Nasa satellites have weighed the water lost by the US State of California's heartland since 2003.
The Sacramento and San Joaquin River Basins which support the highly productive Central Valley have shed over 30 cubic km of water in that time.
The data comes from the Grace mission which detects changes in gravity caused by water as it cycles between the sea, the atmosphere and the land.
It illustrates the impact of a drought but also excessive irrigation use.
It is big issue because of California's importance to food production in the US.
Its Central Valley is one of the major agricultural regions in the world.
It grows more than 250 different crops, accounting for a little under a tenth of all the food produced in the US by value. But the Central Valley also accounts for about a sixth of all the irrigated land in the US, making the region the second most pumped aquifer in America.
http://news.bbc.co.uk/2/hi/science/nature/8414252.stmThat's 30 kilometers high, 30 kilometers long and wide.