Comparison between canals and drains

Saturday, October 5, 2013 21:51
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Comparison between canals and drains

Following are the points of comparison between canal and drains.

Drain Canal
Nature Drain is naturally made. It is an artificial made structure.
Alignment Its alignment varies with the passage of time. Mostly it keeps its alignment.
Approach Meandering and braided in most cases. Canals are almost straight except on designed curves.
Bed slope Bed slope varies section to section and is normally 0.01% to 0.05%. Designed on a specific bed slope for a reach. Bed slope varies from 1/10,000 to 1/20,000.
Construction cost Normally no construction cost but training works involve a huge sum of money. High construction cost but low maintenance cost.
Discharge Higher discharge than that of canal. Lower than drain.
Free board No proper free boards so water over flowing from banks during floods. A certain free board is provided to keep the water within it. Usually free board > 2′.
Losses Mostly there are seepage and evaporational losses. Evaporational losses are low but there are seepage losses in unlined canals.
Side slopes No definite side slopes. Side slope is 1:1 to 2:1 in cutting and upto 3:1 in filling.
Supply of water Drains supply water to the barrages. Canals supply water to the branch canals and to distributories/minor canals.
Source of water Glaciers, springs, rains, catchment areas are the source of water to the drains. Canals get water from a barrage.
Level of water The level of water in the drain is called high flood level. The level of water in canal is called full supply level.
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