Hydrologic yield concept: In basin water resources assessment, the “yield of a drainage basin” generally refers to which quantity?

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:

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.