Images

Hypothetical model grid showing A, types of cascading hydrologic response units and B, land-surface altitudes and cascading flow directions.

USGS hydrographer measuring streamflow using a handheld Acoustic Doppler Velocimeter in fast moving floodwater Cajon Creek near Keenbrook, California. 

USGS technician measuring streamflow in the Sisquoc River near Garey, California, upstream of the Santa Maria Mesa Road Bridge.

 USGS Streamgaging equipment and cableway on the Pit River near Canby, California operates year round.

Turbid waters in the Little Holland Tract area of the Sacramento-San Joaquin Bay Delta, California. Turbidity affects light penetration and  ecological productivity, recreational values, and habitat quality, and causes lakes to fill in faster.

A USGS hydrologic technician takes streamflow measurements during flooding of the Sisquoc River, a tributary of the Santa Maria River, near the town of Garey in Santa Barbara County. 

National Geodetic Survey vertical control bench mark H1235 RESET in Merced County, California. H 1235 RESET is in the median of State Highway 15. This is one of several bench mark locations used to help measure the largest recent subsidence in the area using repeat surveys.

National Geodetic Survey vertical control bench mark W990 CADWR in Merced County, California. W 990 CADWR is on the Mariposa Bypass Bridge on Washington Rd. This is one of several bench mark locations used to help measure the largest recent subsidence in the area using repeat surveys.

Invasive water primrose (Ludwigia species) and water hyacinth (Eichhornia crassipes) line the marsh edge in Mandeville Cut near the Port of Stockton, California’s third largest port.  Invasive aquatic vegetation – dominated by Brazilian waterweed, water hyacinth, and water primrose – has increased exponentially in recent years, cloggi

Invasive aquatic vegetation chokes Lindsey Slough, creating a potentially challenging environment for fish and other aquatic life. The slough is the site of a 2014 restoration project in the Sacramento-San Joaquin Delta to improve freshwater tidal marsh and spawning habitat for Delta smelt and other fish.

Landscape ecologist Shruti Khanna uses a threshing rake to collect Brazilian waterweed (Egeria densa) in the Delta. The USGS is conducting research to measure the impact of invasive aquatic vegetation on sediment transport, turbidity, and marsh accretion rates in Delta. 

USGS and USBR workers discuss important issues.

SF Bay-Delta from the point of view of a USGS research vessel, taken at sunset. 

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

SF Bay-Delta shoreline showing vegetation and hills in the background.

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.