enhancing biodiversity; ponds, trees and wetlands, which will make it more climate resilient and a nicer place to live in.

Tomorrow: Mark Hilliard looks at how Intel, one of the countries largest multinational employers, draws water from the Liffey for chipmaking.