Correct option is A
A cross drainage work is a structure constructed for carrying a canal across a natural drain or river intercepting the canal to dispose drainage water without mixing with the continuous canal supplies.
Types of Cross - Drainage Works:
(1) Type I (Irrigation canal passes over the drainage)
(a) Aqueduct
(b) Siphon aqueduct
(2) Type II (Drainage passes over the irrigation canal)
(a) Super passage
(b) Siphon super passage
(3) Type III (Cross drainage works admitting the drain water into the canal)-
In this type of cross drainage works, the canal water and the drain water are allowed to intermingle with each other.
This may be achieved by the following two types of cross drainage works:-
(a) Level crossing
(b) Inlet and outlet
Aqueduct:
The highest flood level of the drainage remains lower than the level of the underside of the canal trough.
The drain water flow under the canal such that there is sufficient headway available between the HFL of the drain and the underside of the canal trough.
The drain water flows at atmospheric pressure.
An inspection road is provided along the side of the trough.
Siphon Aqueduct:
In the siphon aqueduct, the bed of the drainage is depressed below the bottom level of the canal trough by providing a sloping apron on both sides of the crossing.
It is constructed where the water surface level of the drain at high flood is higher than the canal bed.
The drain water flows under pressure.
Super Passage:
The super passage is just opposite the aqueduct.
In this case, the bed level of the drainage is above the full supply level of the canal.
The canal flows at atmospheric pressure.
Siphon Super Passage:
It is just the opposite of siphon aqueduct with the difference that in this case, the canal water is carried through the barrels under the drain.
The barrels in this case also act as inverted siphons through which the water flows under pressure.
The bed of the canal is depressed below the bottom level of the drainage trough by providing a sloping apron on both sides of the crossing.
