Send us Fan Mail Water seems to many of us like an unlimited resource, what with oceans covering 71% of the Earth’s surface. But less than 3% of the world’s water is fresh, and nearly a third of that is groundwater, found deep beneath the surface in aquifers between soil and rock. Many of the world’s aquifers are drying up as we over-pump them for irrigation, drinking water, and industrial uses. Does the depletion of groundwater pose an existential threat to humanity? Joe and Mark slosh aroun...