Groundwater aquifers, like personal bank accounts, become insolvent when withdrawals exceed deposits.
Unlike bank accounts or water sources such as rivers, most of the world's aquifers don't fluctuate all that much from month to month, or even from year to year. You can think of them more like retirement savings accounts: steady, slow changes are usually the norm.
That slow motion makes it easy to read trends. If you see a downward trend in either your retirement account or your local aquifer, you could be headed for serious trouble.
More than 2 billion people depend on groundwater for drinking or growing food. Groundwater provides more than a quarter of all the water used in the world, with most of its use attributed to irrigated agriculture. Some countries are much more heavily dependent on groundwater than others. In India and the US, more than 60% of irrigated agriculture relies on it.
Groundwater also provides a very important buffer against water shortages caused by droughts. Because aquifer levels are considerably less susceptible to short-term climate fluctuations than surface waters such as rivers and lakes, groundwater can be used as a reserve when other water supplies are running short, much like taking out a short-term loan against your retirement fund.
The good news is that our ability to detect groundwater trends has increased remarkably in recent years. The bad news coming in from satellite observations and computer models is that the levels of many of the world's most important aquifers are dropping precipitously. Recently, studies have shown that 20% of irrigated agriculture, which produces 40% of our food, is reliant upon aquifers with falling water levels. We are increasingly living on borrowed water, with no repayment plan.
It takes a lot of pumping to lower the groundwater level in the world's larger aquifers, simply because they are so massive in volume. The Ogallala aquifer of the American mid-west stores as much water as Lake Huron in the Great Lakes chain, enough to cover the lower 48 states with more than a half a metre of water. The Nubian sandstone aquifer of northern Africa holds more than six times the water of the entire Great Lakes system – more than all the available freshwater on the surface of our planet.
Yet we have gained the technological capacity to drain them. Water levels in the Ogallala have dropped by more than 50 metres in some wells. While that equates to depletion of only 10% of the total volume, with groundwater it's the depth of water that matters, not how much water is left. That's because it takes an extraordinary amount of electricity to lift water as it gets deeper and deeper. As the water in a well drops from 10 to 100 metres in depth, electricity costs can easily increase by 10 times or more, making it economically infeasible to pump any more. That reality is driving thousands of farmers out of business every year.
Electricity is the ultimate regulator on overdrafts at the water bank. It's like paying compounding interest on borrowed money: with every year, the debt becomes greater and operation costs soar ever higher.
Five years ago, realising the madness of subsidising the burning of oil to pump groundwater from ever-deeper levels, Saudi Arabia abandoned its dream of wheat self-sufficiency. Wheat farming was consuming a third of all water used in the country, and virtually all of that water was coming from declining fossil (non-renewable) aquifers. The government will now import its wheat, leaving the remaining groundwater for its cities and industries.
Groundwater declines have been deadly for poor farmers in India. Millions of Indian farmers have witnessed their hand-dug wells going dry, and they cannot afford to chase the falling water level by digging deeper. More than a quarter of a million Indian farmers have committed suicide in the last 15 years. The rising cost of farm inputs such as electricity and the inability to irrigate their crops are among the leading causes.
The Indian government has tried to stave off water and food shortages by subsidising electricity costs. But across much of India that has only accelerated the rate of groundwater depletion.
Ultimately, the only way to stabilise our groundwater accounts is to stop withdrawals from outpacing the natural recharge of water.
You would think that sustainably managing and regulating our use of the planet's most precious resource would be a very high priority for our governments. But to date governments have proven miserably incapable of accomplishing such regulation. I have been paying close attention to global water issues for nearly 30 years now, and I still cannot point to a single country that has effectively stabilised its water accounts.
If governments can't or won't do this, who will save us from water bankruptcy?
I have come to the sobering but empowering conclusion that we must save ourselves and not wait for our governments to help us. We must learn, or in some cases, relearn, the art and culture of sharing water in our local watersheds and communities.
In the absence of strong governance, some local communities are taking matters into their own hands. For example, a community of farmers using the Ogallala aquifer in north-west Texas recently voted to place voluntary limits on their groundwater use as a means to arrest aquifer declines.
The practice of water sharing has some long lineages. We might look to the acequia culture that has evolved over the past 10,000 years, with roots in the Middle East that were spread into southern Spain by the Moors, and then by the Spanish into the American south-west. This communal system of water sharing and irrigating was a response to the scarcity of water in arid regions, and has been key to the survival of agricultural communities where it is practiced.
Advances in technology can certainly help. Farmers in the Flint river basin in the state of Georgia in the US are pushing the frontiers of irrigation efficiency, both to save on electricity costs as well as to sustain their community and a river they love.
Paul McCartney once wrote that " … in the end, the love you take is equal to the love you make."
The same can be said for water.
Brian Richter is director of global freshwater strategies at The Nature Conservancy