Explain how overpumping leads to water scarcity in coastal areas.

Overpumping is a process of extracting groundwater for various needs, mostly to supply water basins and aquifers. When it's near a coastal area, what can happen is that the salt water from the sea mixes with the regularly pumped water, which causes the old water to become salty and undrinkable too. This means that there's less usable water since the salt water can't be drunk.