Section 4: Soil and Water Conservation Engineering
Fluid Mechanics
Subtopic: Flow in open channels
Question Statement:
A 50 km long canal with an average width of 25 m is used for irrigation. Mean daily evaporation as measured from a Class A evaporation pan is 5 mm d⁻¹. Considering the pan coefficient as 0.80, the mean daily evaporation loss from this canal is
Options:
(A) 5.00 × 10³ m³ d⁻¹
(B) 6.25 × 10³ m³ d⁻¹
(C) 5.00 × 10⁴ m³ d⁻¹
(D) 6.25 × 10⁴ m³ d⁻¹
Official Answer Key:
A
Step-by-Step Solution & Explanation
Actual (canal) evaporation = pan evaporation × pan coefficient = 5×0.80 = 4 mm/d = 0.004 m/d. Canal surface area = 50,000 m × 25 m = 1.25×10⁶ m². Loss = area × depth = 1.25×10⁶ × 0.004 = 5.00×10³ m³/d.
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