An aqueduct is a structure carries canal water through it and crosses over a natural drainage river or nallah. An aqueduct is provided when canal bed level is higher than HFL of natural drainage.
In case of open through aqueduct the service road is discontinuous, and during rainy season for inspection of aqueduct site engineer has pass through submersible causeway to downstream side aqueduct. In this case cost of aqueduct and cost of the causeway and service road is to be borne by irrigation department. But during heavy flood the water flow over cause way and it can not be possible to inspect aqueduct for throughout length. Hence closed box aqueduct is proposed in place of existing open trough aqueduct.