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'" . . . ::, '" "- . 2.3 Basin Characteristics - '" ~ ~ ~ N '" 0 N -------- *001:> ------j The Gunnison River is a major tributary of the Colorado River. It has its origination at Almont, 0 ----- ~ -. 1 Colorado, at the confluence of the Taylor River and East River in Gunnison County. Those .. Creek E I rivers have their headwaters in the Sawatch Range to the east and in the Elk Mountains to the j I '" 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 . '" ~ 0 headwaters in the northern slopes of the San Juan Mountains. The watershed area at the I ~ ;.., I downstream limit of the study at Grand Junction is 8010 square miles. The elevation within the 0 c: 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 " ::E with a maximum of 13 feet per mile in the upper reach and a minimum of 6 feet per mile at t: 0 U Grand Junction. "- ILl Oz !l . ~ tn- cr; <C <C 0:: ~ The climate in the Gunnison River basin is classified as semi-arid and is characterized by low -...... CD ILl -a.. ,,:> nO.!8 , > precipitation, low humidity, and frequent wind. The primary sources of moisture are air masses <.> 0:: originating in the Pacific Ocean from October through April, and air masses from the Gulf of :x: Cr ~ 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 on :n 0 of precipitations is highly variable, with a large part of the total concentrated in several months. 0 I ~ The annual precipitation occurs as snow from October to April. Rainfall can occur as I I I 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 ~ 0 months of the year. The Gunnison River basin, from its headwaters to the confluence with the E .. ILl ;;: Colorado River, is shown in Figure 3. '0 . . '" '" z 0 ~ 0 - <C 2.4 Summary of Drainat!e Areas 0:: ~ Cl fO 5 The drainage areas for selected hydrologic points were determined through planimetering. The U results of the planimetering were then compared to known drainage area values at USGS gage . . 8 locations. The drainage areas at these selected hydrologic points are shown in Table 2. "- "- 0 0 - .. I N I ~ I VI ~ < 0 Cl:l > ii ~ Co W!IJYI . 0 <0 0 " '" I , , I , , I I "'i :" I 0 I r- ------ 4 . ::, '" Co ;... " ~ M ~ "