© Peter Essick, National Geographic
In ten years, the Colorado River Basin has lost the equivalent of two Lake Meads, the largest reservoir in the U.S., pictured here at dusk with Las Vegas in the background.
We're pumping irreplaceable groundwater to counter the drought. When it's gone, the real crisis begins.
Aquifers provide us freshwater that makes up for surface water lost from drought-depleted lakes, rivers, and reservoirs. We are drawing down these hidden, mostly nonrenewable groundwater supplies at unsustainable rates in the western United States and in several dry regions globally, threatening our future.
We are at our best when we can see a threat or challenge ahead. If flood waters are rising, an enemy is rushing at us, or a highway exit appears just ahead of a traffic jam, we see the looming crisis and respond.
We are not as adept when threats - or threatened resources - are invisible. Some of us have trouble realizing why invisible carbon emissions
are changing the chemistry of the atmosphere and warming the planet. Because the surface of the sea is all we see, it's difficult to understand that we already have taken most of the large fish from the ocean
, diminishing a major source of food. Neither of these crises are visible - they are largely out of sight, out of mind - so it's difficult to get excited and respond. Disappearing groundwater is another out-of-sight crisis.
Groundwater comes from aquifers - spongelike gravel and sand-filled underground reservoirs - and we see this water only when it flows from springs and wells. In the United States we rely on this hidden - and shrinking - water supply to meet half our needs
, and as drought shrinks surface water in lakes, rivers, and reservoirs, we rely on groundwater from aquifers even more. Some shallow aquifers recharge from surface water, but deeper aquifers contain ancient water locked in the earth by changes in geology thousands or millions of years ago. These aquifers typically cannot recharge
, and once this "fossil" water is gone, it is gone forever - potentially changing how and where we can live and grow food, among other things.