Lecture16_2011r -...

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Unformatted text preview: http://www.siograddept.ucsd.edu/faculty/driscoll/ California Water Supply Surfing after storms-Pollutant-laden storm water runoff plumes are common coastal ocean features throughout the Southern California Bight following winter storms. In Santa Monica Bay, these plumes have been associated with high toxicity and water-borne pathogens. This ERS-1 synthetic aperture radar (SAR) image illustrates the spatial extent of one of these plumes in the bay. Wind direction and speed are indicated by the black arrow, `MDR' denotes Marina del Rey, and `LAX' denotes the airport. (From DiGiacomo, Paul M. Benjamin Holt, and Libe Washburn, Pollution Hazards off the Southern California Coast: Satellite and In-Situ Observations of Naturally Occurring Oil Seepage and Storm Water Runoff Plumes, AGU Ocean Sciences Meeting, Honolulu, Hawaii, February 2002. ) Under natural conditions, perhaps 80-100% of precipitation will filter into the subsurface, with only 0-20% surface runoff. In urban areas, this is reversed, with 90-100% surface runoff. This results in rivers rising faster after storms and peaking higher. Increases flood dangers. Artificial levees and channelization…prevent stream from changing course, which it naturally wants to do. Different regions of California clearly have different precipitation patterns. Different levels of precip, rain vs. snow…affects how water moves across the landscape. Point out North Coast, Sierras and Central Valley, Mojave (South Lahontan), Colorado River region… Note most of the Central Valley receives very little rainfall… Precipitation on left. Population on right. Where is the water falling vs. where the people are? California Hydrologic Regions These hydrologic regions share similar precipitation and runoff patterns. What do the boundaries coincide with? Lots more info on each of these regions at: http://rubicon.water.ca.gov/v2index.html Watershed: The term "watershed” (in American usage), or drainage basin, refers to a geographic area where water and sediment drain to a common outlet. Watersheds are those land areas bounded by topographic features on the landscape (ridge lines) that catch falling rain and snow which drains to creeks, rivers, lakes, estuaries, lagoons, marshes, the ocean, or groundwater basins. (From San Diego Watershed Network webpage) Water collected in a watershed naturally remains in that watershed due to topographic constraints. Watersheds vs. hydrologic regions. There can be several major (and non-interacting) watersheds within each hydrologic region. Drainage basins Regional Water Imports & Exports Local demand does not equal local (natural) supply in most highlypopulated parts of California. We have developed a complex, artificial system of water distribution. State Water Project •Redistribute water primarily from Feather River watershed to urban areas. •Control spring flooding. •70% of water to urban and industrial use •30% to agricultural use Feather River The Feather River system provides most of the water for the State Water Project. Oroville Dam (above) is the largest SWP reservoir. The dam is the tallest in the US (770 ft.) State Water Project •Redistribute water primarily from Feather River watershed to urban areas. •Control spring flooding. •70% of water to urban and industrial use •30% to agricultural use Largest consumer of energy in California! 1 Gallon of water weighs 8 lbs. Raised over 2000’!! Central Valley Project •Transport water south to irrigate drier Central Valley farmlands. •Control spring flooding •Diverts waters from: •Trinity River •Sacramento River •American River •Stanislaus River •San Joaquin River •85% of water for agricultural use North Coast Region •Highest precipitation (and runoff) in the state: many areas receive >100 in/yr (some almost 200 in/yr) •Some snow in Klamath Mts and Trinity Alps, but snowpack doesn’t dominate the system. •Summer fogs--in some coastal redwood forests, >30% of water reaching ground drips from trees. •97% of land forest/range http://wwwdwr.water.ca.gov/ Smith river has highest runoff of water per acre in the state. Also only major watershed free of dams. Up to 90% of water from Trinity River diverted into Sacramento Valley (resulted in declining salmon runs) North Coast water supply and uses “Environmental” uses includes in-stream flow needs to maintain the health of the river and a smaller amount for wetland wildlife refuges. This is primarily what the “Dedicated Natural Flow” is for. Trinity Dam Up to 90% of Trinity River discharge diverted out of its watershed into Sacramento Valley. Part of Central Valley Project. Humboldt County--Eel River Huge seasonal variation--Note logrithmic scale. Winter rains vs dry summer season. High stream flow in winter--Note flood of 64/65. Note winter storm flow 1000-10000 times higher than summer flow. Braided rivers--varying discharge. Eel River--1 yr Sediment loads turn rivers brown during intense storm periods. This is natural, but is exacerbated by logging and grazing practices. Mattole River--10 yrs Mattole River--1 yr Inyo The Owens River is in the South Lahontan region in the rain shadow of the Sierras. Note differences between North Coast region rivers--which are strongly influenced by winter and spring rains--and Owens River (for example). Owens River streamflow is dominated by snowmelt. In what month/season is the peak flow? (See also next slide) How does the magnitude of the flow vary throughout the season? How might the streamflow in this river change if global warming continues and the Sierras start to lose their snowpack? What about rivers draining the west slopes of the Sierras like the Merced and Tolumne? Peak in July -- snowpack ...
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