In an aqueduct, natural drainage is ________________ the canal.
below
Understanding Aqueducts and Natural Drainage
An aqueduct is a structure designed to transport water, typically for irrigation or consumption, across geographical obstacles like valleys, rivers, or natural drainage paths. When a canal carrying water encounters a natural stream or drain, a crossing structure is required to allow both the canal water and the natural flow to proceed without interference.
Aqueduct Structure and Canal Crossing
One common method for a canal to cross a natural drainage channel is by using an aqueduct. In this type of crossing, the canal is carried in a trough or flume, which is supported by piers or an embankment structure. This elevated structure allows the natural drainage to flow underneath it.
Consider the purpose: the canal water needs to maintain its level and flow path, while the natural drainage, which is often at a lower elevation in the landscape, must continue its natural course. By elevating the canal using an aqueduct, the natural drainage path remains unobstructed.
- The canal is built at a higher level, often in a channel or trough made of concrete or masonry.
- Support structures like columns or walls are used to lift this canal trough above the ground level.
- The natural drainage channel flows freely in its original path, but now passes beneath the elevated canal structure.
Therefore, in the case of an aqueduct, the natural drainage channel is positioned below the level of the canal that is being transported over it.
Comparison with Other Crossing Structures
While an aqueduct is specifically designed for the natural drainage to be below the canal, other types of crossing structures exist:
- Super Passage: Here, the natural drainage is carried above the canal. This is less common for large natural drains crossing canals.
- Level Crossing: Both the canal and the drainage are at approximately the same level and cross each other at the same elevation, usually requiring regulatory measures to manage flow and prevent mixing.
- Siphon: The canal or drainage is carried below the other channel by passing through a closed conduit under pressure. In an inverted siphon (or canal siphon), the canal dips below the obstruction (like a drainage) and rises again. If a drainage is carried below the canal, it might be called a drainage siphon.
However, the question specifically asks about an "aqueduct," where the defined configuration involves the canal being elevated to cross over the natural drainage.
Conclusion on Drainage Position in an Aqueduct
Based on the definition and typical construction of an aqueduct, the natural drainage flows underneath the canal. This means the natural drainage is situated below the canal.
Thus, in an aqueduct, natural drainage is below the canal.
Revision Table: Canal Crossing Structures
| Structure Type | Position of Canal relative to Drainage | Position of Drainage relative to Canal |
|---|---|---|
| Aqueduct | Above | Below |
| Super Passage | Below | Above |
| Level Crossing | At the same level | At the same level |
| Siphon (Canal Siphon) | Dips below, then rises | Above (but canal passes underneath via pipe) |
| Siphon (Drainage Siphon) | Above | Dips below, then rises (drainage passes underneath via pipe) |
Additional Information: Importance of Canal Crossing Design
Designing canal crossing structures like aqueducts is crucial in irrigation and water supply projects. Proper design ensures:
- Continuous and efficient water flow in the canal without interruption.
- Unimpeded flow of natural drainage, preventing flooding upstream.
- Structural stability and safety of both the canal structure and the crossing structure.
- Prevention of mixing between canal water (which might be treated) and natural drainage water.
- Minimization of maintenance requirements.
The choice of crossing structure depends on various factors including the relative levels of the canal and drainage, discharge amounts, geological conditions, and economic considerations. An aqueduct is chosen when the canal needs to pass above the natural drainage effectively and efficiently.
Important Questions from Cross Drainage Works
When the HFL of the drain is sufficiently below the bottom of the canal, so that the drainage water flows freely under gravity, the structure is known as _______
The velocity of drainage water in the barrels of syphon aqueduct is normally limited to
- A cross drainage structure in which the drain is taken over a canal, the canal water runs freely under gravity is -
______ is a passage for water over a natural ground having a deck slab over it as path way for vehicles.
The distance between bottom of the bridge super structure and H.F.L is known as____.
