Irrigation Water Conveyance and Application Methods
Subtopic: Irrigation efficiencies
Question Statement:
A pump, discharging water at a rate of 80 L·s⁻¹, is used to irrigate 2 ha of land in 10 h. On irrigation, moisture content of the soil (on weight basis) in the root zone depth of 50 cm is increased from 18% to 30%. If bulk density of the soil is 1500 kg·m⁻³, water application efficiency in per cent is ______. [round off to 2 decimal places]
Official Answer Key:
62.25 to 62.75
Step-by-Step Solution & Explanation
Water applied = 80 L/s × 3600 s/h × 10 h = 2,880,000 L = 2880 m³. Root-zone soil volume = area×depth = 20,000 m² × 0.5 m = 10,000 m³. Dry-soil mass = 10,000×1500 = 1.5×10⁷ kg. Additional water stored (weight-basis) = dry-soil mass × Δw = 1.5×10⁷×(0.30−0.18) = 1.8×10⁶ kg = 1800 m³ (since 1 kg water ≈ 1 L). Water Application Efficiency = water stored in root zone / water applied = 1800/2880 = 62.5%.
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