Representatives of Department of Infrastructure (DfI) Rivers and RPS Consulting Engineers recently visited Ulster Farmers’ Union (UFU) Headquarters to give UFU representatives an update on the findings of the review of the Lough Neagh Operating Scheme.
The Lough Neagh catchment area drains 43% of Northern Ireland’s land mass (Source: DfI Rivers) and during periods of heavy or prolonged rain the increased flow of water from the six main rivers that flow, into Lough Neagh, can result in a rise in the Lough’s water level. This can lead to flooding of low-lying areas and render land temporarily unusable. Therefore, UFU and DfI Rivers, who have responsibility to regulate the water levels on Lough Neagh, continue to engage meaningfully.
DfI Rivers is required to regulate and control water levels in Lough Neagh within a statutory range of (12.45m to 12.6m OD), in so far as climatic conditions allow. Water levels in the Lough, which can be viewed online, are controlled by means of floodgates at Toome the head of the Lower Bann River with further controls in place along the Lower Bann River with two sets of floodgates located at Portna (near Kilrea), and the Cutts at Coleraine. Each morning, readings are taken from four gauging stations, and used to determine the water level around the lough. Weather forecasts and the previous three days’ conditions are checked and based on the time of the year and previous experience, a decision is then taken on the need to make any required adjustments to the sluice gates at Toome.
The Strong Report on the winter flooding in 2015/16 included a recommendation to review the Lough Neagh and Lower Bann operating scheme. As part of this work, a hydrodynamic model of the Lough and Lower Bann was constructed by RPS and a range of alternative operating schemes were identified and simulated for the 2015/16 event to determine whether another regime would have significantly reduced the flood levels observed over this period. The review concluded that any alternative operation of sluice gates, outside that carried out by DfI Rivers, would have an insignificant effect on the levels that occurred during the winter of 2015/16.
The review also confirmed that the channel in the Lower Bann River, downstream of Lough Neagh, tends to impede the rate of outflow from the Lough during periods of heavy rainfall. Therefore, in order to significantly reduce the peak water level during significant flooding events the restrictions along the Lower Bann would have to be removed. This work would however be prohibitively expensive with associated negative environmental impacts and is not considered to be a viable option. Nevertheless, in order to improve the response to any future flooding DfI Rivers are undertaking further work to try to better understand when the Lough will peak during prolonged flooding periods. This should allow for additional guidance to be provided for farmers with land on the Lough shores at times of concern.