Evening star. [volume] (Washington, D.C.) 1854-1972, 1953-12-30
Wetter Years Predicted
For Colorado Busin
Tree Rings Indicate Long
Dry Cycle Is About Over
By Thomos R. Henry

Gnarled, twisted, two-thirds dead
desert trees from 1000 to $500 years
old are providing fairly complete his
tory of Western weather during most
Of their lifetimes. They indicate the
possibility that Southern California
and the whole Colorado Basin soon may
have wetter years.
This has just been reported to the
Office of Naval Research by DR.. Edmund
Schulman of the University of Arizona,
who has been carrying out his re-
searches under Navy grant.
The growth of a tree each year is
marked by ring in its wood. The
breadth of this ring depends chiefly on
the amount Of rainfall during the year.
This has been known for almost half a
century and 1t has been possible to con-
Struct tree-ring calendars for a few
hundred years Of the past. Such cal
endars have been useful to archeolo-
gists in dating ruins but have been diff
cult to interpret and have had q big
margin Of error. Now they have been
largely abandoned in favor of more re-
liable dating methods. They never
have furnished reliable weather records
over long periods.
Strict Requirements.
DR.. Schulman set out to find single
trees in the Rocky Mountain area which
had been alive for long periods, which
necessarily grew slowly. and the size
OF whose ring increment responded al
most entirely to climatic conditions
each year. Only few species filled this
requirement.
The trees selected were all conifers-
Douglas fir, ponderosa pine, pinyon
pine and timber pine. These were be-
lieved to have maximum age of about
500 years.
DR.. Schulman's search soon revealed,
however. that some had much longer
lives. He has found some of the first
three species whose rings show that
they are about 1000 years old, and a
few Timber pines close to 1900 years
old. They have been, he says, extremely
Slow-growing. They usually are found
on steep. rocky slopes. stunted in
height. often with gnarled and Spirally
twisted trunks. and with sparse foliage.
They are inconspicuouS and undesirable
as lumber. Hence they have been left
in cut-over areas.
The story they tell may have de-
cided implications for the present, DR..
Schulman says.
What appears to be the most pro-
nounced climatic fluctuation of the
past 1000 years, and quite likely for
the preceding millennium also" he says,
was the approximately 200-year oscil-
lation in the amount of tree growth
and the inferred rainfall in the Colo
RADIO River Basin during the 18th and
14th centuries. From AID. 1915 to 1899
seriously deficient rainfall seems to
have been the rule. About AID. 1900
wetter years seem to have set in and
for the following two or three decades
storminess may have been generally
greater than for any comparable period
in the modern gauge records for this
region Not until 1889 does there APP
pear to have been lasting return to
drier times for the basin as a whole.
More Wet Years.
THE statistical chance that the gen.
orally deficient rainfall and run-off
of recent decades in the Colorado Basin
is to continue for many decades more,
as in the 1200s, is small. Indeed one
might look more juStif1ably for an early
swing to excessive rainfall"
About the middle 18th century, he
says, the records show. there was a
change in the Colorado Basin towards
relatively short cycles of drought and
excessive rainfall. The opposite, how
ever, appears to have been the case
in the Missouri Basin. This pattern
has continued essentially to the present.
1t is about time for wetter period
along the whole course of the Colorado.
unless another longtime change in
pattern has set in, and there are no
such indications.
Still" DR.. Schulman points out"
until succession of wet years has oc-
Cured little uneaSiness is perhaps
warranted