Operational experience with existing siphons

SSE operates four reservoirs that had siphons installed in the dams during the original construction. These siphons are provided to increase flood discharge capacity, reducing the flood rise at each of the dams, without significantly increasing the spillweir length. A brief description of each siphon system is provided, including how the siphons operate. Operational issues that have arisen in the past and how these have been dealt with are discussed. These include issues arising from the originally designed layout, issues arising during operations such as vegetation blocking screens or air intakes, personnel safety requirements, and deterioration of key elements of the siphons. Improvements have been made at some of the siphons arising from these issues and these are described. The learning from all of these issues has resulted in a refreshed inspection, testing, and maintenance regime being implemented over the last few years to ensure effective operation of the siphons in a flood event.