Siphon

Year proposed

  1970

Status

 Not implemented

Location description

  It could be placed at various locations along the spit between the lake and the sea.

Description of option

  The siphon was proposed as an option which would be continuously running with minimal energy inputs. However, it would require priming to start, gases could condense and accumulate at the crest, there could be a cavitation potential, and the behaviour of the siphon is unknown in the surf zone.

Opening, closing, and lake level control description

  Continuous low flows and good opening & closing control but less than ideal lake level control (unless many used). Ends of pipes must always be submerged to operate.

Maximum discharge

  below 50 cumecs

Maintenance/Management description

  The Siphon needs to be checked regularly for correct functioning.

Cost description

  A pump for priming would be required.  Cleaning and general maintenace (cleaning, fixing) is required.

Fish passage benefit rating

  Low

Potential running impacts or benefits

  The effect of the swells and tides on the behaviour of the siphon are largely unknown. In a heavy swell, a dramatic reduction in available head could stop the flow through the siphon. For low lake levels the hydraulic gradient may also be insufficient.