WSP08775

• File Number: 8056
• Description: Drought Preparedness
• State: CO
• Basin: Statewide
• Date: 1/1/1979
• Author: USGS
• Title: Hydrologic and Human aspects of the 1976-77 Drought
• Water Supply Pro - Doc Type: Report/Study

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CHRONOLOGY OF THE 1976-77 DROUGHT

71

1976-77 reversed the trend because the
increased use of ground water to meet the
demands for water initiated another period of
pumping overdraft and the resumption of
subsidence (Lofgren, 1977).
Subsidence causes significant changes in
storage characteristics of an aquifer system
during the first cycle of water-level decline,
Pore water is squeezed from the water-bearing
deposits, and permanent compaction occurs in
the fine-grained beds. Therefore, the pore
space available for storage is reduced, and
pumping rates that occurred in 1977 will lower
the water levels much faster, possibly 10 to 20
times faster, than the same rate of pumping
would have caused during the first cycle that
ended in the late 1960's,

Hydroelectric Power Generation

Hydroelectric power generated in northern
and central California is an integrated opera-
tion of 105 hydroelectric plants. Virtually
every plant was adversely affected by the
drought of 1976-77. Only a few plants were
actually shut down for lack of water, but at
other plants the hours of operation were
reduced and the capability of the generators at
variable head plants decreased because of low
heads, The significant result was that hydro-
electric generation in 1977 was 10 billion
kilowatt-hours; whereas, the average output is
24 billion kilowatt-hours. The deficit of 14
billion kilowatt-hours was directly related to
the drought, and the replacement of most of
the deficit by purchases from other electric
utilities and additional use of steam generating
plants increased production costs to one utility
by $326 million (E, F, Kaprielian, written
commun.,1978).
The major hydroelectric development in
the southern Central Valley is in the upper San
Joaquin River basin, Hydroelectric power
generation by this project averages 3.5 billion
kilowatt-hours; but in the 1976 water year,
output was only 2.5 billion kilowatt-hours and
in 1977 it dropped to 1.1 billion kilowatt-hours.
The snow and rain that fell on the watersheds
in 1976 was not enough to produce the 2,5
billion kilowatt-hours; therefore, heavy de-
mands were made on water in storage which
was not replaced during the winter of 1976-77
when precipitation was very low. The system
still met peak demands for short periods only

because special operating schedules were
developed by careful planning. The cost to
replace the 2-year deficit of 3.4 billion
kilowatt-hours was $85 million,
Hydroelectric power generation at several
small plants on streams without storage is
usually reduced when the snowmelt runoff
ceases. In both 1976 and 1977 power genera-
tion had to be curtailed earlier than usual,

Forests

The drought conditions caused the fire
season to start early, The larger fires of the
13,300 fires that occurred in California in 1976
were in June and July. Forest fires usually
burn about 25 percent of the amount burned
annually by July 15; but 85 percent of the
194,000 acres burned in 1976 had been burned
by then. In September 1977, the California
Department of Forestry estimated damage to
timber and watersheds by recent fires at $250
million. About 1,850 fires occUrred in Califor-
nia in August 1977, burning in excess of
410,000 acres, and the 11,900 fires in 1977
burned 449,000 acres.
The loss of trees because of the two-year
drought was tremendous, About six million
trees that could be used for commercial
timber died from drought-induced afflictions,
This loss has been estimated to be between 2.5
and 3,8 billion board feet of marketable
lumber.
The fire that started in the hills near Santa
Barbara, Calif. spread into areas with expen-
sive homes and caused millions of dollars of
damage.

Activities Resulting from the Drought

The Director of the California Department
of Water Resources (Robie, 1978) reported
that more than 100 communities in California
adopted some form of mandatory rationing
during 1977. Allowances were as low as 50
gal/d per person. Statewide urban consump-
tion was 20 percent less than that in 1976, but
communities on the Monterey Peninsula and in
the Marin Municipal Water District reduced
water use by 49 and 53 percent, respectively,
during the first 9 months of 1977 compared to
the same period in 1976, The reduction in
water use in 1977 was slightly more than
400,000 acre-ft which exceeds the projected