Images

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.

Uroplatus henkeli, Leaf Tailed Gecko Group. Female

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. 

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.

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.

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.

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

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.

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.

Standard configuration of a Sacramento-San Joaquin Delta flow and water quality monitoring station.  The U.S. Geological Survey (USGS) has operated and maintained a monitoring network in the Sacramento-San Joaquin Delta since the 1970’s.

Juvenile sand lance (Ammodytes hexapterus) (top) and surf smelt (Hypomesus pretiosus) (bottom) collected on Bainbridge Island, Washington. Scale is in inches.

The extensive withdrawal of groundwater from the unconsolidated deposits of the San Joaquin Valley has caused widespread land subsidence—locally exceeding 8.5 meters (m) between 1926 and 1970 (Poland and others, 1975; fig. 2), and reaching 9 m by 1981 (Ireland, 1986).

Generalized surface geology of the Anza–Terwilliger study area, Riverside and San Diego Counties, California (modified from
Rogers, 1965).