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<br />THE SACRAMENTO SAN JOAQUIN SYSTEM
<br />
<br />The flood management system in the Central Valley
<br />includes 23 res8IVoirs with flood detention space and
<br />more than 1,760 miles at federally designated project
<br />levees, overflow weirs, bypass channels and chan-
<br />nel enlargements. This system extends from Ord
<br />Ferry on the Sacramento River near Chico to the
<br />southern tip of Sherman Island in the Delta, and from
<br />Gravelly Ford west of Fresno to Stockton on the San
<br />Joaquin River. The system also contains an almost
<br />equal length of non-project (local) levees, which are
<br />mostly maintained by reclamation districts. Recla-
<br />mation districts are created when landowners form
<br />a local agency in accordance with state law and as-
<br />sess themselves for flood control, reclamation pur-
<br />poses and water supply,
<br />
<br />A unit of the state's Department at Water Resources
<br />(DWR), the Division of Flood Management, inspects
<br />and evaluates the maintenance of all the project
<br />levees and channels. Most project levees are main-
<br />tained by local agencies, such as reclamation and
<br />levee districts. Where local interests are unable to
<br />perform satisfactory maintenance, DWR may take
<br />over the maintenance of the project levees and
<br />assess landowners for the costs. DWR also is
<br />responsible for channel maintenance of the
<br />Sacramento River Flood Control Project. Local
<br />agencies maintain the San Joaquin River system.
<br />
<br />The levee and bypass system along the Sacramento
<br />River system carries a maximum of 600,000 cubic
<br />feet per second (ets), many times the normal flow of
<br />the Sacramento River. Only a sixth of that flow -
<br />110,000 cfs - is carried in the river itself. Nearly
<br />500,000 cfs is channeled into the Yolo Bypass, a
<br />huge floodway, which is 3 miles wide in some parts.
<br />
<br />In addition to the levee system, a series of dams for
<br />flood control and water supply was built on the
<br />western slopes of the Sierra Nevada, These dams
<br />include Shasta Dam on the Sacramento River near
<br />Redding, Oroville Dam on the Feather River near
<br />Oroville, New Bullards Bar Dam on the Yuba River
<br />near Marysville, and Folsom Dam on the American
<br />River, 20 miles east of Sacramento. Dams have
<br />substantially reduced peak flows on many of northern
<br />California's major rivers by temporarily holding back
<br />high flood flows,
<br />
<br />The 250.mile long San Joaquin Valley is comprised
<br />of two basins: the northern basin drained by the
<br />San Joaquin River and the southern Tulare Basin.
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<br />The southern basin, now a closed basin, has four
<br />tributaries, the Kings, Kern, Tule and Kaweah rivers.
<br />These rivers once created Tulare Lake but because
<br />of irrigation diversions and the 1928-1934 drought
<br />no longer flow into the lake,
<br />
<br />The San Joaquin River has a series of major flood
<br />control and water supply dams along the western
<br />slope of the southern Sierra Nevada, These include
<br />Friant Dam on the San
<br />Joaquin River, New
<br />Exchequer Dam on the
<br />Merced River, Don
<br />Pedro Dam on the
<br />Tuolumne River, New
<br />Melones Dam on the
<br />Stanislaus River and
<br />Camanche Reservoir on
<br />the Mokelumne River,
<br />Friant Dam and its res-
<br />ervoir, Millerton Lake,
<br />located in the foothills of
<br />the Sierra Nevada
<br />northeast of Fresno,
<br />provide flood control for
<br />the San Joaquin River basin, The lake has a total
<br />capacity of about 520,000 acre-feet, with 170,000
<br />acre-feet seasonally reserved for flood control.
<br />
<br />The San Joaquin River system is designed to
<br />channel snow melt and not high rain-fed flows,
<br />It also is only about 10 percent the size of the Sac-
<br />ramento River. Concern over the river system's ability
<br />to convey flood flows to the Delta without levee
<br />failures became reality during the 1997 New Year's
<br />floods. Unprecedented inflows from the subtropical
<br />storms into Friant Dam on the San Joaquin River
<br />almost caused the dam to be overtopped, The high
<br />inflows into Friant, as well as into Don Pedro Dam
<br />from the Tuolumne River, caused flood managers to
<br />release flows several times the rivers' carrying
<br />capacity, causing multiple levee breaks downstream
<br />of the dams,
<br />
<br />Proposals are being studied to improve flood capac.
<br />ity on the San Joaquin River. They include modify-
<br />ing the operation of designated flood storage space;
<br />providing additional flood storage by directing peak
<br />overilows onto wildlife refuge lands; raising Friant
<br />Dam; and modifying the floodway to reduce water
<br />levels during high flows to maintain environmental
<br />diversity in the floodway and reduce erosion.
<br />
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<br />A ('ombination (~lIe\'ees,
<br />dams, storage reselToirs,
<br />b.\jHJSs challnels alld
<br />(}\'Clj10\\' n'eirs protect
<br />Central Valley Ih'es and
<br />property from seasonal
<br />j7om/illg.
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