Canals:
Canals are artificial
waterways constructed for various purposes including irrigation, navigation, water
supply, or drainage.
Classification
According to Alignment and Position in the Canal Network:
- On the basis of alignment, canals can be divided into:
- Watershed or Ridge Canals: These are aligned along the watershed
line between two drainage areas. The main advantage is the minimum area
is submerged but the cost of construction is generally high due to the
need for many cross-drainage works.
- Side-Slope Canals: These canals are aligned along the side
slope of a valley. They need less earthwork but the area of submergence
is generally more than ridge canals.
- Contour Canals: These are aligned nearly along a contour
line. They are used where it is necessary to command a higher-level tract
of land.
- On the basis of the position in the canal
network, canals can be
divided into:
- Main Canal: This is the primary canal that
originates from the river and carries water to the major part of the
irrigated area.
- Branch Canals: These canals branch off from the main
canal to serve different areas.
- Distributaries or Field Channels: These are smaller canals that originate
from the main or branch canals and distribute water directly to the
fields.
Cross Section of
Canal in Embankment and Cutting:
- A canal in embankment (above ground
level) usually has a trapezoidal cross-section, with the wider part at the
top. This helps provide stability and prevent the canal from collapsing
due to the pressure of the water.
- A canal in cutting (below ground
level) may also have a trapezoidal cross-section, but it can be narrower
than a canal in embankment because the surrounding ground provides
additional support.
- Partial embankment and cutting refers to a canal that is partly above
and partly below the natural ground level. The cross-section in this case
would depend on the specific circumstances, but it could have features of
both embankment and cutting sections.
Balancing Depth:
Balancing depth refers
to the depth of water in the canal that gives the most economical flow - that
is, the flow with the least energy loss due to friction. It is typically
calculated as part of the design process based on factors such as the flow
rate, the slope of the canal, and the characteristics of the canal material.
Design of Most
Economical Canal Section:
Designing the most
economical canal section involves finding the dimensions that will provide the
required flow capacity at the minimum cost. This usually means minimizing the
amount of excavation or embankment required, while still ensuring the stability
of the canal and the efficient conveyance of water. The specific design will
depend on many factors, including the flow rate, the slope of the ground, the
characteristics of the soil, and the cost of construction.