Almonds, grapes, cotton, and apricots: all crops that California’s Central Valley is famous for. But three years of drought have taken their toll, and farmers have had to drill deeper wells and pump more groundwater to prevent their crops from wilting.

A recent survey by the U.S. Geological Survey shows that in California's Tulare Basin, groundwater levels have dropped by as much as 50 feet (15 meters) over those three years. The water table is likely to take decades to recover.

Groundwater—the water stored in underground cracks and pores in rocks and soil—represents just 1.7 percent of Earth’s total water, yet groundwater accounts for over 30 percent of all freshwater. Almost all of the remaining freshwater is locked up in ice