The sinking of the ground's surface -- or'subsidence' -- will threaten nearly a fifth of the world's population come the year 2040, a study has warned. An international team of researchers led from Spain have created a new model that estimates local subsidence risks across the globe. Subsidence is usually caused by the removal of local groundwater -- and can be triggered by dry spells, the roots of trees and shrubs and human activities. Experts warn that increasing droughts in the future will see subsidence occur more often -- and, as the global population grows, with greater impact on civilisation. Land subsidence typically hits hardest in regions with a high population density, greater demand for groundwater extraction and areas undergoing water stress.
As an engineering problem, subsidence damages infrastructure, causes roads to crack and give rise to sinkholes – expensive problems to fix, said Lohman. 'One of the places where it really matters in California is the aqueduct system that brings water to the region. 'They're engineered very carefully to have the correct slope to carry a given amount of water,' she said. 'Now, one of the major aqueducts in that area is bowed and can't deliver as much water. It's been a huge engineering nightmare.' 'Eventually, the water quality and cost of extracting it could get to the point where it is effectively no longer available.' Funding for this research was provided by NASA.
The world's coastal residents are experiencing more extreme sea level rise than is widely appreciated because they are concentrated in places where the land is sinking rapidly, a study published Monday in Nature Climate Change has found. Sea levels are rising globally as Earth's ice sheets melt and as warming sea water expands. But on a local scale, subsidence, or sinking land, can dramatically aggravate the problem. Cities like New Orleans and Jakarta are experiencing very rapid sea level rise relative to their coastlines--the land itself is sinking as the water is rising. Now, an international team of researchers has demonstrated that this one-two punch is more than a local problem.
The land under Beijing is sinking by as much as four inches per year because of the overconsumption of groundwater, according to research published in the journal Remote Sensing this month. The rate of sinking threatens "the safety of the public and urban infrastructure," the study says. This is because uneven sinking could damage trains, buildings and other structures. Experts from China, Spain and Germany worked together to analyze data from satellite imaging and global positioning sensors and tracked changes in the ground level from 2003 to 2011. Their findings were first drafted earlier this year and revealed that the city's Chaoyang district, home to Beijing's growing Central Business District, is sinking fastest, at a rate of more than four inches per year.
Since the 1920s, excessive pumping of groundwater at thousands of wells has caused land to subside, or sink, by as much as 8.5 meters (28 feet) in sections of California's San Joaquin Valley. This subsidence is exacerbated during droughts, when farmers rely heavily on groundwater to sustain one of the most productive agricultural regions in the United States. Subsidence is a serious and challenging concern for California's water managers, putting state and federal aqueducts, levees, bridges and roads at risk of damage. Total subsidence in California's San Joaquin Valley between May 7, 2015 and Sept. 10, 2016, as measured by ESA's Sentinel-1A and processed at JPL. Two large subsidence bowls are evident, centered on Corcoran and southeast of El Nido, with a small, new feature between them, near Tranquility.