Irish Water’s plan to take Shannon water to meet needs of greater Dublin area is complex

Irish Water’s plan to extract water from the lower reaches of the Shannon to meet the needs of the greater Dublin area is not a straightforward matter of pipes and pumps, according to Pat Aherne.

And he knows more than most about the complex issues which face the proposed €900m project. For years he worked with the technical staff at Ardnacrusha ESB power station which impacts hugely on the lower Shannon system. And as a keen angler he knows every nook and cranny of that stretch of the river.

Pointing to an aerial photograph in the sitting room of his bungalow, Mr Aherne shows that his home just outside O’Briensbridge, Co Clare, is only a few hundred metres from the man-made lake at the weir of the Parteen Basin, the source of the proposed new Dublin supply. Parteen Basin is actually more than 13km up river from the village of Parteen near the Ardnacrusha station.

When the station was built more than 85 years ago, a ready supply of fast-flowing water was needed to drive its huge turbines. To achieve this, the Parteen Basin was created by flooding a large area of land along the Shannon and this was connected by a channel leading to the power station. This 13km channel, called the head race, runs parallel to the Shannon.

Mr Aherne said: “At the end of Lough Derg, the river resumes above Killaloe at Two Mile Gate, and comes through Killaloe and widens again at Parteen Weir and that’s what they call Parteen Basin. When the basin was created the level of water rose by about 14ft, submerging a large area. Parteen Basin is about a mile and a half in length.”

Three gates of Parteen Weir leading to the Ardnacrucha station are open all the times, and a fourth gate of the weir leading to the Shannon is controlled by the ESB to maintain specific river levels. The task of maintaining the river level between Parteen Weir and Limerick is the sole responsibility of the ESB.

“This is an area that will need to be addressed. Who will be responsible for ensuring that the level of the Shannon between Parteen Weir and Limerick is maintained at proper level?” asked Mr Aherne.

He is also concerned with what will happen upstream from the Parteen Basin.

He said: “There is a lot of variation in water levels in the Parteen Basin. These are controlled by the ESB during periods of heavy rain, by allowing ‘spills’ from the basin through the weir gate into the Shannon and opening up the turbines at Ardnacrusha.

“If the basin is to become a new source for the east of the country, what input will the ESB have in controlling the levels of the basin? Who will be in charge of ensuring levels are properly maintained?”

Mr Aherne said that he was surprised that Irish Water has chosen Parteen Basin as its preferred supply source.

“I gathered that it would be further up the Shannon at a location closer to the east of the country,” he said.