GATE AG 2012 • Q41 MCQ • 2 Marks

Section 5: Irrigation and Drainage Engineering

Groundwater Hydrology

Subtopic: Steady and unsteady flow in confined and unconfined aquifers

Question Statement:

A 200 mm well fully penetrates a confined aquifer. After long pumping at 1400 L/min, drawdowns in observation wells at 25 m and 40 m are 2.6 m and 1.9 m respectively. The transmissivity of the aquifer, in m²/day, is:

Options:

  • (A) 190
  • (B) 198
  • (C) 206
  • (D) 215

Official Answer Key:

D

Step-by-Step Solution & Explanation

Thiem (steady-state confined) equation: T = Q ln(r2/r1) / [2π(s1-s2)]. Q = 1400 L/min = 2.016 m³/h = 48.384 m³/day... wait, express in consistent units: Q = 1400 L/min × 1440 min/day = 2,016,000 L/day = 2016 m³/day. s1-s2 = 2.6-1.9 = 0.7 m. ln(40/25)=ln(1.6)=0.470. T = 2016×0.470/(2π×0.7) = 947.5/4.398 = 215.4 m²/day. Answer: D.

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