The ESB has confirmed to the Tipperary Star that it lowered water levels in Lough Derg in May for maintenance works. The confirmation comes following concerns by anglers and boat owners, as well as the River Shannon Protection Alliance, that the lake was lowered to study water levels if Irish Water goes ahead with its plan to take water from Lough Derg and pipe it to Dublin.
Ervia, the company with responsibility for Irish Water, had told the Tipperay Star that the lake was lowered by the ESB but had directed enquiries on the nature of the work to the ESB.
In a statement, the ESB said it lowered water levels in late May at a time when essential maintenance works were being undertaken on infrastructure on the Lower Shannon and high rainfall was forecast. The level to which the lake was lowered was within the normal operating range. These maintenance works are now complete and the level in Lough Derg has subsequently risen.
The ESB carried out maintenance to the bearings and joints of O’Brien’s Bridge, Clonlara Bridge, Blackwater Bridge and Parteen Bridge. This work involved a cherry picker working off a pontoon. In order to allow this work to be carried out safely, flows through the headrace had to be limited. Separately, a scheduled outage to a turbine in Ardnacrusha took place, meaning that Ardnacrusha’s capacity for passing flows was temporarily curtailed.
The Black River Culvert, which enters the Shannon below Parteen Weir, was also cleaned. This takes place every 10 years in order to allow an inspection be carried out. In order to safely carry out work in the culvert, the water level in Lough Derg had to be such that there was a low risk of spilling at Parteen Weir.
The occurrence of these three maintenance events together meant that ESB’s normal capacity for dealing with flows on the Shannon was curtailed. In order to account for this and to allow the work to be carried out safely, the level in Lough Derg was lowered to make as much storage available as possible. The level to which the lake was lowered was within the range of levels to which Lough Derg is regulated.
In addition, during periods of very low flow - as was the case last year - ESB aims to have a high water level in the lake to ensure that if there were a severe and prolonged drought, the lake level would not be reduced to too low a level.