WSP00380

• File Number: 8149.100
• Description: Miscellaneous Small Projects-Project Studies - NRCS-Ft Lyon Canal Co-Limestone-Graveyard Creeks
• State: CO
• Basin: Arkansas
• Water Division: 2
• Date: 9/1/1992
• Author: US Dept of Agricultu
• Title: Lower Arkansas River Basin - Water Quality Study - Colorado
• Water Supply Pro - Doc Type: Report/Study

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002536

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II. DESCRIPTION OF THE AREA

A. Location

The Lower Arkansas River Basin Water Quality study in
Colorado includes approximately 290,000 acres of irrigated
cropland along the Arkansas River between the Pueblo
Reservoir and the Colorado-Kansas state line. The irrigated
cropland is located below the main irrigation canals,
generally within a few miles on either side of the river,
for approximately 160 miles. Parts of five counties
(Pueblo, Crowley, otero, Bent, and Prowers) are included in
the study area.

The total land area of the Arkansas River Basin is 27
percent of the entire state of Colorado and has
approximately 20 percent of the population. within the
study area, Pueblo is the major urban area with a population
of 98,629 people. other incorporated places in the study
area include: Fowler (1,154), Rocky Ford (4,162), La Junta
(7,637), Las Animas (2,481), Lamar (8,343), and Holly (877).

The elevation of the study area varies from approximately
4,700 feet at the Pueblo Reservoir to about 3,400 feet above
sea level at the state line. The land is nearly level to
gently rolling. The river has an average gradient of nine
feet per mile as it flows to the state line. There are
numerous tributaries to the Arkansas River. Some of the
plains streams, such as the Purgatoire, Apishapa, and
Huerfano Rivers, have created canyons in the middle and
upper reaches. Stream channel aggredation occurs where they
confluence with the Arkansas River.

The mean annual precipitation for Pueblo is approximately 12
inches per year. The annual precipitation slowly increases
from here in the study area to the state line where the
annual precipitation is about 15 inches. There is a high
degree of annual and seasonal variabilityy More than 80
percent of the annual precipitation falls from April to
September.

B. Geology

Geology of the Lower Arkansas River Basin Water Quality
Study Area lies in the Great Plains province and includes
portions of the Colorado Piedmont and High Plains sections.
The Colorado piedmont section is composed largely of
cretaceous shale, chalk, limestone, and sandstone.