Global Water Reserves in 21st Century

Map of Global Aquifiers in the 21st Century

Researchers at McGill and Utrecht University in the Netherlands have recently published a map showing the regions where the use of water from these aquifers vastly exceeds the rate at which they're being refilled by rain. 

The map compares the usage footprint with the actual rainfall a particular aquifer gets. Blue areas receive more rain than is being used up by humans. For example, Russia has plenty of freshwater. But orange or red areas indicate places where irrigation and drinking water use is drawing out more water from the aquifers than the rain can refill.

Water is limited
 
Nature has decreed that the supply of water is fixed. Meanwhile demand rises inexorably as the world's population increases and enriches itself. Homes, factories and offices are sucking up ever more. But it is the planet's growing need for food (and the water involved in producing crops and meat) that matters most. Farming accounts for 70% of withdrawals.

Few of the world's great rivers that run through grain-growing areas now reach the sea all the year round or, if they do, they do so as a trickle. Less obvious, though even more serious, are the withdrawals from underground aquifers, which are hidden from sight but big enough to produce changes in the Earth's gravitational field that can be monitored by NASA's satellites in space. Water tables are now falling in many parts of the world, including America, India and China.

But there are many potential solutions
 
Although the supply of water cannot be increased, we can use what there is better—in four ways. One is through the improvement of storage and delivery, by creating underground reservoirs, replacing leaking pipes, lining earth-bottomed canals, irrigating plants at their roots with just the right amount of water, and so on. A second route focuses on making farming less thirsty—for instance by growing newly bred, perhaps genetically modified, crops that are drought-resistant or higher-yielding. A third way is to invest in technologies to take the salt out of sea water and thus increase supply of the fresh stuff. The fourth is of a different kind: unleash the market on water-users and let the price mechanism bring supply and demand into balance. And once water is properly priced, trade will encourage well-watered countries to make water-intensive goods, and arid ones to make those that are water-light. It is too early to tell how we will decide to manage our global water reserves.