WSP05425

• File Number: 8101
• Description: Arkansas River Basin Description
• State: CO
• Basin: Arkansas
• Water Division: 2
• Date: 9/1/1962
• Author: High Plains SCD
• Title: Watershed Work Plan - Limon Watershed Protection Project - Elbert and Lincoln Counties - Colorado
• Water Supply Pro - Doc Type: Report/Study

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Detailed investigations, including further explorations with
a p01;er drill, will be made at all sites prior to final design and
construction. Laboratory tests will be made on samples of foundation
materials, as well as on any materials to be used in the embankment
of the dams.

3edimentation Investigations

Ho previous records of sediment production were available
for the area included in the Limon \'Iatershed. Sedimentation
rates at the proposed reservoir sites were based on a reconnaissance
of the watershed area above these sites, as well as on the results
of a reservoir sediment survey made in 1955 on the Ferguson Reservoir
in the Big :3andy Creek Vlatershed.

The Ferguson Reservoir is located on Willow Gulch about 12
miles west of Limon. The drainage area above the reservoir is about
28 square miles and consists primarily of rangeland in comparable
condition to that in the Limon Hatershed. This reservoir had been
in operation for about 30 years at the time the emergency spillway
washed out in 1938. The rate of sediment cleposi tion in the reservoir
over this 30-year period was computed to be 0,12 acre-foot annually
per square mile of drainage area.

"

From a reconnaissance of the Limon \,atershed, it was concluded
that sediment production in the watershed is generally low. There
are no critical sediment source areas. Sheet erosion was estimated
to be the main source of sediment with minor mnounts being contributed
by gully and streambank erosion. Most of the area has a good grass
cover, and streambanks and beds generally are well protected by a
vegetative cover. There arealso several stock ponds on each of
the three mair. tributaries, These ponds tend to capture some of the
sediment "hich otherwise would be delivered to the f loodwater-
'. retarding reservoir sites.

In computing future rates of sedimentation at the proposed
reservoir sites, consideration was given to the a~mount of reduction
in secliment production that "ill result from proposed landrreatment
measures to be installed in the watershed, It is estimated that
these llleasures will reduce the capacity required for sediment
storage at the proposed reservoirs by about 5 percent. Consideration
was given to the fact that some land treatment measures in this
plall \iill become effective immediately after construction, '"hile
others will requiye several years from the start of the project to
becaee effective.