Irish waterways: the toll of years of draining, modification and engineering

The word in Irish is “sruthán”: a small slip of a stream, a rivulet. It might begin life in a sodden bog or meadow, then trickle downwards through fields and under bridges – a watery capillary winding across the landscape – before joining forces with another stream.

One morning last week, I stood with Pat Lee, a suckler and sheep farmer in Mayo, a few metres from his sruthán, the Ower and watched it flow into the larger, shimmering Black river, An Abhainn Dubh, in the corner of one of his fields.

While the Ower emerges from a wet field about a mile north of Pat’s farm, the start of the Black river is a turlough about eight kilometres to the east in Kilmaine. It then flows over limestone rock through Shrule, following the Mayo/Galway border, and alongside Pat’s organic farm east of Headford. Two miles downstream, it empties into the eastern shores of Lough Corrib. The life that depends on the Corrib – the eels, salmon, trout, lamprey and hundreds of invertebrates – also relies on these tributaries as nursery grounds and places to feed and live.

During winter and spring, when the rain is heavy, water will frequently spill over at the confluence of the Ower and Black river on Pat’s land. It’s a reminder that this slice of the field is part of them. Waterways expand and contract with the seasons, occupying a dynamic space beyond their summer banks.

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Like nearly all of our waterways of the past century or so, the Black river has been drained, modified and engineered. It’s the story of the evolution of farming. Historically, Ireland was not a land of green pastures; it was soggy and wet. To produce food, field drains were laid to dry the land out. If the field is sloped, the excess water flows with gravity to the nearest stream or river. But where land is flat – which is the case in the midlands – rivers and streams were deepened to create an artificial gradient.

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Instead of piecemeal drainage works carried out by individual landowners, the State introduced the Arterial Drainage Act in 1945, which transferred responsibility to the Office of Public Works, which took a catchment-level approach. Because rivers and streams retain a kind of water memory and will constantly try to revert to their original form, the OPW became legally responsible for keeping the modified channels clear.

And so, thousands of acres of land were brought into food production. Today, drainage works on 11,500km of river channels and 800km of embankments provide discharge for 260,000 hectares of agricultural land. But the Act set the Irish State on an expensive and unwinnable war against water and nature, causing untold damage to habitats for fish, wetland birds, and species such as the freshwater pearl mussel and the natterjack toad. It has proven disastrous for flooding, too; using rivers merely as drains for water, which would otherwise be slowly soaked up and released by the land, is a recipe for flash flooding in towns and villages downstream.

The work needed to keep the channels clear involves using hydraulic excavators, mini-diggers, tractors and trailers, tipper lorries, weed-cutting boats, chainsaws, mulchers, mowers and shears. Silt and vegetation are scooped out of river channels and spread along the bank or onto spoil heaps. Herbicides are sprayed, and scrub and woodland on the banks are trimmed away.

If the 1945 Act is consigned to the history books, is there a cheaper, more effective alternative?

Historically, the low-lying Stonyford river in Meath, a tributary of the Boyne, meandered through wetlands and would flood its banks in winter, depositing finer silt and clay onto the land. In the 1960s, the land was drained for farming. The surplus water from the fields had nowhere to go, so the OPW lowered the water table by deepening the river through dredging and rock blasting along the river bed.

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The drainage worked for agriculture but left an artificially deep river clogged up with silt. And so, the OPW would send in the diggers to clear the silt and vegetation, causing the water to rapidly drain downstream. This maintenance cycle – expensive, destructive, but effective in the short term – continued for decades.

Then, in the winter of 2014, the OPW dredged the river for the final time. They fenced the waterways to keep the livestock from accessing the water and eating the vegetation along the banks. Over six years, how would the river respond to this experiment in passive restoration? Scientists from Inland Fisheries Ireland waited and watched to see what nature would do.

Given extra time without being dredged, the silt in the river – a fertile mix of clay, sand, dead bits of plants and fish, wood and leaves – moved towards the edges where vegetation secured it. The amount of silt in the riverbed halved. The centre of the river became covered in gravel, which is the ideal habitat for invertebrates and spawning fish. Overall, this low-cost experiment in allowing the river to renaturalise itself has improved the physical characteristics of the river to benefit the species who live in it.

There are nearly 2,500 people employed by the OPW, yet just three are ecologists, and one is an environmental scientist. If we want any chance of restoring our waterways and minimising flood risk, we need the expertise and ambition to understand, respect and implement nature-based solutions to help solve our extensive problems. Standing with nature, not against it, is our best chance.