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Siphons in dams and other water retaining structures (RP1131)

There are over 4000 regulated reservoirs in the UK (those over 25000/10000 cubic meters in size). Over the next 5 years, water companies will be  investing  in excess of £100m improving the management and operation of their reservoirs, including a substantial investment in the installation of siphons to improve draw down capability. A number of new reservoirs are also being constructed that will incorporate siphons. 

The ability to safely draw down a reservoir for maintenance or in emergency situations is vital.
Retrofitting bottom outlets through dams to increase draw down capacity is wrought with technical risk. In the UK the average dam height is around 7m which makes siphons feasible at many sites and for higher dams; the swift removal of water pressure exerted on the top 7 to 8m of the dam can significantly reduce risk.

This project will produce best practice guidance on the design, installation, operation, management and testing of siphons in dams.


This project is currently underway.
Research contract has been appointed to Mott MacDonald

Further information

If you are interested in this topic, please contact Jack Young at CIRIA.

Project proposal
(Adobe PDF File)