WSP12345

• File Number: 8240.200.10.B
• Description: UCRBRIP Annual Reports
• Basin: Colorado Mainstem
• Date: 1/12/1995
• Author: UCRBRIP
• Title: 1994 Annual Reports Package Part 2
• Water Supply Pro - Doc Type: Publication

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The mild winter in nonh-eastem Utah resulted in slow cooling of water temperatures in the Gf~n Rjver.
Water temperatures at the USGS gage near Jensen, lIT dJd DOl reach freezing until February 2. Temperatures
below 1.0 'C lasted for only 4 clays before beginning 10 warm. Daily watef temperatures (daily instantaneous
values) lor the Gr~n River near Jensen during the winter of 1993-94 are plotted in Figure 5.

Diel changes in main-channel water temperature during the first ice measurement trip (January 31 - February
4) typically ranged from .0.05 to O.3O'C Gr~n River Mter temperatures in each reach were similar with a
range of .0.05 to 0.32'C in Reach I, .0.10 to 0.38"C in Reach 2, and 0.4 10 O.5'C in Reach 3. No signifioant
differences water temperatures were noted betw~n reaches. During the second winter ice measurement
(February 21-24) water temperatures were warmer, ranging from 0.62 to 3.66'C during the trip.

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Figure 5.

Water temperature in the Green River, l.993-94, as reaJnled at lbe USGS stream gage near
Jensen, Uf, 1"emperatu= are daily Instantaneous values.

5.2 . ICE CONDmONS

Due to the warm winter. there was very little ice formation on the Green River between IslaDd Park and
Ouray, UT. Ice formation began the morning of January 30 and continued for approximately 5 da)5. After
this shon rold period. air and water temperatures steadily increased, allowing no additional ice formation
during the year. This period of ice formation was much shoner than observed by Valdez and Masslich (1990)
during the winters of 1986-87 and 1987-88. Figure 6 illustrates the beginning and duration of river ice
formation overlaid on river waler temperatures and minimum cIaily air temperatures recorded near Jensen,
UT for winters 1986-87, 1987-88 and 199384.

5.2.1 Frazn Ice

FraziI ice formed on the Green River during two shon periods. Fruil ice was first observed during the week
of January 31 through February 4. During this period.!razil ice was formed in the upper sections of the study
area. principally in Whirlpool and Split Mountain C3nyollS. In the lower, slow water sections below Dinosaur
National Monument, the suspended frazil ice noated to the surface forming large 1DalS. These mats, termed
liIy-pad ice', were typically 5 to 100ft in diameter and 1 to 1.5-ft thick. Lily-pad ice was thick, covering most
of the river surface in the Jensen area. FraziI ice production stopped as air temperatures warmed leaving
Reaches 1 and 2 clear of fraziI and lily-pad ice by 1400 hrs.

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