Land subsidence is the gradual settling of the Earth’s surface. Subsidence can be caused by a variety of factors; however, here in California the primary causes are groundwater pumping and the decomposition of wetland soils after conversion to farmland. Groundwater extractions that deplete or “drain” confined aquifer systems can cause the sediments to compact and the land surface to sink (or subside).
Extensive groundwater withdrawals from aquifer systems have caused land subsidence in many California basins. Land subsidence can damage structures such as wells, buildings, and highways.
land subsidence tool
The land subsidence mapping tool from USGS illustrates areas of both historical and current land subsidence across California.
Coming soon, the Groundwater Exchange will pull documents from the California Water Library. In the meantime, you can view those documents by clicking here.