The intrusion of salty ocean water into aquifers due to excessive groundwater extraction in coastal cities is called what?

Correct answer: Saltwater intrusion

Correct answer: B, saltwater intrusion. In a coastal aquifer, fresh groundwater normally exerts pressure toward the sea and helps prevent seawater from moving inland. Excessive pumping lowers the freshwater table and reduces that protective pressure. Because seawater is denser, the saltwater–freshwater boundary can then move landward or upward toward wells. The result is salinisation of the aquifer, making the water unsuitable for many domestic, agricultural and industrial uses. Option A, soil leaching, is the downward washing of soluble substances through soil and is not the name of seawater entering an aquifer. Option C is water flowing over the land surface. Option D describes subsurface movement, but it is not the specific process and does not explain the salt contamination. Cue: over-pumping near the coast invites saltwater inland.