9469

• UCREFRP Catalog Number: 9469
• Author: Colorado Water Conservation Board.
• Title: Floodplain Information Report\
• USFW Year: 1995.
• Copyright Material: NO

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2.3 Basin Characteristics
The Gunnison River is a major tributary of the Colorado River. It has its origination at Almont,
Colorado, at the confluence of the Taylor River and East River in Gunnison County. Those
rivers have their headwaters in the Sawatch Range to the east and in the Elk Mountains to the
north. Additional tributaries originate from the east in the Sawatch Range and from the south.
The Uncompahgre River, which joins the Gunnison at Delta, is a major tributary with its
headwaters in the northern slopes of the San Juan Mountains. The watershed area at the
downstream limit of the study at Grand Junction is 8010 square miles. The elevation within the
watershed ranges from over 14,000 feet above Mean Sea Level at the headwaters to 4550 feet
at Grand Junction. The average slope within the study reach is approximately 9 feet per mile
with a maximum of 13 feet per mile in the upper reach and a minimum of 6 feet per mile at
Grand Junction.
The climate in the Gunnison River basin is classified as semi-arid and is characterized by low
precipitation, low humidity, and frequent wind. The primary sources of moisture are air masses
originating in the Pacific Ocean from October through April, and air masses from the Gulf of
Mexico during the late spring and summer. Normal annual precipitation ranges from
approximately 8 inches near Delta to more than 40 inches in the mountain regions. Occurrence
of precipitations is highly variable, with a large part of the total concentrated in several months.
The annual precipitation. occurs as snow from October to April. Rainfall can occur as
convective-type thunderstorms during the late spring and summer months generally over the
lower elevations of the basin, making August, September and October normally the wettest
months of the year. The Gunnison River basin, from its headwaters to the confluence with the
Colorado River, is shown in Figure 3.
2.4 Summary of Drainage Areas
The drainage areas for selected hydrologic points were determined through planimetering. The
results of the planimetering were then compared to known drainage area values at USGS gage
locations. The drainage areas at these selected hydrologic points are shown in Table 2.
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