During the recent droughts of 2007-2010 and 2012-2017, groundwater pumping has increased from the combined effects of the drought and land-use changes, re-initiating land subsidence. In order to document historical subsidence and monitor continued changes, the USGS has gathered and interpreted data from a variety of sources.
In California, land subsidence—mostly from groundwater pumping—was first documented by the USGS in the early 20th century. Completion of State and Federal water projects that bring water from California's wet north to its dry south allowed some groundwater aquifers to recover, and subsidence decreased in these areas. Subsidence continues today, sometimes at high rates of more than 1 foot/year.