Explained: Excessive Groundwater Extraction Leading To Fall In Water Levels & Why It's Not Good

According to the National Aeronautics and Space Administration (NASA) of the United States, groundwater in the northern part of India has reduced by 88 million acre-feet over the last couple of years.

Unsustainably high groundwater use as well as its decline lead to water scarcity for coming generations, however, it is not confined to that. Scientists are working hard to figure out how the decrease in groundwater is compacting the land above, having caused irreversible shifts in the aquifers. This could make cities even more vulnerable to flooding and water logging.

Shutterstock/Representational Image

What is land subsidence?

Land subsidence is defined as the progressive or abrupt sinking of the earth's surface caused by the elimination or dislocation of subsurface earth components. The main causes are aquifer-system compression caused by extensive underground water withdrawals, drainage of organic soils, basement mining of mineral deposits, oil and gas, and natural compaction or collapse caused by boreholes or thawing permafrost, and seismic activity.

BCCL/Representational image

Land subsidence is increasingly causing damage each year, according to a paper published in Nature Scientific Papers titled 'Tracking hidden crisis in India's capital from space: implications of unsustainable groundwater use.' Over 80% of global land subsidence is caused by extreme underground water extraction, which raises intergranular strain and induces soil particle reorganisation, actually resulting in aquifer compression and ultimate land subsidence.

Groundwater extraction levels in India continue rising in order to accommodate the increasing nation's drinking water, agro-based, and industrial necessities. The Delhi National Capital Region (NCR) is among the fastest-growing urban areas in the world, with as many as 6,25,000 households lacking access to water sources. For their everyday water needs, people depend on underground water or private vessels.

BCCL/Representational Image

The effects of groundwater on the land above

Underground water remains deep beneath the land crust, where it fills the spaces left by pore spaces or rock fractures. Water is pressed at such depths, pushing the earth upward. "Both the water and the substance beneath share the load of the earth," Shagun Garg, a civil engineer and researcher at the University of Cambridge, told Mongabay. "Whenever the groundwater is excessively extracted, the substance beneath becomes the only entity for handling the weight," he added.

India is ranked first in the world for its elevated use of groundwater. Even inside India, the northern Gangetic valleys are more heavily exploited than other regions. The disappearance of aquifers is hastening changes in the structure of the earth's surface.

BCCL/Representational image

Alluvial groundwater research in the Delhi NCR area discovered that the ground has started to sink and continues to sink at a significant pace. During 2014-2016, specific sections of Delhi, such as Kapashera near the Indira Gandhi International airport, experienced a land subsidence speed of 11 cm annually, which further increased to 17 cm each year during two following years.

BCCL/Representational Image

What happens when land sinks?

Sinking ground can imply a variety of things. According to the study, if land sinking is expanded out over a large area, this could imply that the region will become flood-prone. However, if the pace of sinking varies, it could have an effect on civil facilities such as roads, buildings, and residences. It may cause fundamentals to deteriorate or cracks to form in buildings.

To evaluate the true effects of land subsidence at a specific location, computational data must be combined with a comprehensive ground assessment. Nonetheless, it is estimated that by 2040, land subsidence will affect approximately 8% of the world's top layer and approximately 1.2 billion people living in 21% of the world's big towns.

BCCL/Representational image

Land subsidence, along with many other natural disasters, is expected to have a greater impact on Asia than on the rest of the world. With 86 percent of Asians vulnerable to the impacts of land subsidence, approximately US$8.17 trillion is arguably at stake.

Can we repair the land that has sunk due to subsidence?

Groundwater refill is a natural method. People can lessen land subsidence if underground water refill is equal to the volume exploited, or if we use water in a sustainable manner.

However, research indicates that aquifers are so heavily exploited in the region that the rate of regeneration far outweighs the consumption rate. According to reports, India's groundwater are in critical condition, with a yearly use of approximately 433 billion cubic meters of underground water.

Watch this vide explainer:

For more on explainers, news and current affairs from around the world, please visit Indiatimes News.