Well hydraulics – definition used in many Indian texts In water-supply practice, the “specific yield of a well” is commonly taken to mean which of the following?

Introduction / Context:
Two similarly named terms often cause confusion: “specific yield” in aquifer storage (a volumetric property) and “specific capacity/yield of a well” in well hydraulics. Many competitive-exam texts in water-supply engineering use the latter meaning for operational well performance.

Given Data / Assumptions:

• Operational definition in water-supply design problems.
• Drawdown measured at the well under quasi-steady pumping.

Concept / Approach:
Specific capacity (sometimes called specific yield of a well) is defined as Q / s, where Q is discharge and s is drawdown at the well. It is used to compare wells and to extrapolate performance with different pumping rates.

Step-by-Step Solution:
Recognize context refers to well performance, not aquifer storage.Recall definition: specific capacity = discharge per unit drawdown.Choose the option that states “quantity of water per unit time per unit drawdown.”

Verification / Alternative check:
Field pumping tests routinely plot Q versus s; the slope near operating range gives specific capacity (units, e.g., L/s per m).

Why Other Options Are Wrong:

• (a) and (c) are storage quantities, not rates per drawdown.
• (b) is discharge only; drawdown dependence is missing.
• (e) is incorrect because (d) is the accepted performance metric.

Common Pitfalls:
Confusing aquifer “specific yield” (storage parameter) with well “specific capacity.” Always check context.

Final Answer:
Quantity of water per unit time per unit drawdown at the well (discharge per unit drawdown)