In 1904, just after the first airplane flight, the Texas Supreme Court ruled that groundwater was “too secret, occult, and concealed” to regulate. More than a century later, even with the ability to measure and monitor aquifer levels from space and with a growing body of scientific knowledge that aquifers are dangerously overstressed, an attitude of neglect is leading to groundwater crises in many of the world’s largest cities, most productive farmland, and most conflict-prone regions.

Groundwater is the most abundant source of liquid freshwater on the planet. Aquifers hold at least 25 times the water as rivers, lakes, and streams. Roughly two billion people rely on groundwater as a primary source of drinking water and nearly half the water used to irrigate crops comes from underground.

Yet despite its importance, groundwater is being used recklessly. Aquifer levels are plummeting in the grain belts of China and India. The Ogallala Aquifer, which gives life to America’s Great Plains, will be largely tapped out by the end of the century, at current rates of use. Parts of Indonesia’s capital, Jakarta, home to 10 million, sank 13 feet in a generation because so much groundwater was pumped that the land collapsed. Coastal cities and farmers are finding more salts in their wells as the ocean pushes inland. Groundwater in Bangladesh polluted with naturally occurring arsenic has been called the largest mass poisoning in history, with some 100 million people at risk.