- USGS webpage: Land subsidence
- Fact sheet: Measuring Land Subsidence from Space (USGS)
- Measuring subsidence: BMP 2 Best Management Practices for the Sustainable Management of Groundwater, Monitoring and Identification of Data Gaps (Department of Water Resources)
- Setting thresholds:BMP 6 Draft Sustainable Management Criteria (Department of Water Resources)
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.