Images

USGS and USBR workers discuss important issues.

Land subsidence contours showing vertical changes in land surface in the central San Joaquin Valley area, California, during January 8, 2008-January 13, 2010. The top graph illustrates elevation changes computed from repeat geodetic surveys along Highway 152 for 1972-2004.

Map showing estimated regions of subsidence derived from interferograms for 2008–2010 and selected surface-water conveyance infrastructure in the San Joaquin Valley area of the Central Valley, California.

Two USGS Hydrologists taking water sample

The 2014 King Fire burned 97,717 acres in the El Dorado National Forest and on private timberlands. The fires in these burn areas reduce the forest canopy, exposing snowpack to direct sunlight. This increases the rate of snowmelt and evaporation, impacting runoff and groundwater replenishment.

In a field in northern California, seen here is a sunflower with several bees. Bees are drawn to sunflowers for several compelling reasons, and understanding this attraction sheds light on both the nature of bees and the characteristics of sunflowers.

USGS researchers collect water samples from the Research Vessel Dorah Henry to measure suspended sediment concentration in Central San Francisco Bay. Samples were collected using a D-96 sampler that collects samples over the entire depth of the water column allowing for a  depth-integrated sample.

Reduced surface-water availability (associated with droughts) during 1976-77, 1986-92, 2007-09, and 2012-current caused groundwater-pumping increases, water-level declines to near or beyond historic lows, and renewed aquifer compaction.

Dr. Judith Drexler, taking core sample at Six Gill Slough, Puget Sound, Washington

Microcystis is one of the most common bloom-forming cyanobacteria, AKA, blue-green algae.  Many strains of this species produce a family of potent liver toxins, the microcystins.

A groundwater well that is outfitted with equipment to collect samples to test for several water quality parameters.

Scientists from the USGS meet with members of the Hinkley Technical Advisory Group. In this photo USGS researchers demonstrate an X-Ray fluorescence meter. (Image courtesy of Project Navigator.)

USGS hydrologist, Carmen Burton, collects a groundwater sample from a well in Hinkley, CA. The samples are being collected as part of a study analysing the occurrance of hexavalent chromium in groundwater. 

The dominant cause of land subsidence in the Sacramento-San Joaquin Delta is decomposition of organic carbon in the peat soils. Under natural waterlogged conditions, the soil was anaerobic (oxygen-poor), and organic carbon accumulated faster than it could decompose. Drainage of peat soils for agriculture led to aerobic (oxygen-rich) conditions.

Reduced surface-water availability (associated with droughts) during 1976-77, 1986-92, 2007-09, and 2012-2016 caused groundwater-pumping increases, water-level declines to near or beyond historic lows, and renewed aquifer compaction.

Pre-subsidence diagram showing the relation between surface and subsurface processes with linkage to land subsidence. The linkages to subsidence deformation are briefly summarized for surface-water, landscape and groundwater flow processes.

Detailed location map of the Cuyama Valley, California watershed and groundwater basin, with the hydrologic model boundary and major rivers.

Post-subsidence diagram showing the relation between surface and subsurface processes with linkage to land subsidence. The linkages to subsidence deformation are briefly summarized for surface-water, landscape and groundwater flow processes.

Withdrawal estimates for each category represent the total amount of water removed from the water source, regardless of how much of that total is consumptively used. In most cases, some fraction of the total withdrawal will be returned to the same or a different water source after use and is available for other withdrawals.

Extremely low water levels at Huntington Lake, CA in August, 2014 during the severe drought California faced from 2012 -2016.  Located in the Sierra Nevada mountain range, Huntington Lake is a reservoir operated by the U.S. Bureau of Reclamation.

Extensometers are used in land subsidence studies to measure the compaction and expansion of the aquifer system to some depth. This pipe borehole dual-stage extensometer was built in 2008 in San Lorenzo, CA and measures compaction from 10 to about 300 meters. The illustration highlights the features that can be seen in the photograph.