WSP11116

• File Number: 8056
• Description: Drought Preparedness
• State: CO
• Basin: Statewide
• Date: 2/1/1976
• Author: Dept of Water Resour
• Title: Special Report on Dry Year Impacts in California
• Water Supply Pro - Doc Type: Report/Study

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Drainage from the soil to streams and use by plants
this fall has reduced soil moisture to such an extent that
several inches of precipitation will be required in most
areas of the State before appreciable streamflow would occur.

Historical Perspective

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Both the economy of the State and water storage and
distribution facilities have changed so much in the last 25 years
that many of the effects experienced in earlier dry years ~an
no longer be expected, but some useful comparisons are possible.
At this time in 1975, a dry year, although not nearly as severe
as the present season, seemed likely. However, heavy precipita-
tion beginning early in February and continuing well into May
turned a comparatively dry year into a good water year.

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Serious or potentially serious dry years have occurred
frequently in California, notably 1918-19, 1919-20, and 1923-24
in the more distant past and in recent history 1946-47, 1947-48,
and 1962-63. The dry period 1928-34 had a great impact on the State
with 6 dry years in a row, even though anyone of the years alone
would not have caused serious problems. This series of dry years
motivated action on the part of water users and managers to im-
prove the reliability of their water supplies so that such prob-
lems would not occur again.

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The driest year of record in most parts of California
was 1923-24. It was one of the few years that was drier on
February 1 for most parts of the State than is the case this
year. However, from Bakersfield south, 1975-76 has been even
drier. Figure 3 presents comparisons of precipitation at selected
stations in California with some dry years in the past;

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Dry farm crops and rangeland suffered severely in
1923-24, and much irrigated agriculture also experienced sub-
stantial water deficiencies. The drought led to formation
of the Rivers Problems Committee in the San Joaquin Valley, and
the appointment of a water supervisor to closely watch for
wasteful practices and to stop waste. Ground water was the main
source of supply at that time since the reservoirs in the
sierras which we know today were not in existence.

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At that time many districts depended on streams with
little or no regulatory storage except nature's snowpack reser-
voir. Streamflow Nas very low and many streams and springs
that ordinarily flow year round became dry. Figure 4 presents
snow accumulation by area for this year compared with some
historic dry years. Table 1 also compares reservoir storage
for 1975-76 and for 2 prior dry years.

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