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

WATER RESOURCES OF CALIFORNIA 497
RUNOFF
Estimated mean seasonal natural runoff of the Lahontan Area for
the 53-year period from 1894-95 to 1946-47 is 3,177,000 acre-feet, or 4.5
percent of total surface runoff of the State. Minimum seasonal runoff
amounting to 930,000 acre-feet occurred in 1923-24, and the maximum,
totalling 7,070,000 acre-feet, in 1906-07. Water supply during each year
of the 10-year period from 1923-24 to 1932-33, except 1926-27, was less
than the 53-year seasonal mean, and the average was only 63 percent of
this long-time mean.
Snow falls on large portions of the tributary drainage of the Lahontan
Area. Consequently, a substantial portion of seasonal runoff is delayed
until late spring and early summer. For Truckee River, a typical
Lahontan Area stream that flows from the Sierra Nevada, snow melt
contributes 95 percent of seasonal runoff. Minimum runoff in the Area
occurs from August to October, inclusive. On Truckee River runoff
during these months is only 4.9 percent of the seasonal total.
Stream gaging stations in the Lahontan Area, are listed in Table 71
together with the average, maximum and minimum seasonal runoff for
stations with more than 10 years of record. Longest available records of
stream flow are for Truckee River at or near the state line, and for Owens
River near Round Valley. The record for the 'rruckee has been maintained
since September, 1899, and that for Owens River since August,
1903, except from October, 1923, to March, 1927. Records for these two
stations are no longer published by the Geological Survey, but may be
secured from the Federal Court Watermaster for Truckee River and
from the Department of Water and Power of the City of Los Angeles
for Owens River.
Estimated mean seasonal natural runoff of the 53 years from 1894-95
to 1946-47, shown in Table 72, has been prepared i:r{ the same manner
as corresponding tables in preceding chapters. For stations with partial
records, mean seasonal runoff shown is the mean of estimated natural
flow for each season of the 53-year period. At locations where records are
not available, only directly derived long-time mean estimates are given.
Estimates of seasonal natural runoff of main stream and tributary
basins having records, presented in Table 73, were made in accordance
with principles outlined in Chapter III. Estimates of runoff from drainage
basins where records were not available were made by comparison
with runoff from other basins. In deriving the 53-year seasonal mean for
unmeasured streams discharging into lakes in the northern portion of
the Area, inflow to a lake, computed from records of lake levels, was taken
to be runoff of the stream during the period of record. A relationship
was then established with an adjacent stream, and the missing record
was estimated by the third method of restoring missing records described
in Chapter III.
Estimates of mean seasonal runoff for streams or basins for which
no records of any type existed were made by comparison with runoff of
adjacent areas, on the basis of geographical, geological and meteorological
conditions. The portion of mean seasonal runoff that was estimated for
the Lahontan Area approximates 1,183,000 acre-feet, the remaining
1,994,000 acre-feet being based on records.
An unusual feature of the natural flow estimate for Truckee River,
in Table 73, is the occurrence in several years of negative values in esti-