Beneath our feet lies a hidden treasure: groundwater.
Spread across the world in vast aquifers – rock and sediment layers that act like an underground reservoir – these water reserves constitute 99 percent of the world’s liquid freshwater and support countless communities and ecosystems. But according to a new report, groundwater tends to be either undervalued, over-exploited or polluted due to human activity.
This year’s U.N. World Water Development Report, “Groundwater: Making the invisible visible,” details the state of the world’s groundwater and introduces effective management practices. Its publication by the U.N. Education, Scientific and Cultural Organization (UNESCO) on behalf of U.N. Water coincides with World Water Day and the opening ceremony of the 9th World Water Forum taking place in Dakar, Senegal.
“Making smarter use of the potential of still sparsely developed groundwater resources, and protecting them from pollution and over-exploitation, is essential to meet the fundamental needs of an ever-increasing global population and to address the global climate and energy crises,” said Audrey Azoulay, the Director-General of UNESCO, in a press release.
Groundwater makes up around half of the water used by the global population for domestic purposes and a quarter of all water used for irrigation. The report states that half of the world’s urban population is also dependent on this water resource. Usually extracted by wells, groundwater does not require the same level of treatment compared with other water sources and is often the most affordable water supply for rural communities.
But many regions are already experiencing water shortages, and the demand for water is expected to grow by 20 to 30 percent by 2050 due to a growing human population that is projected to cause a 50 percent increase in food, feed and biofuel needs by 2050 (compared with 2012 levels). Climate change is likely to exacerbate this shortage, as a hotter atmosphere will speed up the evaporation of surface water, such as that found in lakes and reservoirs.
What groundwater we have
Richard Taylor, a professor of hydrogeology at University College London and an author of the report, said in an email that the supply of groundwater itself could be affected by climate change because of shifts in the precipitation needed to replenish aquifers, a higher risk of contamination due to heavier rainfall events flushing substances from human activity (such as sewage) below ground, salinization of coastal groundwater as sea levels rise and storm surges worsen, and a growing reliance on water from below the ground to fulfil a greater freshwater demand when less frequent rainfall dries out the soil.
And indeed, groundwater has been over-used in some regions, such as in Northern India and the U.S. The vast majority of extracted groundwater – 70 percent – is used for irrigation agriculture. Aquifers accumulate water over years, decades or even millennia, typically from excess surface water that seeps into the ground from rainfall. This then provides water for many rivers and water holes in arid ecosystems, such as savannas. Thus, a rapid depletion of groundwater could harm both people and the ecosystems that depend on it.
Aquifers can also be polluted, a process that is practically irreversible. A major source of pollution is agricultural fertilizers or pesticides, which can trickle through the soil into groundwater resources. Ingestion of nitrates, a common component of fertilizer, in drinking water can be carcinogenic. A wide range of pollutants from industrial processes, mining and fossil fuel extraction, as well as from urban settlements that lack sanitation services, can also contaminate aquifers.
What groundwater is yet to come
On the flip side, the report notes that some regions have under-utilized their groundwater reserves. Almost 400 million people in sub-Saharan Africa lack access to basic drinking water, even as the region sits on a vast supply of untapped groundwater. The volume of its stored groundwater is estimated to be 100 times greater than the annual renewal of its freshwater resources, including that from rainfall. Nevertheless, only 3 percent of the region’s farmland is irrigated, and of that, only 5 percent uses groundwater.
This untapped potential, according to the authors, is the result of a lack of groundwater infrastructure, experts and knowledge in the region. Yet investing in these could boost the economy by improving agricultural yields and help sub-Saharan Africa adapt to a heating planet by providing a stable supply of freshwater.
“This region could potentially make very substantial gains in securing climate-resilient access to safe water for drinking, irrigation and industry through equitable, prudent, and sustainable development of groundwater resources,” said Taylor, who added that the last decade has seen a push toward developing groundwater infrastructure through programs like the Pan-African Groundwater Program and Unlocking the Potential of Groundwater for the Poor (UPGro).
So what needs to be done for groundwater to be used sustainably? A lot more data, says the report, which states that monitoring for this water resource is often neglected by national and local governments. However, there is opportunity to gain support from the private sector, such as through fossil fuel and mining companies that conduct extensive underground surveying and can collect data on aquifers in the process. Providing such data to the public sector could be a part of their corporate social responsibility programs.
“A lack of data does not mean necessarily that data does not exist,” said Claudia Ruz Vargas, a researcher at the International Groundwater Resources Assessment Centre and an author of the report. She noted that, on top of a lack of groundwater data in poor countries, not all data collected either by governments or private companies is available to the public, and information can be “discontinuous and dispersed among institutions.”
Individuals can also be enlisted to help gather data on and monitor groundwater resources through citizen science initiatives. These, along with the incorporation of local knowledge and remote sensing technology, can supplement existing monitoring networks. Vargas said that technological innovations like telemetry, the collection and transmission of data from remote points, can also help to monitor difficult-to-access points more frequently.
The report’s authors stress that governments should apply themselves as custodians of this water as a common good. Given this view, access to and profit from groundwater should be distributed equally within communities and managed so that it can be enjoyed by later generations. Good land-use practices and strong environmental protection must also be practiced to prevent groundwater contamination, particularly in areas where aquifers recharge.
To achieve this, the report’s authors urge decisionmakers to include more groundwater professionals within institutions and governments and better support agencies’ mandates and financing. Such initiatives should be reflected in government budgets, along with an end to subsidies that encourage the depletion of aquifers, such as those incentivizing agriculture to grow crops with high water demands.
“We often say that groundwater is an invisible resource. But in my view, this is true only for politicians and policymakers: people that rely on groundwater understand perfectly well when they run out of water, or when they get ill because of drinking polluted water,” said Ruz Vargas. “The reliance on groundwater is increasing as surface water resources become less available, but what is the plan for when we also run out of groundwater?”
The U.N. World Water Development Report is U.N. Water’s main publication on water and sanitation issues. It focuses on a different theme every year, with the valuation of water being the topic of last year’s report. Its production is coordinated by the UNESCO World Water Assessment Programme.