Question

Water in a river 6m wide and 1.5m deep flows with a speed of 10km/hr. How much area will it irrigate in half an hour if 8cm of standing water is needed?

• A. 52.45 Hectares
• B. 49.25 Hectares
• C. 56.25 Hectares
• D. 66.76 Hectares

Answer 1

The correct option is C

56.25 Hectares

Volume of water coming out of 6m wide and 1.5m deep canal in 1 hour at a speed of 10,000m/hr
= 6 × 1.5 × 10,000 = 90,000$m^3$
Hence the volume of water coming out in half an hour is = 90,000 × 1/2 = 45,000 $m^3$
Let the irrigated area be x $m^2$
Standing height of water = 0.08 $\times$ x = 45000
x = 562500 $m^2$
1 Hectare = 10,000 $m^2$
So, x = $\frac{562500}{10000}$

= 56.25 hectare