We live on a parched planet. Farmers till arid pastureland and policymakers fret over empty reservoirs, dry rivers and thirsty cities. And that only scratches the surface – literally – of the world’s water problem. Subterranean aquifers, the world’s reserve water tank, are also running dry. The consequences could be dire, especially for water-stressed and fast-growing Asia.

These repositories of water located deep underground in permeable rock, soil or sand contain about 100 times the amount of water found on the Earth’s surface in streams, lakes, rivers and wetlands. If you’re in central Africa, South America or some parts of Europe, chances are you’re standing a few hundred feet above one.

The gap between water supply and demand – predicted to reach 40% by 2030 – will not be filled by surface water resources, so aquifers are being exploited more and more for agriculture, power generation and daily use in fast-growing cities.

About 30% of the world’s freshwater comes from aquifers, yet a third of the 37 largest aquifers studied by the University of California between 2003-13 were severely depleted, receiving little or no replenishment from rainfall.

Some of the most stressed aquifers are in the world’s driest regions such as Asia, up to 88% of which is water-stressed. South Asia accounts for half the groundwater used globally, but the continent’s aquifers – many of which were formed millennia ago when areas like northern China had a more humid climate – are no longer being replenished regularly by rainfall.

Boreholes are getting deeper and water tables are falling. In Pakistan’s Punjab province, over-pumping is lowering the water table by up to a half a metre per year, threatening food and water security and making thirsty crops, such as sugarcane and rice, tougher to grow.

Asia’s surging population – which could top 5 billion by 2050 – will put even more stress on food, energy and water supplies. Globally, 60% more food will be needed by then, with agriculture using up increasingly scarce freshwater. Climate change will exacerbate conditions further.

But the problem extends beyond water depletion. Over-pumping groundwater leads to soil subsidence, causing some Asian cities to sink. By 2030, 80% of North Jakarta could be below sea level, while parts of Beijing are sinking by several centimetres a year. Depleted aquifers near coastlines are prone to contamination from saltwater, rendering land barren. Some are contaminated by arsenic, which can occur naturally deep underground.

The first step towards remedying this situation is to establish how much groundwater is left and how it is being used. This is not easy, but it’s not impossible either. Nasa’s Gravity Recovery and Climate Experiment satellite provides information on changes in the Earth’s gravity due to fluctuating water volumes. By applying remote sensing technology to river basins, we can determine how much surface water is available, and who is consuming what.



Another important step is to improve the pricing of groundwater. China has run a pilot program in which farmers had to pay extra if they pumped more than their allocation. Similar approaches have worked well in Australia and Mexico but such measures can be politically difficult to implement. The key will be to help countries design the right policies and create the legal frameworks needed to establish and enforce them.

Even more politically difficult would be to eliminate electricity and gas subsidies, which encourage farmers to pump groundwater all day. If such subsidies can’t be withdrawn, innovative alternatives could curb over-pumping. In Gujarat, for example, groundwater pumping has been reduced by offering power for just eight hours per day. Farmers have the power they need, but can’t pump all day long, and can sell surplus power back to the grid.

Efforts to replenish aquifers could also be pursued. A pilot program in Uttar Pradesh collects excess floodwater in storage ponds, from which water seeps into the water table.

The final step would be to improve the management of surface water, thereby reducing the temptation to turn to groundwater in the first place. About 80% of wastewater is returned untreated to rivers, often contaminating them. Taking stronger action to stop this would be far simpler – including logistically and politically – than conserving groundwater.

Aquifers should be the reservoir of last resort. If we don’t protect them today, future generations will pay a steep – or even an existential – price.

Copyright: Project Syndicate, 2017.

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