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e It is not uncommon in Colorado for flooding to occur in the spring from snowmelt and in the summer from rainfall, with the type of flooding most critical to an area dependent primarily on the elevation and location of the watershed. Average snowfall amounts within the river valley show considerable variation, with approximately 34 in at Grand Junction, 40 in at Rifle, and 70 in at Glenwood Springs. During a wet year, the mountainous regions of the upper watershed may have over 400 in of snowfall. In late October, snowpack usually begins to accumulate, with snowmelt beginning in late April and continuing through early July. Typical snowpack water equivalence, at elevations above approximately 9,000 ft by April 1, equals 16 in, and varies from 9 to 24 in during dry and wet years, respectively. 3. Average Runoff Numerous stream-gaging stations, located along the main stem of the the major tributaries. operated by the USGS, are Colorado River as well as on e The records of the two stations listed below were used to estimate the long-term runoff and develop flow-duration curves at the Webster Hill dam site. Station Nuntler Station Name and Location Period of Record 09085100 09093700 Colorado River below Glenwood Springs Colorado River near DeBeque I966-Present 1966-Present e The Glenwood Springs gage is approximately 36 mi upstream from the project site and has a drainage area of 6,013 sq mi; the DeBeque gage is about 19 mi downstream of the project site with a drainage area of 7,370 sq mi. The average annual gaged flow below Glenwood Springs equals 3,254 cfs; at the DeBeque gage, the average annual flow equals 3,511 cfs. Prorating the 3686-a/5 1-6