The Shimna River.

The Shimna River rises on the northern slopes of Slieve Melbeg in the Mourne Mountains, County Down. Fofanny Dam was built in the 1960's to supply water to the Banbridge, Portadown and Newry areas. The original treatment plant designed to treat 32 million litres of water a day was replaced at a cost of £18m, the new plant is almost totally underground minimising the visual impact on the .environment.

The water from a smaller river flowing in the valley between Slieve Melmore and Melbeg, has been captured and transported via a pipeline around the lower slopes of Melbeg to Fofanny Dam.