Step 1: Recall how confined aquifers support the ground above them.
Part of the weight of the overlying soil is carried by the pressure of the water inside a confined aquifer.
Step 2: Think about heavy, sustained pumping.
Drawing out far more water than is naturally replaced, called overdraft, lowers that internal water pressure.
Step 3: See what happens to the ground.
With less pressure support, the aquifer's solid grains compress and pack closer together, and this compaction shows up at the surface as land subsidence, unlike flooding, recharge, or rainfall which do not compress the aquifer skeleton.
\[ \boxed{\text{Overdraft in confined aquifers}} \]