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World Water Day 2022: Groundwater, making the invisible visible

If we think about the water cycle, the phrase "Heaven is under our feet as well as over our heads" by American writer and philosopher Henry David Thoreau was never truer. Within the hydrosphere, water travels from the earth's surface to the sky (evapotranspiration), then falls back down (precipitation), spreads over the continental surface (runoff), and finally enters the soils and rocks beneath our feet (infiltration) until it reaches the groundwater.

World Water Day 2022 is precisely about groundwater, which, with the theme "Groundwater: making the invisible visible", seeks to highlight the importance of the water which, beneath our feet and invisible to our eyes, is the basis that sustains the economic, social and environmental development of communities and, therefore, plays a fundamental role in adapting to climate change. In fact, climate change is felt through water, whether it is excess water through flooding in some places or water scarcity in others, where groundwater may be the only source of water available to the population.

Although groundwater is invisible, its impact is visible everywhere, as it supports drinking water supplies, sanitation systems, farming, industry and ecosystems. We must not forget that almost all of the liquid freshwater in the world is groundwater, making it the second-largest freshwater reserve on the planet. 

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For all these reasons, the UN calls for exploring, protecting and sustainably using groundwater to survive climate change and meeting the needs of a growing population on this year's World Water Day. For many, however, these waters remain largely unknown. “Groundwater is out of sight, but we cannot afford for it to be out of mind.  Stored in rocks and soil, groundwater is our biggest source of liquid freshwater. It sustains drinking water supplies, sanitation systems, farming, industry and ecosystems. Yet, some 20 per cent of the world’s aquifers are being overexploited,” says António Guterres, UN Secretary-General.

Groundwater, largely unknown

Little is known about groundwater despite being the most abundant freshwater resource on the planet. They are also largely forgotten by the authorities despite being a necessary resource for the socioeconomic development and environmental preservation of a country.

Groundwater is the great unknown despite being the most abundant freshwater resource on the planet

According to the International Groundwater Resources Assessment Center (IGRAC), which promotes and facilitates the international exchange of information and knowledge needed for groundwater resources development and sustainable management worldwide, groundwater currently provides half of the volume of water withdrawn for domestic use by the world's population, about 40% of the water for irrigated agriculture, and about one-third of the water needed for industry. While great progress was made in groundwater monitoring in 2021, the status of aquifers (both groundwater quality and quantity) changes over time due to changing environmental processes and human impacts, so the assessment of groundwater is not fully complete: "The dependence on groundwater and the pressure on groundwater is increasing. We still do not know enough about groundwater resources," warned Neno Kukuric, Director of the International Groundwater Resources Assessment Center (IGRAC-UNESCO), during his keynote speech at the 7th Latin America-Spain Water Dialogues. "Groundwater is invisible and that is why we must invest and dedicate more resources to share knowledge and information, as well as create greater synergies." 

World-renowned expert Dr John Cherry – the 2020 Stockholm Water Prize Laureate – has made important contributions to make groundwater visible, advancing groundwater knowledge and making it widely available for free through The Groundwater Project. SWM interviewed Dr John Cherry for the inaugural issue of Smart Water Magazine Bimonthly in 2020.

We must not forget either that 40% of the world's available water is transboundary water. Groundwater does not stop flowing across political borders, and enormous resources are stored in transboundary aquifers – there are currently 468 identified transboundary aquifers and aquifer systems. This shared water can not only be a source of numerous conflicts over water resources, but also demonstrates that conserving them is a shared responsibility that must be placed at the centre of today's water governance scenario.

Why should we conserve groundwater?

The Spanish Climate Change Office and other research centres predict that there will be a gradual reduction in water supplies throughout the 21st century and that groundwater resources may be affected by up to 18%. This is in addition to other issues such as groundwater overexploitation – the Asia-Pacific region has the lowest per capita water availability in the world and groundwater use in the region is expected to increase by 30% by 2050 – and pollution – in North America and Europe, nitrates and pesticides are a major threat to groundwater quality.

An international study led by the University of Victoria (Canada) and published in 2019 in Nature analysed declines in groundwater levels resulting from groundwater pumping and linked them to declines in streamflow globally. In that report, researchers warned that unsustainable groundwater pumping exceeds recharge from precipitation and rivers in 20% of basins, and that, by 2050, environmental flow limits will be reached for approximately 42 to 79% of watersheds in which groundwater is pumped worldwide.

Those figures are in line with the UN warning that about 20% of the world's aquifers are being overexploited and that not knowing how much might exist in some places is a real problem when managing groundwater, so it is necessary to "improve our exploration, monitoring and analysis of groundwater resources to protect and better manage them and help achieve the Sustainable Development Goals".

Within the Sustainable Development Goals (SDGs), groundwater plays a key role in the 2030 Agenda, especially in the achievement of SDG 6, Clean Water and Sanitation, and SDG 13, Climate Action, both because of its potential to buffer the effects of water scarcity and because of its vulnerability to overexploitation and the effects of climate change. But the importance of groundwater conservation goes further, as reflected in the UNU-INWEH report Groundwater and Sustainable Development Goals: Analysis Of Interlinkages, which analyses the interlinkages between groundwater and the various targets of the 17 SDGs: 53 targets (42%) have a primary interlinkage with groundwater.