Dupuit method for pumping-test analysis The classical Dupuit (Dupuit–Thiem) analysis for estimating aquifer parameters is based on observations from how many observation wells?

Introduction / Context:
The Dupuit–Thiem method is a steady-state approach to analyze radial flow toward a pumping well. It relies on piezometric head measurements at known radii to compute hydraulic conductivity.

Given Data / Assumptions:

• Horizontal, radial flow under Dupuit assumptions (small vertical gradients).
• Homogeneous, isotropic aquifer with steady pumping.
• Two observation wells located at known distances from the pumped well.

Concept / Approach:
With two observation wells, the logarithmic head–radius relationship can be written between radii r1 and r2, eliminating the unknown integration constant and directly solving for K using the observed heads.

Step-by-Step Solution:

Verification / Alternative check:
Using more than two wells provides redundancy and enables least-squares fitting to the theoretical straight line of head vs ln(r).

Why Other Options Are Wrong:

• One well cannot define the slope of the ln(r) relation.
• Three wells are useful but not the basis of the original formula.
• No observation well is impossible for parameter estimation.

Common Pitfalls:
Placing observation wells too close to the pumping well (well losses dominate) or near boundaries which distort radial symmetry.

Final Answer:
Two observation wells