Humans have pumped so much water out of the ground that the Earth has tilted on its axis by 80 centimetres to the east in less than two decades, scientists have found.
The groundwater pumping has been so furious that an estimated 2,150 billion tonnes were sucked up from beneath the Earth’s surface between 1993 and 2010 alone, according to a study in the journal Geophysical Research Letters.
The water has mostly been used for drinking, irrigation and livestock – in India and the US in particular – as the rapidly growing world population and climate change sent demand soaring.
Climate change has massively pushed up water demand by changing rainfall patterns, making supplies less reliable – while rising temperatures have increased the number of droughts and the need for irrigation more generally.
What is groundwater?
Groundwater is fresh water that is stored in the ground. Most rainfall soaks into the ground, where it’s filtered down through the soil and into the rocks, in a process called infiltration.
Groundwater can be found almost everywhere underground, from near the surface to depths of 30,000ft. It is stored in aquifers, which are permeable formations that contain fine holes or cracks that allow water to flow.
It is an important natural resource that can be used for:
- River flows, even during dry periods
- Ecological diversity in rivers, lakes, and wetlands
- Public water supplies
- Industry and agriculture
How has water pumping made the Earth’s axis tilt?
This water eventually finds its way back into the oceans as it evaporates from the land, returns to the Earth as rainfall and runs off into rivers and on into the sea.
As a result, there has been a massive relocation of water on the planet – most of all from northwestern India and western North America – which has be redistributed to oceans around the world.
And this is what has tilted it on its axis at a rate of about 1.7 inches (4.3 centimetres) a year, giving a total of 78.5 centimetres, during the 18-year study period.
While spinning on its axis, Earth wobbles like an off-kilter top. The distribution of water on the planet affects how mass is distributed.
Like adding a tiny bit of weight to a spinning top, the Earth spins a little differently as water is moved around, wobbling and shifting its spin axis.
What does this mean for the planet?
Experts say changes due to groundwater pumping, while dramatic in their own way, don’t run the risk of shifting seasons, or length of the day – except perhaps by a tiny fraction of a second every few years.
Of much greater significance, for life on Earth, however, is that the redistribution of water pushed up the global sea level by 0.24 inches in the 18 years to 2010.
While this is not a huge rise, scientists say the rate of water distribution has accelerated significantly in recent decades and expect the trend to continue, as climate change and rising populations push demand for water ever higher.
This means the sea level could rise at an increasingly rapid pace.
Furthermore, with melting ice from climate change already pushing up sea levels considerably, every inch of sea level rise counts – for low-lying communities in particular.
