Main Difference
The main difference between Drainage and Canal is that the Drainage is a natural or artificial removal of surface and sub-surface water from an area and Canal is a man-made channel for water.
Drainage
Drainage is the natural or artificial removal of a surface’s water and sub-surface water from an area with excess of water. The internal drainage of most agricultural soils is good enough to prevent severe waterlogging (anaerobic conditions that harm root growth), but many soils need artificial drainage to improve production or to manage water supplies.
Canal
Canals, or navigations, are human-made channels, or artificial waterways, for water conveyance, or to service water transport vehicles.
In most cases, the engineered works will have a series of dams and locks that create reservoirs of low speed current flow. These reservoirs are referred to as slack water levels, often just called levels.
A canal is also known as a navigation when it parallels a river and shares part of its waters and drainage basin, and leverages its resources by building dams and locks to increase and lengthen its stretches of slack water levels while staying in its valley.
In contrast, a canal cuts across a drainage divide atop a ridge, generally requiring an external water source above the highest elevation.
Many canals have been built at elevations towering over valleys and other water ways crossing far below.
Canals with sources of water at a higher level can deliver water to a destination such as a city where water is needed. The Roman Empire’s aqueducts were such water supply canals.
Drainage (noun)
A natural or artificial removal of surface and sub-surface water from a given area.
Drainage (noun)
A system of drains.
Canal (noun)
An artificial waterway or artificially improved river used for travel, shipping, or irrigation.
Canal (noun)
A tubular channel within the body.
Canal (noun)
One of the faint, hazy markings resembling straight lines on early telescopic images of the surface of Mars.
Canal (verb)
To dig an artificial waterway in or to (a place), especially for drainage
Canal (verb)
To travel along a canal by boat
Canal (noun)
an artificial waterway constructed to allow the passage of boats or ships inland or to convey water for irrigation
“the Oxford Canal”
“they travelled on by canal”
Canal (noun)
a tubular duct in a plant or animal, serving to convey or contain food, liquid, or air
“the ear canal”
Canal (noun)
any of a number of linear markings formerly reported as seen by telescope on the planet Mars.