Subtopic: Steady and unsteady flow in confined and unconfined aquifers
Question Statement:
Which of the following assumptions form the theoretical basis of the Theis non-equilibrium equation for radial unsteady flow to a pumping well in a confined aquifer?
Options:
(A) The aquifer is homogeneous, isotropic, of uniform thickness, and of infinite horizontal areal extent
(B) The pumping well fully penetrates the aquifer and has an infinitesimal radius (line source)
(C) The discharge rate from the well is held strictly constant throughout the pumping duration
(D) Water removed from storage is released instantaneously with a decline in hydraulic head
Answer Key:
A, B, C, D
Step-by-Step Solution & Explanation
All four assumptions are the fundamental axioms formulated by C.V. Theis (1935):
- A: Constant transmissivity $T = K b$ in all radial directions without boundaries.
- B: One-dimensional horizontal radial flow without vertical convergence.
- C: Constant discharge $Q$.
- D: Instantaneous elastic release governed strictly by storage coefficient $S$ without delayed drainage.