The recommended range of the velocity of the drainage water in the siphon barrels in m/sec is:

Explanation:

Siphon Aqueduct;

• A syphon aqueduct is constructed where the water surface level of the drain at high flood is higher than the canal bed.
• The horizontal floor of the barrels is provided with slopes at its ends to join the drain bed on either side.
• The drain water flows under pressure through the barrels which act as inverted syphons hence this cross-drainage work is known as a syphon aqueduct.
• The velocity of drainage water in the barrels of syphon aqueduct is normally limited to 2 to 3 m/sec.

​Hence option (2) is the correct answer.