Irrigation Water Conveyance and Application Methods
Subtopic: Irrigation efficiencies
Question Statement:
A sandy loam soil has a water holding capacity of 140 mm m⁻¹ depth between field capacity and wilting point. The area to be irrigated is 60 ha and the depth of effective root zone is 0.30 m. The management allowed soil moisture depletion is 40% and the consumptive use is 6 mm per day. The conveyance and application efficiencies are estimated to be 80 and 50 percent respectively. There are no leaching requirements as well as no rainfall and groundwater contributions to the crop water requirement. The field irrigation requirement will be
Options:
(A) 21600 m³
(B) 10800 m³
(C) 2.16 × 10⁶ m³
(D) 27000 m³
Official Answer Key:
A
Step-by-Step Solution & Explanation
Using the rounded irrigation interval from Q76 (3 days), net depth actually to be replenished per irrigation = CU × interval = 6×3 = 18 mm. Field irrigation requirement (gross depth at the field, accounting for field application efficiency) = 18/0.50 = 36 mm = 0.036 m. Volume = 0.036 m × 60 ha × 10,000 m²/ha = 21,600 m³.
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