9601

• UCREFRP Catalog Number: 9601
• Author: Montgomery Watson.
• Title: Yampa River Basin - Small Reservoir Study Phase 2 Report.
• USFW Year: 2000.
• USFW - Doc Type: Steamboat Springs, CO.
• Copyright Material: NO

August 2000 CRWCD * Yanpa Ricer Basin .Small Reserwir Study - Phase 1 Report * Page ? 3
2.0 PROJECT BACKGROUND
2.1 GENERAL
' 2.1.1 Basin Hydrology
' The Yampa River drains an area of approximately 9,500 square miles in northwestern Colorado and
south-central Wyoming. In Colorado, most of Moffat and Routt counties, along with small sections
of Garfield, Grand and Rio Blanco counties drain into the Yampa River. Portions of Carbon and
' Sweetwater counties in Wyoming are drained by the Little Snake River, a major tributary entering the
Yampa River downstream of Maybell, Colorado. This study only covers those portions of the basin
that are located in Colorado. The study area also includes Vermillion Creek, which is tributary to the
Green River in Browns Park. While Vermillion Creek is not technically part of the Yampa River
' basin, it is within the CRWCD's boundary, and is included in this study because of its' geographical
proximity to the basin. Figure 2, Yampa Ricer Basin Drainages, presents Yampa River sub-basins.
' In 1922, the waters of the Colorado River basin were apportioned by the Colorado River Compact for
use between the upper and lower basin states. The upper basin allocation was further apportioned by
the Upper Colorado River Basin Compact of 1948 (1948 Compact). This compact addressed
' allocation of the Yampa River between Colorado and Utah, and stipulates that Colorado users will not
cause the Yampa River at the Maybell gaging station to be depleted below an aggregate flow of 5
million ac-ft (maf) for any period of 10 consecutive years. Hydmshpere (1993) reported that the
average annual historical flow at the Maybell gage is 1.135 maf and the minimum historical 10-year
' sum is 9.1 maf.
Most of the yield of the Yampa River basin is produced by melting snowpacks in the higher elevations
' in the eastern part of the basin. Streamflow is highly seasonal, typically peaking in late spring/early
summer and rapidly declining through the summer months to base flow. Approximately 64 percent
of the 1.1 maf of annual stream discharge recorded at the Maybell, Colorado gage occurs in May and
' June. Water yield also varies spatially across the basin, reflecting spatial climatological variation.
Annual precipitation ranges from more than 50 inches in the high alpine zones in the east and south
to negligible amounts in the and western portion of the basin (United States Forest Service [USFS],
1993; Natural Resource Conservation Service [NRCS], 1999).
' There are 21 operating streamflow gages in the basin (United States Geological Survey [USGS], 1999;
Colorado Division of Water Resources [CDWR], 1999). Most of these gages are on the mainstem
' Yampa River or major tributaries. Approximately 63 other gages have been operated by the USGS in
the basin over various periods in the past, but have been discontinued. Most of these gages were
located on tributary streams, with contributing drainages ranging from less than ten to over 200
' square miles. During Phase 1 of this study, streamflow data from 35 existing and historic gage
stations were used to calculate inflow hydrology for potential reservoir sites. Figure 3, Loavibn of
F Rarer Basin Gaging Stations, displays the locations of the gaging stations that were utilized during
' this study. Appendix A, Estimate of Amoral Yield for Gaged Basin Shwas, summarizes estimated annual
yield and yield per square mile at these stations.
2.1.2 Water Use
The major consumptive water use in the basin is agriculture. Municipal and industrial depletions are
much smaller, but are very important economically. Recreation is becoming more and more
' important economically and will probably experience significant growth over the long-term.
1
' MonVreery Watson *P.O Box 774018 * Strcorhxit Sprvtgs, Colorado 80477 * [phone]
W/WP10J51M-2R¢vt
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