Definition of basin yield and runoff terms Pick the correct statement about “yield” of a drainage basin and how runoff is expressed.
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AYield of a drainage basin is the runoff at any single moment in time
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BYield of a drainage basin is the runoff evaluated over long periods (e.g., annual or multi-year totals)
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CYield of a drainage basin is always expressed only as surface runoff per year
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DRunoff is always expressed as total volume per day regardless of context
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ENone of these
Answer
Correct Answer: Yield of a drainage basin is the runoff evaluated over long periods (e.g., annual or multi-year totals)
Explanation
Introduction / Context:Hydrologists distinguish between instantaneous discharge, event runoff, and long-term yield. Correct terminology prevents confusion in water-resources planning.
Given Data / Assumptions:
- “Yield” refers to a long-term average or accumulated runoff from the basin.
- Runoff can be expressed as depth, volume, or discharge depending on context.
Concept / Approach:Yield typically means the dependable or average quantity of water produced by a basin over a specified period (e.g., annual yield). Instantaneous measures (hydrograph ordinates) do not represent yield.
Step-by-Step Solution:
Identify “yield” as a long-term metric: option (b).Reject statements that fix units or time scales universally for runoff.Verification / Alternative check:Textbooks define yield as long-term runoff availability; project reports quote annual yield or firm yield based on storage–yield analysis.
Why Other Options Are Wrong:
- (a) confuses yield with instantaneous discharge.
- (c) overly restricts yield to surface runoff only; baseflow contributes too.
- (d) imposes a single unit/time scale on runoff, which varies by application.
Common Pitfalls:Using peak discharge to represent basin yield; they are different metrics for different design questions.
Final Answer:Yield of a drainage basin is the runoff evaluated over long periods (e.g., annual or multi-year totals)