WSP01146

• File Number: 8281.400
• Description: Colorado River Studies and Investigations -- Colorado River Depletion Projections
• Basin: Colorado Mainstem
• Water Division: 5
• Date: 1/1/1959
• Title: Depletions in Flow of Colorado River at Lee Ferry Due to Man's Activity in Colorado River Basin in Colorado
• Water Supply Pro - Doc Type: Report/Study

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11lpine cov~r. was unabsorbed.

Mr..c. L. Forsling. formerly with the soil conservation service. has
made the fOllowing comments on .the general effects of vegetal cover
on runoff:

"Forest cover and other vegetation serves to regulate and control
watel' where it fclus. It is evident that land use practices have
greatly reduced the regulating characteristics of the vegetal cover..

"The veliletal cover breaks the impact of rainfall. It intercepts pr',!-
cipitation, 'it cijsperseasoilmoisture by transpiration, it binds soil
against. erosion and it . holds moistllre by the blotter effect of a covel' .
of undecomposed or partially decomposed material. All these factOrs .1
help disperse preci.pitation and thus d.ecrease runoff.

"Of greater influence in this respect is the effect of the Plant covel' ~d
more :especially the organic material at or near the surface in the ab-
sorption of water by the soil. The cover increases the infiltration ca-
pacitylU;ld water-holding capacity of the soil. It fllters the watel' before
entering the: soil and then helps to maintain .clear passageways for water
in the soil. It keeps water spread out over the surface andhindel'lJ sur-
faca now, thus giving the soil more of a chance to absorb water; it n';;
tards erosion and thus prevents the formation of gullies which would
iDor~se runoff.

''The effects of vegetal cover on runoff are attested by actual cases
which show that as much as 88% of the precipitation woUld rim (ill a
denuded area as compared to 11 a% from a forested area. "

Mr. Sherman M. Woodward, chief water control planning engineer for
T. V.A. says: "Activity of man increased the runoff of the Tennessee
River between 1867 IU;ld 1937 some 11%".

It is estimated that the runoff from the graaing lands might have in-
creased Z5% over what it was in a state of natllre when almost the
entire area was covered with dense growth of grass.

ESTIMATED INCREASED RUNOFF DllE TO DEPLETION
OF GRAZING LAND

The acreage in the Upper Colorado River Basin has been separated
as to. uee in a report, "The Colorado Rivdl'by the U. S. a. R., as
shown in the following table:

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