Irrigation Water Conveyance and Application Methods
Subtopic: Irrigation scheduling
Question Statement:
A tubewell operating 10 hours per day discharges water at a rate of 25 m³·h⁻¹. The average irrigation depth is 80 mm, and the irrigation interval is 20 days. If the intensity of irrigation is 80%, the culturable command area (in hectares) is ________. (Rounded off to two decimal places)
Official Answer Key:
7.50 to 8.00
Step-by-Step Solution & Explanation
Step 1 — total water pumped in one irrigation interval:
V = 25 m³·h⁻¹ × 10 h·day⁻¹ × 20 days = 5000 m³
Step 2 — area that this volume can irrigate at 80 mm depth:
A = V/depth = 5000/0.08 = 62,500 m² = 6.25 ha
Step 3 — convert irrigated area to culturable command area. An intensity of irrigation of 80% means only 80% of the CCA is under irrigated crop in that season:
CCA = irrigated area/intensity = 6.25/0.80 = 7.81 hectares
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