Some areas of the San Joaquin Valley are subsiding at the fastest rates ever measured, according to a hydrologist and lead author of the report.
The bulk of the sinking 1,200-square-mile area in central California is dropping about an inch per year. But one 2-square-mile area studied is subsiding almost a foot.
The worst subsidence increases flooding risks as portions of the area’s flood control system have sunk, reducing their ability to contain floodwater. Local officials are creating emergency plans for where to place sandbags when big rains return.
Other canals and dams that deliver water to irrigate the fields of hundreds of growers are also losing capacity as parts of them sink.
The federal Delta-Mendota Canal, which delivers water from northern California to growers and cities in the Central Valley, runs near the edge of the subsidence bowl and was the focus of the USGS study.