Question

Water in a canal 30 dm wide and 12 dm deep, is flowing with a velocity of 100 km per hour. How much area will it irrigate in 30 minutes if 8 cm of standing water is desired?

Answer 1

$\text{Width of canal (b)}=30dm=3m$

$\text{Depth (h)}=12dm=1.2m$

$\text{Speed of water}=100km/hr$

$\text{Length of water flow in 30 minutes}=\frac{1}{2}hr$

$=\frac{100\times 1000}{2}=50000m$

$\therefore \text{Volume of water}=lbh=3\times 1.2\times 50000m^3$

$\text{Depth of water in the field}=\frac{8}{100}m$

$\therefore \text{Area of field}=\frac{\text{Volume of water}}{\text{Depth of water}}$

$=\frac{3\times 1.2\times 50000}{\frac{8}{100}}$

$=\frac{3\times 12\times 50000\times 100}{10\times 8}=9\times 250000$

$=2250000m^2$

It will irrigate $2250000m^2$ in 30 minutes if 8 cm of standing water is desired