FLOOD10357

• Document ID: 123
• County: Rio Grande
• Stream Name: Alamosa River
• Basin: Rio Grande
• Sub-Basin: Alamosa - Trinchera
• Water Division: 3
• Title: Alamosa River Watershed Project Literature and Watershed Assesment, Final EPA Report
• Date: 9/30/2003
• Prepared For: Valle del Sol Community Center
• Prepared By: US Environmental Protection Agency
• Watershed Pro - Doc Type: Project Report

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The USGS performed a vegetation survey in the San Luis Valley including the Alamosa
River Watershed up to the Summitville Mine. The USGS used Airborne Visual and Infra-
Red Imaging Spectrometry to evaluate vegetation species and areas showing stress.
This spectrometry technology allows the vegetation and cover on an entire watershed to
be photographed and evaluated on a watershed basis (16).

Noxious weeds are a threat to agriculture in the Alamosa River Watershed and
throughout the State of Colorado. The damage to farmers in Colorado is well over $35
million per year. Potential damages in the watershed occur due to a loss of crop
production and ecological habitat when weeds take over and expensive weed control
practices are necessary.

The Conejos County Weed Board conducted a weed survey in 1993 for several main
weeds of interest, Canada Thistle, Spotted Knapweed, Leafy Spurge, Tall White Top
(Iron Weed), Knapweed, Horace Cress and Quackgrass (6). The problem areas include
road right of ways, private pasture land, USFS property, ditch banks and fence lines. In
2001, the Conejos County instituted cost sharing a weed control plan with landowners
using contracted certified sprayers (17). The plan does not reference spraying
procedures to protect sensitive environmental areas such as wetlands or tributaries.

3.7 Timber Harvesting

Timber harvesting is recognized as a viable resource in the Rio Grande National Forest.
Harvest operations will be managed by the USFS to emulate small-scale disturbance
events or processes (13). Timber harvesting would have an enormous impact on the
watershed from the construction of roads, soil erosion, and sediment loading into the
river. Conejos County has identified areas of high risk for fires. It is not known if the
USFS is considering timber thinning as a way to reduce fire risk. No information was
found regarding past and future logging operations.

3.8 Climate

In the winter, the average temperature is 21.60 F and the average daily minimum
temperature is 40 F. The lowest temperature recorded is -340F (January 12, 1963). In
the summer, the average temperature is 61.40F and the average daily maximum
temperature is 79.60F. The highest recorded temperature was 940F (July 13, 1971).

The total annual precipitation is 5.52 inches; 71 percent falls in April through September.
The heaviest rainfall recorded was 1.45 inches. On an average, there are 44
thunderstorms each year, thirty that occur in the summer season. Average snowfall in
the mountains is 28 inches. The maximum daily snow total recorded was 11 inches in
the watershed. The growing season in the area averages 110 days.

The relative humidity in spring is less than 35 percent, the remaining year it is
approximately 45 percent. The percent sunshine is 77 percent in the summer and 73
percent in the winter. The prevailing wind is from the south-southwest with an average
wind speed of 10.4 miles per hour in April (9).

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