About 1.7 billion people rely on aquifers that are rapidly being depleted and would take thousands of years to refill, according to a new study in the journal Nature.

The report, "Water balance of global aquifers revealed by groundwater footprint," identifies aquifers in the U.S., Mexico, Eastern Europe, the Middle East, India and China as crisis zones where groundwater resources and/or groundwater-dependent ecosystems are under threat because the use of water vastly exceeds the rate at which aquifers are being refilled by rain.

The underground reservoir in northwestern India, for instance, would need 54 times more rainfall to replenish the water that’s currently being used by farmers and the local population.

In the map below, the blue areas mark where rain can replenish the amount of water being used by humans. Orange or red areas indicate places where people draw out more for irrigation and drinking water than rain can refill.

The gray areas show the extent of the "groundwater footprint" by representing how much water people are drawing from the aquifers compared with how much water each holds.