Question

The specific capacity of a confined well under equilibrium condition and within the working limits of drawdown ______________

(a) is constant at all drawdowns

(b) decreases as the drawdown are increased

(c) increases as the drawdown are increased

(d) may increase or decrease

The question was posed to me during an interview for a job.

The origin of the question is Aquifers and Their Type-2 topic in section Ground Water for Irrigation through Wells and Tubewells of Irrigation Engineering

Answer 1

The correct choice is (b) decreases as the drawdown are increased

The best explanation: The following equation shows that specific capacity decreases as Q increases and Q increase only when the drawdown is increased by heavier pumping and hence, specific capacity decreases as drawdown is increased.

Specific capacity = Q/(C1.Q + C2.Q^2). i.e. Discharge/ Drawdown (Well loss + Aquifer loss).