Superpassage is a type of canal cross-drainage structure that allows the passage of natural stream water below a canal. It is designed to ensure the smooth flow of both canal water and natural stream water without any obstruction or disruption. Let's understand the concept in detail.

- Nature of Superpassage:
A superpassage is a hydraulic structure that is constructed at a canal crossing over a natural stream. It is designed to accommodate the flow of natural stream water underneath the canal, ensuring a free surface flow. The purpose of a superpassage is to prevent any interference between the natural stream and the canal system.

- Flow of Water:
In a superpassage, the natural stream water flows with a free surface below the canal. This means that there is no pressure exerted on the natural stream water by the canal. The water in the stream flows naturally, following its own hydraulic gradient, without any artificial pressure.

- Design Considerations:
When designing a superpassage, various factors are taken into consideration to ensure its effectiveness and functionality. These factors include the water levels, velocities, and discharges of both the canal and the natural stream. The dimensions of the superpassage are determined based on these factors to ensure adequate passage capacity.

- Structure Components:
A typical superpassage consists of several components that work together to facilitate the flow of water. These components include:

1. Head Regulator: It is provided at the upstream end of the superpassage to control the flow entering the superpassage.

2. Superpassage Bed: The bed of the superpassage is constructed below the canal bed and allows the natural stream water to flow freely.

3. Side Walls: Side walls are constructed along the superpassage bed to contain the flow of water and prevent any erosion.

4. Wing Walls: Wing walls are provided at both the upstream and downstream ends of the superpassage to guide the flow of water and prevent any disturbances.

5. Exit Structure: At the downstream end of the superpassage, an exit structure is constructed to smoothly discharge the water back into the natural stream.

- Advantages:
Superpassages have several advantages, including:

1. They allow the natural stream water to flow freely without any obstruction, maintaining the ecological balance.

2. They prevent any interference between the canal water and the natural stream water, ensuring the efficient functioning of both.

3. They minimize the risk of flooding by providing a controlled passage for the natural stream water.

Overall, a superpassage is a critical structure in canal crossings over natural streams. It ensures the smooth flow of water and prevents any disruptions or interference, maintaining the efficiency and functionality of the canal system and the ecological balance of the natural stream.