What happens when groundwater extraction decreases water pressure in aquifers?

When groundwater extraction decreases water pressure in aquifers, one significant consequence is the movement of saltwater inland, particularly in coastal areas. Aquifers, especially those located near coastlines, can be affected by saltwater intrusion when there is a drop in groundwater levels. This drop reduces the natural pressure that keeps saltwater from encroaching into freshwater aquifers.

As freshwater is extracted, the hydraulic gradient changes, and the balance between freshwater and saltwater can be disrupted. Saltwater from the ocean can then move further inland, contaminating the aquifer and making the water unsuitable for drinking and irrigation purposes. This phenomenon is especially concerning in regions where groundwater is heavily relied upon for agricultural and domestic uses.

Thus, the correct choice highlights a critical environmental issue associated with unsustainable groundwater use.