Groundwater levels are falling in many places around the world, and this decline has accelerated recently. In some places, the rate reaches half a meter annually, according to a new study published in the scientific journal nature.
The researchers included 170,000 wells in their analysis. These wells form part of 1,673 groundwater systems in more than forty countries. Of these systems, 36% show a decline of at least ten centimeters per year, and 12% even a decline of half a meter or more.
In 30 percent of the areas studied, the decline in groundwater levels has accelerated since 2000. This was particularly the case in areas with dry climates where water is used for irrigation. In coastal areas, this poses a risk of salty seawater entering groundwater. Agricultural production may also be at risk elsewhere.
Extraction is unprofitable
“It's very worrying,” says Mark Perkins, a hydrologist at Utrecht University who was not involved in the study. “If you look at Iran and Mexico, but also at California and the high mountains in the United States, you see that the groundwater level will soon become so low that it will no longer be economically viable for agriculture to extract it.”
The question, he says, is how to postpone that moment for as long as possible. “The decline is often stronger in areas where food safety depends on groundwater levels. This relationship is a real concern when it comes to food safety in the future.”
Sometimes also increased
On the other hand, groundwater levels have risen again in several places. In 6 percent the level rose by 10 centimeters per year, and in 1 percent even by 0.5 meters or more. This is mainly due to policy measures.
In the Thai capital, Bangkok, levels rose after new rules imposed restrictions on water pumping, and in Albuquerque, America, surface water was successfully added to groundwater. The researchers hope that measures will be taken in more places to reduce groundwater consumption and replenish groundwater.
Perkins describes the research as “real hard work. Based on local measurements, it shows the global situation of groundwater in areas where depletion is occurring.” As the number of measurement points increases, part of the work is being automated, and he sees this as a point of interest: “In India, for example, some of the measurement points are located next to irrigation canals. So you don't actually know exactly what you are measuring.”
Scientists, including Perkins, had previously modeled the decline in groundwater levels. It has also already been measured using satellites. “But measurements on the ground provide information we did not have before. In southern India, for example, the decline appears to be greater than expected. The acceleration of the decline in groundwater levels since 2000 was also not clear from previous studies. We only have satellite data Industrial since 2003, so we were not able to make this comparison.”
Neder water fall
The problem of low groundwater levels occurs mainly in Africa, Asia and Central America, but this does not mean that the Netherlands is protected. “Until the summer of 2018, I thought this did not apply to the Netherlands. But because of the drought, so much water has been extracted from the ground that we can no longer catch up with it in 2019. It will not be a structural problem for us.” “For us, but it could certainly become a problem over several years.”
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