1. The double-mass-curve technique is used to:
Correct Answer: c) Check data consistency
The double-mass curve is a graphical method used to check the consistency of rainfall data by comparing cumulative values from a test station with those from a reference station. Inconsistencies (like changes in instrument location or exposure) appear as breaks in the curve's slope.
2. A hyetograph plots:
Correct Answer: b) Rainfall intensity vs. time
A hyetograph is a graphical representation of rainfall intensity (y-axis) against elapsed time (x-axis). It's crucial for analyzing storm patterns, designing drainage systems, and flood forecasting.
3. The standard Symon's rain gauge has a collecting diameter of:
Correct Answer: a) 12.7 cm
The standard Symon's rain gauge features a 12.7 cm (5 inch) diameter collector funnel that directs rainfall into a measuring cylinder. This size provides a good balance between measurement accuracy and wind effects.
4. Orographic precipitation occurs due to air masses lifted by:
Correct Answer: c) Mountain barriers
Orographic precipitation results when moist air is forced upward by topographic barriers. As air rises, it cools adiabatically, leading to condensation and precipitation on windward slopes (e.g., Western Ghats in India).
5. If snowfall density is unknown, the water equivalent is assumed as:
Correct Answer: c) 10%
When snow density isn't measured, engineers assume 10% water equivalent (10 cm snow ≈ 1 cm water). Actual density varies (3-20% for fresh snow, up to 50% for settled snow).
6. The normal onset of monsoon in India begins in:
Correct Answer: b) Early June in Kerala & Assam
The southwest monsoon typically reaches Kerala around June 1st and Assam by early June, then progresses northwestward. Mumbai receives rains by mid-June, while Chennai gets most rainfall from the northeast monsoon (Oct-Dec).
7. The maximum rainfall intensity at a given location:
Correct Answer: b) Decreases with duration
Maximum rainfall intensity follows an inverse relationship with duration - short bursts (e.g., 5-min) have higher intensities than longer periods (e.g., 24-hr). This principle is fundamental in Intensity-Duration-Frequency (IDF) curves.
8. An isohyet is a line joining points with:
Correct Answer: d) Equal rainfall depth
Isohyets are contour lines of equal precipitation used to create rainfall distribution maps. The isohyetal method is considered more accurate than Thiessen polygons for uneven gauge distributions.
9. Which rain gauge produces a mass curve of precipitation?
Correct Answer: c) Weighing-bucket type
Weighing-bucket gauges record cumulative precipitation (mass curve) by measuring the weight of collected precipitation over time. Tipping-bucket gauges provide intensity data but not true mass curves.
10. A chart from a recording-type rain gauge typically provides:
Correct Answer: a) Mass curve of rainfall
Recording gauges (like weighing-bucket types) produce mass curves showing cumulative rainfall vs. time. Hyetographs (intensity vs. time) are derived by calculating slopes from mass curves.
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