Groundwater houses most of the planet’s freshwater reserves. They are key for agriculture since they are a source of irrigation water in many areas of the planet.
Groundwater is found in cracks in the ground, trapped in sand and rock, and more than two billion people depend on it for irrigation or drinking.
Groundwater contributes greatly to maintaining flows in water flows such as rivers, lakes… Its reduction implies that the water level of aquatic ecosystems is affected.
Rampant and unsustainable extraction of groundwater reserves crucial for food production will “critically impact” rivers, lakes and wetlands in half of the Earth’s drainage basins by mid-century, according to a recently published study in Nature.
The current extraction rate far exceeds the level of recharge of aquifers and groundwater in general. As the world population and crops increase, water consumption does so in the same way.
In this study, the research group studied the rate at which existing groundwater fed rivers, lakes and wetlands around the planet and how pumping for agriculture affected that process, known as stream flow.
20% of drainage basins have reached their tipping point
During this study, they discovered that in about 20 percent of drainage basins, the tipping point where abstraction exceeded stream flow had already been reached.
They also used climate change models to predict how stream flow will decline in the future and found that between 42 and 79 percent of the world’s groundwater sites will not be able to support aquatic ecosystems by 2050.
Inge de Graaf, chair of environmental hydrological systems at the University of Freiburg, Germany, said this could have a devastating impact.
“It’s pretty clear that if there’s no more water in your stream, your fish and plants will die.”
«About half of irrigated crops depend on groundwater»
Inge de Graaf
Currently, regions that rely heavily on groundwater for crop production, including Mexico and the Ganges and Indus basins, were already experiencing declining river and stream flows due to overexploitation.
As demand for groundwater increases, areas of Africa and southern Europe will also see severe water disruptions in the coming decades, this team predicted.
In August, the Intergovernmental Panel on Climate Change issued a major assessment on changing land uses to combat global warming, arguing for more sustainable water use in agriculture as the world’s population reaches 10. billion by 2050.
De Graaf said some farming techniques have shown promise in reducing groundwater use, such as in parts of Southeast Asia’s Mekong Delta, where coconut palms are replacing intensive rice fields in several pilot projects.
British researchers already warned this year that future generations face a groundwater “time bomb” as underground systems would take decades to replenish.
In Spain, the Doñana National Park and the Tablas de Daimiel National Park, two wetlands of international importance, are in danger from the overexploitation of groundwater through illegal wells that prevent the correct quantification of the inputs and outputs of water to these ecosystems. This makes it difficult to take measurements since not all the real water balance data is available.