Hydrologic yield concept: In basin water resources assessment, the “yield of a drainage basin” generally refers to which quantity?
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ARunoff expressed as an instantaneous rate at a given moment
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BAverage runoff over a short storm period only
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CTotal volume of water flowing from the basin over an entire year
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DAll the above
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ENet infiltration volume during monsoon season
Answer
Correct Answer: Total volume of water flowing from the basin over an entire year
Explanation
Introduction / Context:The term “yield” is used in water resources to indicate dependable water available from a catchment, commonly over an annual period. Correctly identifying yield is crucial for planning reservoirs, water supply allocations, and irrigation schemes.
Given Data / Assumptions:
- Yield is related to runoff leaving a defined catchment boundary.
- We consider the hydrologic (not economic) definition.
Concept / Approach:
Annual yield is the accumulated discharge volume over a hydrologic year. It integrates baseflow and quickflow from all events, making it the relevant quantity for long-term resource planning rather than momentary or short-period rates.
Step-by-Step Solution:
Identify time scale: annual (entire year).Define yield = ∫Q(t) dt over the year.Select the option stating “total volume annually.”Verification / Alternative check:
Reservoir safe yield and firm yield analyses begin from the annual runoff series, not instantaneous values.
Why Other Options Are Wrong:
- Instantaneous rate: A flow rate, not a yearly volume.
- Short-period average: Inadequate for annual planning.
- Net infiltration volume: Not the same as basin yield at the outlet.
Common Pitfalls:
- Confusing “yield” with “peak discharge.”
- Ignoring inter-annual variability and dependability analysis.
Final Answer:
Total volume of water flowing from the basin over an entire year.