WSPC05982

• File Number: 8541
• Description: San Luis Valley Project
• State: CO
• Basin: Rio Grande
• Water Division: 3
• Date: 6/1/1982
• Title: San Luis Valley Project Closed Basin Division - 1982 - Fish and Wildlife Report for the Closed Basin Division, San Luis Valley Project, Colorado
• Water Supply Pro - Doc Type: Report/Study

. .

"(u1' '0 7 '
. , 1,,1. .....

-'----.--.~.-...........

, . . - -, "" .. -, - _ ~~r-'" __~,

.

wetlands becomes "drier" due to drawdown pumping, more of the surface runoff will '
tend to infiltrate into the ground quicker. Retention'time of surface runoff in i
the existing wetlands could be reduced. This would be, a detrimental effect in the'
wetlands that receive water primarily from snowmelt surface runoff. However, it i~
impossible to quantify these impacts at this time.

c. Vegetation

(1 ) Impacts

(a) Pumping - The impacts of the project on vegetation
are related primarily to lowering of the water table due to drawdown. The impact
of lowering the ground water table would be the most observable in the area of
project well s.

For our determination, it was agreed that in the project area where the existing
water table is more than ten feet below the ground surface, there would be no
loss of vegetation, vigor and density resulting from the lowering of the water
table by the project.

The effect of lowering the water table a minimum of eight feet on vegetation where/,
the present water table is five to ten feet below the ground surface would be
minor. Our analyses indicated that about 2,154 acres of vegetation would be im-
pacted in the five to ten foot water depth. Most of the effect of lowering the
, water table would be observed in an area where the existing water table is less
than five feet below the ground surface. Approximately 8,944 acres of vegetation
would be adversely impacted in the zero to five foot water depth.

The total acres of vegetation adversely impacted in terms of reduced vigor and
density by lowering the existing water table would be 11,098 acres. Approxi-
mately 410 acres of vegetation adversely affected would occur on the Blanca WHA,
while about 190 acres are affected in the San Luis Lake and Head Lake Area.

d. Waterfowl Production

To determine the waterfowl production in the Closed Basin project area and the
associated loss in production caused by the project, the following calculations
(Tables 5 and 6) were made:

(1)

Table 5

Summary of Ducks Produced in the Closed Basin Project Area

43,122
- 2,235
40,887
x .31
12,675
+ 945
13,620

acres of wetlands in Closed Basin project area I
*acres of wetlands in San Luis/Head Lakes are (high density ar!

ducks produced/acre of wetland (low density area)
ducks produced/year fn low density area ' '
ducks produced/year in San Luis/Head Lake area (high density:
ducks produced/year in Closed Basin project area

*San Luis/Head Lake area is a high concentration area; and therefore,
production/acre is higher and was calculated separately from rest of
project area.

16