WSP01643

• File Number: 8543
• Description: Closed Basin Division
• State: CO
• Basin: Rio Grande
• Water Division: 3
• Date: 8/1/1984
• Author: USBOR
• Title: The San Luis Valley Project - Closed Basin Division - Facts and Concepts about the Project - Revised 1984
• Water Supply Pro - Doc Type: Publication

13

(.0
0)
.'--4
\"'"l

i:.:")

Both upland and wetland vegetation in the San Luis Valley and the
Closed Basin have been studied for many years. A 3-year growth study
was conducted by the Bureau of Reclamation on basically upland vegeta-
tio~, The study area was located where the water table was lowered by
a pilot salvage well. The study has shown that shrubs right around
project salvage wells will be adversely affected. Most of the shrubs
within several hundred feet of the well will De smaller in size and
fewer in number after several years of project operation. Younger
shrubs will most likely survive even near the wells. These shrubs have
the ability to follow the water table down as they continue to utilize
surface precipitation. Older shrubs do not respond to rainfall as
well,

':,:l

'.

The reaction of saltgrass and wiregrass to a lowering water tahle is a
little more complicated. Where the water table is more than 5 feet
down, most grasses depend on direct rain and snowfall for annual
growth. In these areas, project pumping and lower water tables will
not affect the grasses. In areas where a very high water table does
support stands of grass, lowering the water table will result in fewer
grass plants. Lower water tables and fewer saltgrass plants will allow
other grass species native to the area to increase. Grasses corning
into the area tvill De more valuable to livestock grazing. These
grasses will oe able to compete because of decreased surface salt accu-
mulations. Less desirable forage plants (saltgrass and wiregrass) will
share space with more desirable grasses (alkali sacaton, blue grama,
and western wheat).

There will be some reduction in plant vigor in wetland areas as a
direct result of project pumping. Federal law requires the replacement
of affected wetlands. The project will deliver water to the existing
Blanca Wildlife Habitat Area and llamosa Wildlife Refuge. A new
wildlife habitat area will be developed in the Russell Lakes vicinity.
A recreation area will be established in the San Luis and Head Lake
area, These steps will maintain both the overall quality and extent of
wetlands in the San Luis Valley and the Closed Basin sump area. These
steps will more than compensate for any wetland vegetation loss
resulting from project pumping.

Preliminary studies suggest that a program of establishing stabilizing
vegetation around salvage wells and the main canal should greatly
reduce long-term project maintenance costs. Shelter belts of trees and
starting stands of native grass in bare areas are being studied for
inclusion as part of the project design. Applying small amounts of
project salvage water for a short time after planting should allow
native plants to get well started. This program should result in a
significant increase in vegetation over preproject conditions in the
areas of the salvage vlells and main canal.

To sum things up, the direct effects of the project operations on
plants will be neither widespread nor severe. Vegetation effects will
occur only within the project b04ndaries. Visibly less vegetation may
result within 1,000 feet of some ~alvage wells. At distances farther
away from the wells, the change in vegetation (if there is any) will
only show up in careful scientific studies.