This standard provides criteria for the hydraulic and structural design of canal siphons, used to carry canal water under obstructions like natural drains. It covers aspects such as determining the required size of the siphon barrel, calculating head losses, and designing ancillary components like transitions and protection works. The code aims to ensure safe and efficient passage of water with minimal afflux and erosion.
Lays down criteria for the hydraulic and structural design of siphons for irrigation and other water conveyance systems.
Quick Reference Values
Recommended velocity in siphon barrel2.0 to 3.0 m/s
Maximum permissible afflux0.3 m
Entry loss coefficient (ke) for square edged entry0.5
Exit loss coefficient (kx) for abrupt exit1.0
Minimum freeboard for drain upstream of crossing0.75 m
Key Formulas
Total Head Loss (HL) = Entry Loss + Friction Loss + Exit Loss + Bend Loss
Friction Loss (hf) = (n^2 * V^2 * L) / R^(4/3)
Transition Loss = k * (V^2/2g)
Practical Notes
Ensure design velocity is sufficient (typically > 2 m/s) to prevent silt deposition within the siphon barrel, a common operational problem.
Pay close attention to the design of trash racks and stop-log grooves as they are critical for maintenance and preventing blockages.
Inaccurate estimation of head loss coefficients for transitions (inlet/outlet) is a common source of design error; use bell-mouthed entries where possible to reduce entry losses.