River San Joaquin

Two major rivers in California influenced by a Mediterranean climate are the Sacramento River and the San Joaquin River. The Sacramento River drains 72,132 km with a relief of 4,317 m. Mean discharge is 650 m /s with peak flows in the winter and early spring and with minimum flows in the late summer and early fall. The San Joaquin River drains 83,409 km with a relief of 4,418 m. Mean discharge is 130 m /s with peak flows in spring and low flows in late summer and fall. Population density is 24 people/km in the Sacramento River basin and 29 people/km in the San Joaquin basin. Agriculture in the Central Valley of California that encompasses parts of both basins is the primary user of water in both basins [1]. 

Fig. 1 Map of the Delta in central California, USA with the California state map inset to show location within the state. The Delta is formed at the confluence of the Sacramento River and the San Joaquin River. Export of water from the Delta occurs mainly from the State Water Project pumping plant and the Central Valley Project pumping plant in the south Delta...

The water supply to the Delta comes predominantly from the Sacramento River ( 80%) with lesser amounts from the San Joaquin River ( 15%) and rivers on the east side of the Delta ( 5%). Year-to-year variability in water supply is large. Combined average annual unimpaired runoff (an estimate of flows without upstream dams or diversions) for the Sacramento and San Joaquin rivers for the past century ranges from 6.2 km in 1977 to 68 km in 1983 [2]. The percentage of freshwater flows that go to San Francisco Bay are estimated to be 87% in wet years, 69% in average years, and 51% in dry years. Climate variability associated with the Mediterranean chmate of the region is an essential component of the Delta ecosystem. 

Water quality issues for the lower Sacramento and San Joaquin rivers and for the Delta include salinity, dissolved organic carbon (DOC), suspended sediment. 

Another contaminant of concern for the Delta is Se. Selenium occurs in high concentrations in the soils of the western San Joaquin Valley associated with salts that have accumulated in this region [10]. Selenium is recycled through agricultural retom flows to the river and transported to the Delta and San Francisco Bay. The Se is transformed into a more bioavailable form by microbial communities and aquatic plants. The Se is passed through the foodweb with particular concern for bottomfeeding migratory waterfowl and predatory fishes. The hydrodynamics of water from the San Joaquin River is an important consideration in the intensity and distribution of Se contamination within the Delta. 

Quinn NWT, Jacobs KC, Chen CW, Stringfellow WT (2005) Elements of a decision support system for real time management of dissolved oxygen In the San Joaquin River Deep Ship Channel. Environ Modell Softw 20 1495-1504... 

Menconi, M. and A. Paul. 1994. Hazard Assessment of the Insecticide Chlorpyrifos to Aquatic Organisms in the Sacramento-San Joaquin River System. Calif. Dept. Fish Game, Environ. Serv. Div., Admin. Rep. 94-1. 74 pp. 

Prest, H.F., W.M. Jarman, S.A. Bums, T. Weismuller, M. Martin, and J.N. Huckins. 1992. Passive water sampling via semipermeable membrane devices (SPMDs) in concert with bivalves in the Sacramento/San Joaquin river delta. Chemosphere 25 1811-1823. 

Muscle, Wisconsin California San Joaquin River September-November 1986 whole fish 0 FW 1... 

Johns, C. and S.N. Luoma. 1990. Arsenic in benthic bivalves of San Francisco Bay and the Sacramento/San Joaquin River delta. Sci. Total Environ. 97/98 673-684. 

Saiki, M.K., M.R. Jennings, and W.G. Brumbaugh. 1993. Boron, molybdenum, and selenium in aquatic food chains from the lower San Joaquin River and its tributaries, California. Arch. Environ. Contam. Toxicol. 24 307-319. 

San Joaquin River whole 1984-85 5 species 1986 5 species 1986-87 7 species whole Sacramento River San Francisco Bay San Joaquin River... 

Striped bass, Morone saxatilis California whole juveniles San Joaquin River ... 

California San Joaquin River 1987 maximum concentrations recorded Water 0.025 FW 122... 

Bacey J, Spurlock F, Stamer K, Feng H, Hsu J, White J, Tran DM (2005) Residues and toxicity of esfenvalerate and permethrin in water and sediments, in tributaries of the Scaramento and San Joaquin Rivers, California, USA. Bull Environ Contam Toxicol 74 864-871... 

Less than 10% of the sediment samples taken from the San Joaquin River and its tributaries in California (an area of heavy organochloride pesticide use) in 1985 contained mirex residues all samples contained less than 0.1 pg/kg (ppb) (Gilliom and Clifton 1990). 

Gillion RJ, Clifton DG. 1990. Organochlorine pesticide residues in bed sediments of the San Joaquin River, California. Water Resources Bulletin 26 11-24. 

Bluegill, Lepomis macrochirus, San Joaquin River, CA, whole fish, 1981, total chlordanes Striped bass, Morone saxatilis, San Francisco Bay, CA, Max. 14 FW Max. 759 LW 17... 

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