Central Valley

Extensometers measure the compaction and expansion of the aquifer system, providing depth-specific data that can help CAWSC scientists better understand the rate, extent, and at what depths in the system subsidence is occurring.

A numerical modeling approach was used to quantify groundwater conditions and land subsidence spatially along the Delta-Mendota Canal. In addition, selected management alternatives for controlling land subsidence were evaluated.

In areas adjacent to the Delta-Mendota Canal (DMC), extensive groundwater withdrawal from the San Joaquin Valley aquifer system has caused areas of the ground to sink as much as 10 feet, a process known as land subsidence. This could result in serious operational and structural issues for the Delta-Mendota Canal (DMC). In response, the USGS is studying and providing information on groundwater...

Subsidence is a global problem and, in the United States, more than 17,000 square miles in 45 States, an area roughly the size of New Hampshire and Vermont combined, have been directly affected by subsidence. More than 80 percent of the identified subsidence in the United States is a consequence of human impact on subsurface water.

Measurements of elevations, aquifer-system compaction, and water levels are used to improve our understanding of the processes responsible for land-surface elevation changes. Elevation or elevation-change measurements are fundamental to monitoring land subsidence.

The California Water Science Center has been involved in multiple studies simulating land subsidence associated with groundwater withdrawal. The simulations can be used to estimate the magnitude, location, and timing of subsidence. They can also be used to evaluate management strategies to mitigate adverse effects from subsidence while also optimizing water availability.

The San Joaquin Valley is one of the most productive agricultural regions in the nation. Beginning around the 1920's, farmers relied upon groundwater for water supply. Over time, overpumping caused groundwater-level declines and associated aquifer-system compaction and land subsidence that resulted in permanent aquifer-system storage loss.