Estimates of suspended sediment entering San Francisco Bay from the Sacramento and San Joaquin Delta, San Francisco Bay, California

• Published in: Journal of hydrology (Amsterdam) Vol. 323; no. 1; pp. 335 - 352
• Main Authors: McKee, Lester J., Ganju, Neil K., Schoellhamer, David H.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 30-05-2006; Elsevier Science
• Subjects: Brackish; deltas; Earth sciences; Earth, ocean, space; estuaries; Exact sciences and technology; Freshwater; Hydrology; Hydrology. Hydrogeology; Interannual; Load; Long term; Management implications; Marine and continental quaternary; pollution load; rivers; sediment yield; sediments; Surficial geology; Suspended sediment; suspended sediment concentration; Tide; water erosion; watershed hydrology; California; San Joaquin River; San Francisco Bay; Northeast Pacific; United States; North Pacific; USA, California, San Francisco Bay; INE, USA, California, San Francisco Bay; USA, California, San Joaquin R; USA, California, San Joaquin Delta; USA, California, Sacramento; Suspended sediment; Tide; Load; Management implications; Long term; Interannual; stream transport; floods; models; concentration; North America; tides; remobilization; drainage basins; interpolation; suspended materials; islands; deltaic sedimentation; discharge; erosion; Pacific Ocean; deltas; sediment volume; landform evolution
• ISSN: 0022-1694; 1879-2707
• DOI: 10.1016/j.jhydrol.2005.09.006

This study demonstrates the use of suspended-sediment concentration (SSC) data collected at Mallard Island as a means of determining suspended-sediment load entering San Francisco Bay from the Sacramento and San Joaquin River watersheds. Optical backscatter (OBS) data were collected every 15
min during water years (WYs) 1995–2003 and converted to SSC. Daily fluvial advective sediment load was estimated by combining estimated Delta outflow with daily averaged SSC. On days when no data were available, SSC was estimated using linear interpolation. A model was developed to estimate the landward dispersive load using velocity and SSC data collected during WYs 1994 and 1996. The advective and dispersive loads were summed to estimate the total load.
Annual suspended-sediment load at Mallard Island averaged 1.2±0.4
Mt (million metric tonnes). Given that the average water discharge for the 1995–2003 period was greater than the long -term average discharge, it seems likely that the average suspended-sediment load may be less than 1.2±0.4
Mt. Average landward dispersive load was 0.24
Mt/yr, 20% of the total. On average during the wet season, 88% of the annual suspended-sediment load was discharged through the Delta and 43% occurred during the wettest 30-day period. The January 1997 flood transported 1.2
Mt of suspended sediment or about 11% of the total 9-year load (10.9
Mt).
Previous estimates of sediment load at Mallard Island are about a factor of 3 greater because they lacked data downstream from riverine gages and sediment load has decreased. Decreasing suspended-sediment loads may increase erosion in the Bay, help to cause remobilization of buried contaminants, and reduce the supply of sediment for restoration projects.