Bulletin 1.pdf - California Department of Water Resources - State of ...

308 WATER RESOURCES OF CALIFORNIA
Sierra Nevada, and Cottonwood, Stony, Cache, and Putah Creeks which
drain the coastal ranges west of the Sacramento Valley. San Joaquin
River flows into the Sacramento from the south and its principal tributaries,
the Cosumnes, Mokelumne, Calaveras, Stanislaus, Tuolumne, and
Merced Rivers, are all from the Sierra Nevada. Kings, Kaweah, Tule, and
Kern Rivers also drain from the Sierra Nevada but into Tulare Lake,
rather than northward into San Joaquin River. A portion of the flood
flow of Kings River is tributary to San Joaquin River, by way of Fresno
Slough, and in times past during periods of flood Tulare Lake has overflowed
into San Joaquin River. No large streams enter San Joaquin
Valley from the coastal ranges. Areas of drainage basins in the Central
Valley Area are listed in Table 53.
PRECIPITATION
It is difficult to generalize regarding precipitation of the Central
Valley Area in terms of "light," "moderate," or"heavy." Storms
sweeping in from the ocean over the coastal ranges and across the Central
Valley are influenced by changes in elevation. As elevation is gained on
the west slope of the coastal ranges precipitation increases. Inversely, it
diminishes down the east slope. In general, little variation is registered
as storms pass eastward across the Central Valley floor, but as they
ascend the west slope of the Sierra Nevada precipitation again increases,
reaching the maximum as the crest is approached. Then, as storms pass
over the crest and down the east side, it again decreases.
Heavy snowfall is a winter feature of the Sierra Nevada at elevations
above about 3,000 feet in the northern portions and above about
4,000 feet in the south. Its depths are exceeded in few parts of the United
States. In March, 1907, and again in 1911, 308 inches of snow was measured
at Donner Summit. During the seasons of 1880 and 1890, as estimated
from records of marks at stations on the transcontinental railroad
crossing the Sierra Nevada, the fall was 370 inches. These figures are
given for snow depths at time of measurement. Accretions during a season
have exceeded 800 inches at Tamarack, at an elevation of 8,000 feet
in Alpine County. The Cascade Range on the Olympic Peninsula in
WashingtQn is the only area in the United States to record greater
depths. Snow in measurable quantities on floors of the Sacramento and
San Joaquin Valleys is rare.
Two hundred and ninety-nine precipitation stations with records of
10 years or more are being maintained in the Central Valley Area. They
are listed in Table 54, together with mean, maximum and minimum seasonal
precipitation. These stations are at elevations ranging from sea level
to 8,000 feet. The longest record is for the station at Sacramento, which is
unbroken since 1849. Precipitation stations in the Central Valley Area
with continuous recorders are listed in Table 55. Stations with records of
less than ten years are listed in Table 56.
Precipitation in the Area decreases progressively from north to
south. Mean seasonal rainfall on the floor of Sacramento Valley between
the Sacramento-San Joaquin Delta and Red Bluff varies in general from
15 inches to 25 inches. On the San Joaquin Valley floor, which is bounded
by a seasonal isohyet of 15 inches, minimum seasonal precipitation of
less than five inches may occur in the Tulare Lake and Buena Vista Lake
sections. A minimum seasonal total of 0.57 inch was recorded at Rio