Due to the relative levels sometimes it is required to lower the bed of the irrigation channel of the drainage channel at their crossing.
When the bed of the irrigation channel is depressed and taken under stream it is called an irrigation siphon.
When the bed of the stream is depressed and taken under an irrigation channel it is called a drainage siphon.
The siphon crossing can be a rectangular closed masonry channel of circular brickwork of Rcc or pipe of the required diameter and number approach and exit may be through a masonry drop pit or of masonry slopped channel. The downstream end is kept lower than the upstream end by at least 15cm for better flow.