Allied & ICAR Exam Bank • ALLIED_1163 NAT • 2 Marks

Section 4: Soil and Water Conservation Engineering

Hydrology and Runoff

Subtopic: Thiessen Polygon Method

Question Statement:

A watershed has 3 rain gauge stations $A, B, C$ with Thiessen polygon areas of 20 km$^2$, 50 km$^2$, and 30 km$^2$, respectively. If recorded storm rainfalls are $60\text{ mm}$, $80\text{ mm}$, and $100\text{ mm}$, the average catchment precipitation in mm is:

Answer Key:

82

Step-by-Step Solution & Explanation

Total area $= 20 + 50 + 30 = 100\text{ km}^2$. Average rainfall $P = \frac{(20 \times 60) + (50 \times 80) + (30 \times 100)}{100} = \frac{1200 + 4000 + 3000}{100} = \frac{8200}{100} = 82\text{ mm}$.
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