2.
Identify the correct statements from the following :
The storage coefficient of an aquifer is :
(a) Attributable to compressibility of the aquifer skeleton and the pore water
(b) Attributable to the compressibility of the aquifer skeleton and expansibity of the pore water
(c) Attributable to the expansibility of the aquifer skeleton and the pore water
(d) The volume of water released or taken into storage from a vertical column of aquifer of unit cross-sectional area due to unit change in piezometric head
Exam Year(s)
MH SET - 2021, SET Exam - 2021,
Answer: D
The key gives (b) and (d).
Statement (d) is the definition of the storage coefficient (storativity): the volume of water an aquifer releases from, or takes into, storage per unit area for a unit change in head. Statement (b) is the usual account of where that water comes from in a confined aquifer: when the head falls, the aquifer skeleton is compressed and the pore water expands slightly, and the two together release water.
Statement (c) is wrong because the skeleton is compressed, not expanded, when pore pressure falls. Options A, B and C each include (a) or (c) in a pairing the key does not accept.
What could not be confirmed: statement (a) speaks of the compressibility of the pore water, which is the property the groundwater formulas use for water, so (a) is a looser wording of the same physics as (b) and option C ((a) and (d)) cannot be ruled out on physical grounds. D is taken because (b) repeats the textbook phrasing, compression of the skeleton and expansion of the water, and it is the keyed answer.
