Cast iron siphons
Gravel barrier at Taumutu
Description of option
A series of cast iron syphons (approx 8 or 9 syphons) was proposed as an option to drain the lake.
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.
below 50 cumecs
Width of shingle bank (+ need for ends to be continuously submerged) requires long pipes - which need protection from waves & gravel.
"Pipes alone amount to double the price approximately of the land drained without allowing anything for timber foundations or casings" (Bray, 1875 in Harris, 1947).
Fish passage benefit rating
Potential running impacts or benefits