Groundwater Levels
Groundwater Levels
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Spirit Leveling
Elevation or elevation-change measurements are fundamental to monitoring land subsidence, and have been measured by using interferometric synthetic aperture radar (InSAR), continuous GPS (CGPS) measurements, campaign global positioning system (GPS) surveying, and spirit-leveling surveying. The most precise measurements tend to be made using spirit-leveling surveys and extensometers. Spirit...
Land Subsidence in the Santa Clara Valley
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...
Mojave Land-Subsidence Studies
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.
Land Subsidence in the Coachella Valley
Groundwater is an important water-supply source in the Coachella Valley. The demand for water has exceeded the deliveries of imported surface water, and groundwater levels have been declining as a result of increased pumping. A network of GPS stations has been set up in the valley to monitor subsidence resulting from declining groundwater levels.
Delta-Mendota Canal: Evaluation of Groundwater Conditions and Land Subsidence
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...
Land Subsidence Along the California Aqueduct
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.
Piezometers and Groundwater Levels
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.
Aquifer Compaction due to Groundwater Pumping
Although land subsidence caused by groundwater pumping has caused many negative effects on human civil works for centuries, especially in the highly developed urban or industrialized areas of Europe, the relation between subsidence and groundwater pumpage was not understood or recognized for a long time. Recognition began in 1928 when pioneer researcher O.E. Meinzer of the U.S. Geological Survey...
Land Subsidence in the San Joaquin Valley
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.