The worst subsidence has already increased the risk of flooding in the sparsely populated region, including to the low-lying town of Dos Palos, population 5,400, said Christopher White, manager of the Central California Irrigation District.
That's because portions of the area's flood control system have sunk, reducing their ability to contain floodwater. Local flood officials are crafting emergency plans for where to place sandbags when big rains return.
"We've got some serious issues," said Reggie Hill, manager of the Lower San Joaquin Levee District, which maintains part of the flood canal.
Other canals and dams that deliver water to irrigate the fields of hundreds of growers are also losing capacity as parts of them sink.
White oversees the local effort to respond to the subsidence. His irrigation district, which serves 1,900 growers, spent $5 million in recent years to raise canals and dams.
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.