Question

Water in a canal, 30 dm wide and 12 dm deep, is flowing with a velocity of 20 km per hour.How much area will it irrigate, if 9 cm of standing water is desired?

Answer 1

Depth = 12dm = 1.2m
width = 30dm = 3m
flow velocity = 20km/h = 20,000 m/h
time = 30minute = 0.5 hour
standing water required = 9cm = 0.09m
Let the area = A $m^2$

Volume of water will be same
1.2m x 3m x 20,000 m/h x 0.5 h = A x 0.09
⇒ A = 36000/0.09
⇒ A = 4,00,000$m^2$ = 40 hectare

40 hectare plot can be irrigated