East Oregonian : E.O. (Pendleton, OR) 1888-current, 1905-08-15
INFLUENCE OF FORESTS ON
STREAM SYSTEMS.

There has been n great deal of dis
cussion about the effect of the re-
moval of forests upon the flow OF
streams in the vicinity, There cannot
be any doubt that the rise and dis
charge of these are more gradual
where forests are retained than when
they have been cut away. 1t has been
observed. however, that brooks and
rivers show eccentricities even In To-
calities where there never was any for
est.
To some extent these may be--in-
deed, they probably are-due to the
variability of rainfall. In no one
spot is the total annual precipitation
the same. There are years of extra
abundance and years of scarcity. But,
aside from this, there can be no doubt
| that still another influence is at work.
f. w. Hanna, one of the engineers
of the United States geological survey,
who is stationed in Chicago, declares,
in Engineering News, that the rivers
of Southern Wisconsin, Southern Min
nesota and Northern Missouri have
suffered in respect to evenness of flow
since the prairies of that region have
either been converted into pastures OF
come under cultivation. be-
He thinks that the thick covering OF
prairie grass that once overlaid the
soil served to retard the run off
from the surface. somewhat as
sponge, and, hence, promoted even
ness Of flow. Now. he says, the gras!
is grazed off smoothly and the grounC
is packed so hard under the hoofs q
cattle that the flow is much free
, and more sudden than formerly. TIT
tendency is to promote alternate eN
tremes of high ard low level in tn
neighboring streams. t.t
In Mr.. Hanna's opinion, fully one
: twentieth of the entire prairie are'
was once wet marsh land. Tracts
this sort existed around the heads o
small streams, the drainage beini
l through "sloughs" when there wa
e heavy precipitation. Dense vegeta
$ ton. often several feet high, was foun
there. and around and in 1t there wa
usually an accumulation of water 10
- several days after every heavy ram
= storm. What has occurred since tina
era may be gathered from these re
marks of the writer
The majority of these natural resel
yoirs have been drained by sma
bitches that have grown into compai
= atively enormous proportions Dot
n laterally and vertically. These ditcht
n have cut down through the peaty sol
thus reducing the ground water leVe
and the once impossible slough
: now either cultivated or pastured.
e If the area of these "sloughs al
,s proximated one-twentieth OF the trli
"a utary area of a river having dramas
area of 1000 square miles there wou
- he in this basin so square miles
"slough" reservoirs. Now, If 1t Is a
d sumed that the water. after a heaN
rain. stood OIL feet deep over this are
"A above the ground proper, and that
took five days to escape from II
! slough, there would be 32S teet p'
rs second added to the flow of the riv'
er during this period.
n Thus it appears that the cohsta
rur off would be increased somethir
p" over O.3 fet per second over ea'
Suuare mile Tor an ulluou"hS -
le period of 35 days. Periods OF drou
of such length are very rare in u
section under discussion, and cons
ouently. the computed increme
should be considerably more thah {
timated. Evidently any increase
~ y, constant run off approximating
". " feet per square mile would greatly a
~ feet the maximum and minimum flc
H. of a river.
-. The data upon which the foregoil
-, arguments are based have been q
a. rived from years of experience a.
= observation on the prairies and fro
an intimate acquaintance with t
"a rivers flowing through them.
,,t viously estimates based on them m
contain large per cent OF err
10 However, the writer is certain tn
al I,ley contain enough truth to fu
~ demonstrate the theory that guilty
-, ton. and especially pasturage n
Irainage. are the cause nf accentu'
ho ell r,aximum and minimum sire
os flow in the humid prairie states.