Question

An irrigation canal is 80 km long. It has an average surface width of 15 m. If the evaporation measured in a Class A pan is 5 mm/day, the volume of water evaporated in a month of 30 days is: (take pan coefficient as 0.7)

• A. $18000{\text{m}}^3$
• B. $126000{\text{m}}^3$
• C. $18000{\text{cm}}^3$
• D. $126000{\text{cm}}^3$

Answer 1

The correct option is B $126000{\text{m}}^3$

$\text{Evaporation from class A pan}=5\text{mm / day}$
$\text{Lake evaporation}=C_p\times \text{pan evaporation}$
$=0.7\times 5\text{mm/day}$

Total evaporation in 30 days
$=0.7\times 5\times {10}^{-3}\times 80\times {10}^3\times 15\times 30$
$=126000m^3$