Groundwater-Storage Reductions

Throughout the late 1800s and into the 1920s when two thirds of the Santa Clara Valley had been irrigated, water flowed freely from wells. Water-level declines of more than 200 ft occurred in the Santa Clara Valley from the early 1900's to the mid 1960's (Fowler, 1981). Land subsidence was first detected in 1933 (Poland and Ireland, 1988). As the decades passed, groundwater levels continued to...

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.

Land subsidence has been ongoing in the dry lake beds throughout the Mojave and Morongo groundwater basins since the 1960s. In a study conducted from 2004 - 2009, continuous GPS stations were added to interferometric synthetic aperture radar (InSAR) methods to measure changes in land surface altitude.

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.

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.