water in a canal 30 dm wide and 12 dm deep, is flowing witha velocity of 20km/h, how much area will it irrigate in 30 minutes if 9cm of standing water is desired?
1 dm = 10 cm
Width of canal = 30 dm = 300 cm Depth of canal = 12 dm = 120 cm
Flow rate of water = 20 km/hr
Distance covered by the water that will flow in 30 minutes = (20 × 30 ÷ 60) km = 10 km = 10, 00,000 cm
Amount of water irrigated in 30 minutes
= 300 × 120 × 10,00,000 cu cm
Area irrigated by this water if 9 cm standing water is desired = (300 × 120 × 10,00,000 ÷ 9) sq cm = 4,00,00,00,000 sq cm = 4,00,000 sq m = 0.4 sq km.