BOARD01033

• Board Meeting Date: 11/13/1963
• Description: Minutes
• Board Meetings - Doc Type: Meeting

I

has asked me to read a 'preliminary Estimate of
Water Use by Phreatophytes on Selected Portions
of the Rio Grande. Conejos, and San Antonio
Rivers' which was submitted by Mr. Bittinger
and Mr. Enix of the Agricultural Engineering
Department of Colorado State University under
date of November 9th. It says:

'This report covers an estimate of water
use by vegetation along selected reaches of the
Rio Grande, Conejos, and San Antonio Rivers in
Rio Grande, Alamosa and Conejos Counties of
Colorado. The work was carried out at the
request of the San Luis Valley Water Conser-
vancy District and the Conejos Water Conser-
vancy District.

Aerial photographs of the areas under
study were inspected at the USDA Agricultural
Stabilization and Conservation offices. Trac-
ings were made showing vegetative areas along
the rivers and an estimate of vegetative density
was made from the photographs. Density was
estimated in three classes: dense, medium and
light. The area in each class was determined
by planimeter measurements from the tracings.

The Rio Grande River was studied over the
reach beginning 9~ river miles above the city
of Del Norte and terminating at the Colorado-
New Mexico state line. The Conejos River was
studied from approximately one river mile above
Mogote to its confluence with the Rio Grande.
The San Antonio was studied over a distance of
7~ river miles above its confluence with the
Conejos.

I

The estimates of water use are based on
the Blaney-Criddle method outlined in USDA
publication August 1950. According to this
authority the water use by native vegetation
in the areas of this study are: Dense, 23.7
acre inches per acre; Medium, 19.8; Light,
15.8. These data are for the growing season
only, but will be adequate for the estimates
of annual water use in this area.