Engineering Hydrology Questions and Answers – Potential Evapotranspiration

This set of Engineering Hydrology Multiple Choice Questions & Answers (MCQs) focuses on “Potential Evapotranspiration”.

1. What are the lines joining places of equal evapotranspiration known as?
a) Isohyets
b) Isopleths
c) Isochrones
d) Isocline

Explanation: The lines drawn on map that join the places having equal depths of evapotranspiration for a given duration are known as isopleths. An isopleth map gives an idea of the evapotranspiration occurring in different areas of a region.

2. The aridity index is defined as the ratio of the actual evapotranspiration to the potential evapotranspiration, represented as a percentage.
a) True
b) False

Explanation: Aridity index is the ratio of the difference between the potential evapotranspiration and actual evapotranspiration to the potential evapotranspiration, expressed as a percentage.

3. What is indicated by the aridity index for a region?
a) Dryness
b) Humidity
c) Water availability
d) Sunshine hours

Explanation: The aridity index is a suitable indicator of the degree of dryness of a particular region. It gives an idea of the deficit of water in a particular region and helps to change the land use patterns accordingly. It is a common indicator of drought severity in India.

4. Which of the following is the most representative value of PET per year in the western region of India?
a) 2 mm
b) 20 mm
c) 200 mm
d) 2000 mm

Explanation: As per IMD (1971), the PET ranges form 140 cm to 180 cm per year over most of India. The higher values of PET are observed in the western region of Gujarat with average values of about 200 cm per year.

5. Let ‘A’ represent the aridity index and ‘B’ represent the rainfall of a region. How is ‘A’ related to ‘B’?
a) A∝B
b) A∝$$\frac{1}{B}$$
c) A+B=1
d) No relation

Explanation: For a given PET, if the AET of a region increases, the aridity index decreases. As the AET increases with increase in soil moisture content and soil moisture content is directly proportional to the rainfall, it implies that aridity index decrease as the rainfall increases.

6. A region with aridity index of 70% indicates which of the following?
a) No drought
b) Mild drought
c) Moderate drought
d) Severe drought

Explanation: The areas are classified based on the value of aridity index (AI) as,
AI (%) $$\begin{cases} ≤ 25 ⇒ mild \, drought \\ ∈(25,50) ⇒ moderate \, drought \\ ≥50 ⇒ severe \, drought \end{cases}$$

Sanfoundry Global Education & Learning Series – Engineering Hydrology.