Artwork: huxley.media via DALL-E 3
Climate change on the planet is affecting literally every aspect of our lives. Global warming is affecting groundwater levels in particular. It would be hard to exaggerate the role that groundwater aquifers play in modern civilization. We drink water every day, we irrigate our fields with it. It is essential for global food security and maintaining stable communities and ecosystems. So, what is happening to groundwater sources today?
GLOBAL GROUNDWATER MONITORING
Groundwater is a climate buffer of sorts because it supports communities and ecosystems that are vulnerable to water availability. But as human-induced climate change accelerates, they are becoming vulnerable.
Human activities deplete groundwater by affecting rainfall and using 70% of groundwater for irrigation. Does humanity have a sustainable water future, or are we facing critical depletion of groundwater sources? A global study of groundwater provides the answer to these questions, the data on which is published by Nature.
Scientists have summarized measurements and observations of 170,000 wells installed in 1,693 aquifer systems in 40 countries around the world. This unprecedented scale of monitoring has been continuously conducted over the past 40 years and covers about 75% of global groundwater withdrawal.
This leads the authors of the study to believe that the data reflect actual groundwater level trends and help determine whether groundwater levels are declining, stabilizing, or rising and at what rate.
CAN GROUNDWATER LEVELS BE CONTROLLED?
Scientists found a decrease in 21st century levels worldwide compared to 1980–2000 levels. But they also noted that the decline has slowed and, in some places, even reversed. In the 21st century, levels rose steadily in nearly 50% of the aquifer systems that were available for monitoring. Reductions have slowed in 20% of systems, reversed in 16%, and 13%, levels have risen steadily.
These positive changes occur for a host of different reasons. Among them are those that humans have had a hand in. For example, in the eastern Saq aquifer in Saudi Arabia, the reason for slowing down groundwater depletion was government policy aimed at limiting water demand. Rising groundwater levels in the Bangkok watershed appear to be due to government decisions that have significantly tightened regulation of its use.
Tucson, Arizona, has also begun implementing a set of measures aimed at recharging aquifers. As a result, the prospects for systems with depleting reserves have improved significantly. The situation has also improved in the Abbas-e Sharghi basin in Iran, which was recharged by pumping water from other basins in the region.
DROUGHT AND INSTABILITY OF WATER HORIZONS
All these cases show that, with the will and desire, the state of groundwater sources can be managed, and people can give the green light to the restoration of natural resources. However, overall, recovery on the planet is relatively slow. While the average rate of recovery is 5 cm per year, the rate of reduction is 20 cm. The reason is the changing climate, due to which the state of groundwater becomes unstable even in regions where there are positive trends.
In 30% of water horizons, the rate of level reduction increases. This is especially rapid in cultivated drylands, where people are increasing water extraction for irrigation from groundwater sources to compensate for declining precipitation.
This is particularly the case in California, northern India and Pakistan, and Iran’s West Qazvin Plain. Groundwater use seems to be dominated by a relatively small number of countries. However, the problem may go far beyond the areas analyzed.
POPULATION GROWING, SPRINGS DEPLETING
Groundwater source monitoring, although covering an unprecedented number of countries, is unfortunately far from reaching all of them. Notable gaps include central China, much of Southeast Asia and Latin America, and almost all of Africa. These regions of the world are now experiencing rapid population growth, which means their dependence on groundwater is likely to increase.
Water will be needed both to meet basic human needs and for further economic development. In order to have a more objective picture of the entire planet, monitoring needs to include these areas as well, and include parameters such as water quality. This is very important for global security, as about half of the world’s population uses groundwater for drinking.
PREPARE FOR WATER SCARCITY
Increasing water scarcity in the subsurface and deteriorating water quality could turn into a real catastrophe for the whole of humanity. That is why it is crucial to constantly monitor trends, and they are different in different parts of the planet: in some regions, the decline in groundwater levels is accelerating, while in others, the level is stabilizing or even increasing.
Today, the world is preparing for a temperature rise of at least 1.5 °C and subsequent changes in drought and precipitation patterns. Improved groundwater monitoring methods will allow a better assessment of groundwater as a climate buffer and sustainable water resource.
These data are a warning signal to mankind to prepare for future climate change impacts and to develop and implement measures to stop the accelerating depletion of groundwater.
Original article: Groundwater decline is global but not universal