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If you stand almost anywhere in the world, water is moving along the ground beneath your feet. Groundwater provides drinking water for approximately half of the world’s population
If you stand almost anywhere in the world, water is moving along the ground beneath your feet. Groundwater provides drinking water for approximately half of the world’s population and almost half of the water used to irrigate plants. It supports rivers, lakes and marshes during droughts. Groundwater is a renewable resource, but some aquifers can take decades or even centuries to recover after depletion. The current understanding of this problem is based mainly on where and how often people record water level measurements in wells.
In a newly published study, our team of data scientists, water experts, and policy experts collected the first global dataset on these levels. We analyzed millions of groundwater level measurements from 170,000 wells in more than 40 countries and mapped how groundwater levels change over time.
Our study has two main results. First, we show that rapid groundwater depletion is common worldwide and that rates of decline have accelerated in recent years, with levels dropping by 20 inches or more per year in some places.
Second, our research also found many cases where intentional actions stopped groundwater depletion. These results show that societies are not doomed to inevitably deplete groundwater reserves, and that this important resource can be regained with timely intervention.
Many factors determine groundwater levels, including geology, climate and land use. But groundwater levels sinking deeper and deeper in a given place often indicate that humans are pumping it out faster than nature can restore it.
Some of the 300 million measurements we collected were recorded with automatic measuring devices. Others were created in this area by people from all over the world. And these measurements paint a disturbing picture.
These show that since 2000, water levels have fallen in many more places than they have risen. In many places, especially in arid regions with intensive agriculture and irrigation, the water table is dropping more than 20 inches (0.5 meters) per year. Examples include Afghanistan, Chile, China, India, Iran, Mexico, Morocco, Saudi Arabia, Spain, and the American Southwest.
Our second and more worrying finding is that the rate of groundwater decline is increasing in approximately one-third of the areas where we collected measurements. Rapid depletion of groundwater is common in dry climates where large areas of land are used for agriculture. This suggests a potential link between groundwater-fed irrigation and increased groundwater depletion.
A rapid and rapid decline in the groundwater level has many harmful consequences. When groundwater levels drop, drinking water supplies from wells and springs may become depleted. People and communities that depend on these wells may lose access to what may be their only source of affordable drinking water.
For example, it is installing wells that provide fresh water to homes in California’s San Joaquin Valley, where groundwater depletion has accelerated since the early 2000s. This problem is likely to persist and worsen unless steps are taken to stabilize groundwater resources. Dry wells can also threaten crop production. Groundwater depletion has long been considered one of the greatest threats to global irrigated agriculture; Wells provide almost half of the water used for irrigation worldwide.
In areas where groundwater normally flows into rivers, a drop in groundwater level can alter this flow and cause rivers to flow underground. This affects the ecology of the river and reduces downstream water supplies. In the United States, leaky streams are more common where groundwater withdrawals are high; This underscores how pumping groundwater can directly reduce the amount of water flowing underground into nearby rivers.
Land subsidence away from the coast can damage infrastructure. This poses a critical problem in areas with low water levels, such as Tehran and Mexico City. In most cases the main cause is excessive groundwater pumping. Finally, falling water tables can push seawater deeper into the ground and contaminate coastal groundwater systems, a process known as seawater intrusion. When seawater intrudes, coastal aquifers can become too salty to be used as drinking water without energy-intensive desalination.
We also found places where the groundwater level has improved. Strategies that communities use to replenish groundwater resources include developing new alternative water sources, such as local rivers; adoption of a policy to reduce demand for groundwater; and intentional recharge of aquifers with surface water.
In Eldorado, Arkansas, the water table dropped nearly 200 feet (60 meters) between 1940 and 2000 as local industry pumped water from the aquifer.
In 1999, a new policy created a water fee structure that gave businesses incentives to seek new water sources. By 2005, a pipeline was built to transfer water from the Ouachita River to El Dorado. This new source has reduced the demand for groundwater, and groundwater levels in the region have increased since 2005.
Between 1980 and 2000, so many private wells were drilled in Bangkok for domestic, industrial or commercial purposes that groundwater withdrawals doubled and groundwater levels fell. Authorities responded by quadrupling groundwater extraction fees between 2000 and 2006. Total groundwater withdrawal decreased and levels began to improve as users found other water sources.
In a valley near Tucson, Arizona, the water table dropped 100 feet as irrigation withdrawals increased after the 1940s. Leaky ponds were constructed to help restore depleted groundwater.
These ponds are filled with water from the Colorado River, which flows hundreds of kilometers into the region through canals. When these ponds are drained, they recharge the depleted aquifer. Due to these leaky reservoirs, the groundwater level in the valley has risen by approximately 60 meters in places.
Our analysis shows how important it is to monitor groundwater levels in many places. As groundwater levels decline in many places, communities and businesses that depend on them need accurate information about their water resources so they can take timely action to protect them.
Source: Port Altele
As an experienced journalist and author, Mary has been reporting on the latest news and trends for over 5 years. With a passion for uncovering the stories behind the headlines, Mary has earned a reputation as a trusted voice in the world of journalism. Her writing style is insightful, engaging and thought-provoking, as she takes a deep dive into the most pressing issues of our time.
