A river basin of 4000 km² receives an average annual rainfall of 1200 mm. If the runoff coefficient is 0.5, what is the total annual runoff volume in cubic metres?
Answer
2.4 × 10^9 m³
The correct answer is 2.4 × 10^9 m³ — The answer is 2.4 × 10^9 cubic metres.
Step-by-step solution
- Convert the rainfall to metres: 1200 mm = 1.2 m.
- Convert basin area to square metres: 4000 km² = 4000 × (10^6) m² = 4.0 × 10^9 m².
- Calculate the total rainfall volume over the basin: 4.0 × 10^9 m² × 1.2 m = 4.8 × 10^9 m³.
- Multiply by the runoff coefficient to get the annual runoff volume: 4.8 × 10^9 m³ × 0.5 = 2.4 × 10^9 m³.
- The answer is 2.4 × 10^9 cubic metres.
Common mistake: Using rainfall in mm directly without converting to metres
Concept tested: Runoff volume calculation
Published · How this solution was prepared and checked
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