WMOD00432

• Title: Colorado River Augmentation Demonstration Program - Finding of No Significant Impact
• Date: 9/1/1985
• Weather Modification - Doc Type: Report

Streamflow varies greatly from season to season, with high spring anr:l
early summer runoff reduced to almost nothing in late summer and
fall. Irrigators and local governments have constructed over 100
small reservoirs on Grand Mesa to even out the water supply over the
season by erecting small dams at the outlets of some of the natural
lakes. The Grand Mesa reservoir system and all streams tributary to
it are operated as a "pool". Reservoirs are usually f~l by
mid-June, and stored water is released from late June or early July
to about November 1. By the end of the summer, irrigation demands
have reduced the water supply until practically all streams in the
farming areas consist of return flows.

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On Grand Mesa, water at the higher elevations is of excellent
quality for domestic use. Water at lower elevations is suitable
for domestic use and irrigation. Return flow waters from irriga-
tion are marginal for reuse unless blended with high quality
direct flows or storage releases.

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Impacts. - The proposed limited research program would not signi-
ficantly alter the timing or amount of precipitation in the area, and
no significant effects on streamflow, water quality, or irrigation
would occur as a result of the program.

3. Soils and Vegetation

Soils on Grand Mesa have developed ~ situ out of parent material and
are low to moderate in fertility. The soil supply is essentially
fixed, renewing itself by the slow weathering of bedrock over time.
Soil management focuses on reducing erosion.

Vegetation zones above 9000 feet include the subalpine and montane
lones, where meadows and numerous lakes are interspersed with
stands of spruce, aspen, and fir trees. Sagebrush, grasses and
flowers are found in open parks. Common shrubs include elder-
berry, black currant, wil d raspberry, snowberry, Colorado dogwood,
and chokecherry. Grass species include bluegrasses, bromes,
fescues, and wheatgrasses. Typical flowers are delphinium,
larkspur, lupine, columbine, aster, bluebell, and buttercup.

Impacts. - The minor amount of increased precipitation produced
during the proposed program would not significantly affect soil ero-
sion or this vegetation.

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4. Fish

The natural lakes and some reservoirs have resident cutthroat and
eastern brook trout populations. The shallow reservoirs do not
maintain good fisheries. The Colorado Division of Wildlife stocks

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