How does withdrawing groundwater faster than an aquifer can recharge threaten water supplies?

Withdrawing groundwater faster than an aquifer can naturally recharge—a practice known as groundwater mining—poses significant threats to water supplies. When extraction exceeds the rate of replenishment, the water table drops, leading to several critical consequences:12

• Resource Depletion: As water levels fall, it becomes increasingly expensive and difficult to pump water to the surface. Eventually, this can cause wells and rivers to dry up entirely.132
• Saltwater Intrusion: In coastal areas, the decline in fresh water pressure allows saltwater intrusion to occur. Seawater infiltrates the aquifer, contaminating the supply and rendering wells unusable for drinking or irrigation.43
• Land Subsidence: The extraction of groundwater can cause subsidence, or the sinking of the Earth’s surface, as the removal of water leads to the compaction of sediment layers.5

Managing these systems requires a careful understanding of recharge processes to ensure that extraction remains within sustainable "safe yields," preventing the long-term loss of these vital freshwater resources.3