The world's natural aquifers at risk

Story Nov 06, 2018

A look at some of the most stressed aquifers on Earth and a snapshot of the reasons why "red flags" are being raised about the amount of water underground that’s declining amid population growth, urban, industrial and farming demand, and poor management.

In Sri Lanka, groundwater has taken on increased importance, with new wells being built. Photo: Dominic Sansoni/World Bank

By Randall Hackley – Originally appeared in Stockholm WaterFront Magazine 2018, issue #2

When scientists evaluating satellite-data say a third of the planet’s major aquifers are being unsustainably depleted, threatening groundwater reserves and putting ecosystems and life-sustaining water supplies at risk, perhaps it’s time to more seriously assess the global severity.

Here’s a look at some of the most stressed aquifers on Earth and a snapshot of the reasons why “red flags” are being raised about the amount of water underground that’s declining amid population growth, urban, industrial and farming demand, and poor management.

 

The Arabian aquifer system, whose groundwater accounts for about 84 percent of total freshwater use across the arid Arabian Peninsula, is among the most overstressed. There, a study showed 10 countries from Saudi Arabia to Iraq, Jordan, Yemen and Syria, are essentially at Ground Zero as the planet warms amid climate change: Almost 90 percent of the water withdrawn from the Arabian aquifer goes for agriculture, often paid for by oil revenues that subsidize the energy-intensive pumping of groundwater.

In a world in which two of five people, or 40 percent of the planet’s population, live in water-stressed areas, and weather extremes are making droughts more debilitating, the groundwater stored in aquifers is taking on increased importance. As the Los Angeles Times noted in a July op-ed piece, “The best place for California’s water is underground’’.

Indeed, California’s Central Valley aquifer system was sixth of the global “hotspots” of aquifer depletion in a 2016 report. The aquifer is almost liquid gold, supplying California’s agricultural breadbasket that provides 25 percent of the U.S. food and three-quarters of irrigated land in the state.

Over-pumping of the Central Valley aquifer, heavily depleted by irrigating thirsty crops such as almonds during droughts including California’s recent 5-year one, caused some roads and farmland to subside or sink several metres (feet), despite the system’s medium water recharge rate.

Farmers rely heavily on groundwater pumped from wells, from California and the U.S. Midwest, to Morocco, Spain and much of India. Increasing populations, including those migrating from rural, infrastructure-lacking areas to job-supplying cities, and the negative effects of climate change conspire to pressure groundwater supplies. At least 2 billion people of the 7.6 billion on Earth use groundwater as their primary source of water.

Growth and economic development in the most-populous nations, China and India, means both countries and their neighbours have transboundary aquifer systems at serious risk of depletion. Like parts of the Middle East and Asia, hydropolitical concerns affect Egypt and Ethiopia’s relations.

The Indus basin, for example, encompasses sections of India, Pakistan, Afghanistan and China. Some 300 million people, most of them in India and Pakistan, rely on its aquifer because almost all farms are irrigated, often with subsidized electricity and overused and unregulated water pumps. Agriculture accounts for about 92 percent of the Indus basin’s freshwater withdrawals. Studies show the water table in some areas of Pakistan has fallen as much as 20 feet (6 metres).

Similarly, the Ganges-Brahmaputra basin suffers aquifer depletion and groundwater pollution stresses that are only in part offset by its high annual recharge rates. The basin that includes swathes of India, China, Nepal, Bangladesh and Bhutan is home to about 10 percent of the planet’s population.

Bangladesh, where an estimated 97 percent of residents use wells for their drinking water, has degraded large areas of the aquifer system, exposing about 75 million people to arsenic pollution in the aquifer, studies show.

Research trying to quantify renewable groundwater stress using satellites measuring shifts in the total amount of water showed that close to 50 percent of the world’s aquifers may be “past their ‘tipping point’,” according to Henk Ovink, water envoy for The Netherlands. “Past their ‘tipping point’ means that a natural recovery has become impossible.’’

In Africa, the Northwest Saharan and Nubian aquifer systems are considered two of the larger underground water storage sites under stress.

The Nubian system, the biggest non-renewable aquifer in the world, flows under parts of Egypt, Libya, Sudan and Chad. Mostly underlying Egypt and Libya, it’s considered a high-stress site due to unsustainable withdrawal rates and demographic pressures. Libya depends on the aquifer for about 95 percent of its water.

The system also features one of the few transboundary aquifer agreements. Worldwide, six transboundary aquifers exist with specific agreements, and two aquifers with informal accords.

The Northwest Saharan aquifer system that underlies 60 percent of Algeria, almost a third of Libya and part of Tunisia is another transboundary aquifer with high levels of water withdrawals. It too features a cooperation pact and is similar to the Nubian system in being non-renewable. Its extraction pressures come mainly from agricultural irrigation and industry.

In Asia, the North China aquifer system has significant depletion pressures as agriculture uses almost two-thirds of its water and industry about a quarter amid land degradation issues in a region that includes the capital Beijing and about 11 percent of the Chinese population.

Northern China depends on groundwater for about half of its total water usage, mostly for agriculture and municipal demand. The South-North Water Diversion inter-basin transfer project to divert Yangtze River waters to the region is designed in part to help alleviate demand and water levels in non-renewable areas of the aquifer that have fallen drastically.

Water doesn’t always correspond easily to administrative or political boundaries so many aquifers are shared by two or more countries. Local water stress and climate change can then become “root causes for conflict and migration,” Ovink said by email. “We need to understand water in its complexity better, value it comprehensively and manage it at all scales and across all interests and layers of society and our institutions.”

Projections under current usage, global population pressures and growth scenarios suggest a possible 40 percent shortfall in water availability within just 12 years, including the almost 600 aquifers that cross sovereign borders.

Groundwater withdrawals already exceed groundwater availability — defined as groundwater recharges minus groundwater contributions to environmental stream flows — in about 20 percent of the planet’s aquifers, according to research. Almost 2 billion people reside in these areas.

In the past half-century, groundwater abstraction from such sites as the Caspian and Aral Sea areas to the U.S.’s over-utilized Ogallala aquifer has increased more than 300 percent, said Tales Carvalho-Resende, a water expert with UNESCO.

According to Arjen Hoekstra, who created the water footprint concept, about 22 percent of the water use in the world is for producing export products.

In the Ica-Villacuri aquifer beneath the Ica Valley desert in Peru, he noted, growers of asparagus that’s exported to European markets pump water from the aquifer for irrigation at a much faster rate than it can recharge.

Water depletion is not always obvious because groundwater, often unseen, is difficult to measure and monitor. More data to quantify the water underground and water-saving technologies such as Israel uses can help.

Water, after all, is mankind’s common currency. Water “touches nearly every aspect of development,” the UN says. “It flows through and connects the 17 Sustainable Development Goals (SDGs) by driving economic growth, supporting healthy ecosystems, cultivating food and energy production, and ensuring access to sanitation.”

Yet “water represents a silent emergency and a risk to our goals of building shared economic progress and sustainable development.’’

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