For the last 10 years groundwater in northern Indian states, namely Punjab, Haryana and Rajasthan has decreased by more than 88 million acre-feet. With the help of NASA's GRACE, (Gravity Recovery and Climate Experiment) satellites scientists have measured tiny movement in the planet's gravitational field to determine the rate of groundwater change in India. The areas that have been marked red had sightly less mass due to a net loss of groundwater and hence those areas displayed a weaker gravitational pull on the satellites. The areas that are in blue had greater mass and a stronger gravitational pull due to a net gain. According to Matt Rodell and his team, the water is being pumped and consumed for several activities, but a lot of it is being used to irrigate water-hungry farms. "If measures are not taken to ensure sustainable groundwater usage, consequences for the 114 million residents of the region may include a collapse of agricultural output and severe shortages of potable water," Rodell, who is based at NASA’s Goddard Space Flight Center, said in a statement.

Groundwater comes from the natural percolation of precipitation and other surface waters down through Earth’s soil and rock. It does not respond to changes in weather like lakes or streams and rivers. When groundwater is pumped up it takes nearly months or maybe even years to get back to original level.

Rodell's team found that groundwater levels have been declining by an average of one meter every three years (one foot per year).

And that's bad news.

"We don’t know the absolute volume of water in the Northern Indian aquifers, but GRACE provides strong evidence that current rates of water extraction are not sustainable. The region has become dependent on irrigation to maximize agricultural productivity, so we could be looking at more than a water crisis," Rodell said in the statement.