A fully penetrating artesian well is pumped at a rate Q = 1500 m³/day from an aquifer whose storage coefficient and transmissivity are 4 × 10⁻⁴ and 0·145 m²/min, respectively. Considering w(u) = 8·62, what is the drawdown at a distance 3 m from the production well after one hour of pumping ?
- A8·62 m
- B14·53 m
- C4·93 mCorrect
- D2·38 m
Solution
Concept
Theis drawdown in a confined aquifer
Formula
s = Q W(u) / (4π T)
Step-by-step solution
1. T = 0.145 m²/min = 208.8 m²/day. 2. s = 1500 × 8.62 / (4π × 208.8) = 12 930 / 2623.9 = 4.93 m.
Explanation
The Theis solution gives the drawdown at a given distance and time using the well function W(u).
Why the other options are wrong
8.62 m is W(u) itself, and the others do not equal QW/(4πT).
Shortcut
Convert T to m²/day before using Q in m³/day.
Common mistake
Forgetting to convert minutes to days.
Correct answer: C) 4·93 m