FLOOD10262

• County: Alamosa
• Basin: Rio Grande
• Title: Report on Governor's Emergency Funding 1987 Rio Grande Flooding
• Date: 7/15/1987
• Prepared For: Alamosa County
• Floodplain - Doc Type: Flood Documentation Report

1.0 PURPOSE

During the Spring of 1987, the San Luis Valley was predicted to
receive high flood waters. An effort to divert flood water from
the Rio Grande above the communities of Monte Vista and Alamosa
was undertaken by local government and private interests. This
report will evaluate the use of irrigation ditches for flood
control in the San Luis Valley.

2.0 REPORT AREA

The report area is comprised of both Alamosa and Rio Grande
counties in the San Luis Valley. The area is bounded on the west
and north by the Continental Divide, on the east by the Sangre
de Cristo Range, and on the south by the borders of Rio Grande
and Alamosa Counties. The Valley floor is nearly flat, sloping
from about four to ten feet to the mile. The northern part of
the Valley lies within a closed basin with no surface drainage
outlet. This basin is separated from the Rio Grande drainage by
a low lying ridge several miles wide.

Over one third of the land in the study area is
owned. It includes national forests, pUblic domain,
refuges and the Great Sand Dunes National Monument.

federally
wildlife

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I

The frost-free season in the Valley ranges from about 90 to 115
days. Precipitation averages about seven inches a year.
Generally, soils of the Valley are coarse textured next to the
mountains and are a little finer textured toward the center of
the Valley. They are underlain mostly with sand and gravel at
depths of one to four feet. During good water years.
appreciable acreage along the west side of the Valley is
completely or partially subirrigated.

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The main irrigated crops are alfalfa. potatoes, barley, oats,
grass. hay. and pasture. Native hay or pasture on high water
table areas are an important part of many farms and ranches.
Crop yields are generally high and quality of adapted crops
unusually good.

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2.1 HISTORY

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The settlement at San Luis, the oldest town in Colorado. led to
the construction of ditches and the oldest court decree for
irrigation (April 10, 1852) in Colorado. By 1900 some 1.800
miles of canals and ditches had been constructed. A large
network of irrigation canals was built during 1880-1890 to
irrigated lands in the eastern and central parts of the closed
basin. By 1915 most of the area around Mosca and Hooper became
waterlogged because of this irrigation.

Ora i nage sys t ems
waterlogged lands

constructed
alleviated

bet'./een
some 0 f

1911
the

and 1921
problems

to
but

reclaim
created

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