The Ongoing Collapse of the World's Aquifers When humans over-exploit underground water supplies, the ground collapses like a huge empty water bottle. It's called subsidence, and it could affect 1.6 billion people by 2040.  The city of Jakarta is sinking as much as 10 inches a year. Such land subsidence could affect a fifth of the world's population in the next two decades.PHOTOGRAPH: ED WRAY/GETTY IMAGES AS CALIFORNIA’S ECONOMY skyrocketed during the 20th century, its land headed in the opposite direction. A booming agricultural industry in the state’s San Joaquin Valley, combined with punishing droughts, led to the over-extraction of water from aquifers. Like huge, empty water bottles, the aquifers crumpled, a phenomenon geologists call subsidence. By 1970, the land had sunk as much as 28 feet in the valley, with less-than-ideal consequences for the humans and infrastructure above the aquifers. >"When humans over-exploit underground water supplies, the ground collapses like a huge empty water bottle. It's called subsidence, and it could affect 1.6 billion people by 2040."