Roughly a third of the world's freshwater withdrawals come from underground. In many agricultural regions the share is far higher, and during drought years groundwater becomes the buffer that keeps farms operating.
The problem is the recharge rate. Aquifers refill slowly, over years to millennia depending on geology. When extraction outpaces recharge, the storage declines, and the decline is often invisible until wells begin to fail.
What overdraft looks like
Water tables drop, so pumping costs rise. Shallow wells go dry, which affects small farms and rural households first. In some regions the land itself sinks as depleted layers compact, permanently reducing how much water the aquifer can ever hold again.
Coastal aquifers face an additional risk. As freshwater pressure falls, seawater moves inland, and once salt intrudes, reversing it is slow and expensive.
Why measurement is the first fix
Many groundwater systems are managed with limited data on how much is actually being withdrawn. Satellite gravity measurements have helped enormously at the regional scale, and local monitoring networks fill in the detail.
Measurement alone does not solve overdraft. But allocation debates that lack shared numbers tend to collapse into disputes about whose estimate is right, and that is a slow way to manage a resource that responds to decades of decisions.