Environmental science · Grades 9–12
Runoff in a simplified catchment
Use a uniform rainfall event and a stated constant runoff fraction. Real catchments require more detailed models.
Method and conditions
Use a uniform rainfall event and a stated constant runoff fraction. Real catchments require more detailed models.
V = rain depth × area × runoff fraction
Worked examples
Uniform rainfall of 89 mm falls on 12 hectares. In a simplified model, 0.6 of the rain becomes runoff. Find runoff volume in m³. Round the final result to 4 decimal places if needed. Answer in m³.
Convert mm to m and hectares to m²: (89/1000)(12×10000)(0.6).
6408 m³
Uniform rainfall of 139 mm falls on 58 hectares. In a simplified model, 0.9 of the rain becomes runoff. Find runoff volume in m³. Round the final result to 4 decimal places if needed. Answer in m³.
Convert mm to m and hectares to m²: (139/1000)(58×10000)(0.9).
72558 m³
Try it
Uniform rainfall of 91 mm falls on 29 hectares. In a simplified model, 0.1 of the rain becomes runoff. Find runoff volume in m³. Round the final result to 4 decimal places if needed. Answer in m³.
Uniform rainfall of 62 mm falls on 13 hectares. In a simplified model, 0.7 of the rain becomes runoff. Find runoff volume in m³. Round the final result to 4 decimal places if needed. Answer in m³.
Check your work
Answers and marking notes
- 2639 m³
Convert mm to m and hectares to m²: (91/1000)(29×10000)(0.1).
- 5642 m³
Convert mm to m and hectares to m²: (62/1000)(13×10000)(0.7).
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