Each year thirty million tons of water is released from Poulaphouca Reservoir to bring the River Liffey up to flood level, thereby changing small rapids into raging torrents, weirs into foaming walls of water and flat stretches into swift currents and treacherous eddies. The event attracts over 1,000 canoeists from all over Europe to challenge the River Liffey as it clambers its way over ten weirs and numerous rapids, not to mention a long portage around Leixlip dam and a heavily wooded section – 28km in all making it a supreme test of canoeing skill, stamina courage and ability. The race began in 1960 as an inter-club event, but developed rapidly, becoming an international event by 1964 and it now attracts paddlers from many parts of the world.