Section 4: Soil and Water Conservation Engineering
Soil Mechanics
Subtopic: Engineering properties of soils
Question Statement:
An irrigator estimates the depth of infiltration (mm) around a field on a 5×4 grid: 42,36,32,38 / 40,32,35,34 / 25,28,29,31 / 36,30,32,28 / 40,38,34,44. The distribution uniformity for the irrigation is
Options:
(A) 80.4
(B) 81.9
(C) 87.9
(D) 88.1
Official Answer Key:
B
Step-by-Step Solution & Explanation
Christiansen's Distribution Uniformity DU = (average of the lowest quarter of observations / average of all observations) × 100. n = 20 readings; lowest quarter = 5 readings. Sorted ascending, the lowest 5 are 25, 28, 28, 29, 30 → mean = 28.0 mm. Overall mean of all 20 values = 34.2 mm. DU = 28.0/34.2 × 100 = 81.9%.
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