WSP09829

• File Number: 8200.760
• Description: Yampa River General
• State: CO
• Basin: Yampa/White
• Water Division: 6
• Date: 1/1/1989
• Author: USGS
• Title: Simulation of Streamflow in Small Drainage Basins in the Southern Yampa River Basin - Colorado
• Water Supply Pro - Doc Type: Report/Study

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Region 1

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The distribution of precipitation is divided almost evenly among the four
seasons of the year. At the National Weather Service precipitation station at
Hayden, 27 percent of the average annual precipitation for a 30-year period
(1951-80) occurs during December, January, and February (National Climatic
Data Center, 1983, p. 2). An additional 25 percent of the average annual
precipitation occurs during March, April, and May. About 24 percent of the
average annual precipitation occurs during each of the periods of June, July,
and August; and September, October ,and November.

The seasonal distribution of annual precipitation does not change
greatly with increasing elevation. The gage at Pyramid is at an elevation
of 8,009 ft, and the winter and spring average annual precipitation is
28 percent each of the total. The summer and fall average annual precipi-
tation is 22 percent each of the total.

Although precipitation is somewhat evenly distributed throughout the
year, runoff from the small drainage basins in the study area primarily occurs
during the spring. At streamflow-gaging station Foidel Creek at mouth near
Oak Creek (09243900), 88 percent of the annual total runoff occurred during
the spring from 1976 through 1981. An additional 8 percent of the annual
total runoff occurred during the summer. Four percent of the annual total
runoff occurred during the fall and winter.

Late fall and winter precipitation is stored as snow and released as
snowmelt during the spring. Spring snow and rain augment .the melting snow-
pack. Runoff during the summer primarily is a continuation of the spring
snowmelt. Precipitation during the summer and fall generally does not.occur
as runoff downstream because much of this precipitation replenishes deficits
in the soil moisture. Thus, the precipitation-runoff system in these small
drainage basins begins with storage of moisture by snowpack accumulation
during the fall and winter, followed by a release of this water into the soil,
into the ground-water reservoirs, and to surface runoff during the spring and
summer.

Region L of the three hydrologic regions (fig. 1) includes the upper
reaches of Oak Creek and Trout Creek, the tributaries of Trout Creek, and
Cow Creek. In this region, drainage-basin divides generally are 8,000 ft
or higher. For example, the headwaters of Fish Creek, a tributary of Trout
Creek, are in the Dunckley Flat Tops and have a maximum elevation of
10,000 ft. The precipitation map (U.S. Weather Bureau, 1985) indicates that
total annual precipitation in region 1 is about 20 to 35 in. These drainage
basins have elevations between 6,500 and 7,000 ft in the low valleys. Annual
precipitation in the lower valley areas is about 20 in. Higher elevations
develop a fairly deep snowpack, and the effect of the increase in precipita-
tion is indicated by large stands of aspen. Runoff is derived from high- and
low-elevation areas. Depending on the particular spring melt sequence, two
separate runoff peaks may be identified on a hydrograph. Melt from the lower
elevations causes an initial runoff peak, and melt from higher elevations can
lag by as much as 1 month. A single- or multiple-peaked snowmelt-runoff
hydrograph may result depending on spring weather patterns.

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