The 'pan coefficient' used when converting Class A pan evaporation to lake evaporation accounts for:
Choose the correct answer
Different rainfall in lake vs pan
Pan overheats relative to large water body — pan evaporation > lake evaporation by factor of ~1/0.7 = 1.43
Wind speed difference only
Color of the pan
Correct Answer
B. Pan overheats relative to large water body — pan evaporation > lake evaporation by factor of ~1/0.7 = 1.43
Why is this the answer?
Pan coefficient Kp = Lake evaporation / Pan evaporation ≈ 0.7–0.8. Pan coefficient < 1 because: (1) Pan water heats more than lake (less mass, more exposed metal surface); (2) Reflected heat from pan edges increases evaporation; (3) Turbulence differs. IS 5973: Kp = 0.7 for well-maintained land pan. Multiply pan reading by Kp to get lake evaporation.
Related Hydrology MCQs
More solved Hydrology questions for AE/JE Civil Engineering exams.
- The 'SCS Curve Number' (CN) method for estimating runoff uses CN values that depend on:
- The 'design storm' for urban drainage uses IDF (Intensity-Duration-Frequency) curves...
- If the coefficient of variation of the rainfall values of the existing rain-gauge...
- If base period is 150 days and delta is 0.6 m, duty is
- For base period 120 days and duty 600 ha/cumec, delta is
- Darcy's law for groundwater flow states that the discharge velocity (Darcy flux) v...
Practice more Civil Engineering questions
This MCQ belongs to JE Level Premium Test Series. Full tests include timed attempts, rank comparison and subject-wise analysis.