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<br />.'"
<br />
<br />1014
<br />
<br />E. D, ANDREWS
<br />
<br />TABLE I. SUMMARY OF MEAN ANNUAL INnOW AND OUTfLOW OF WATER AND SEDIMENT TO SELECTED REACHF5 OF TllE GREEN RIVER BEFORE AND AFTER TllE
<br />CONSTRUcnON OF FUMING GORGE RESERVOIR
<br />
<br /> Period of Drain.. ~rescrvoir Poa-raervuir
<br /> oodimenl record .... Mean .nnual S"'pendftl Mean "Dual Suspended
<br /> (w....ya..) (mil) d""harae !Cdim(nt disc!wl< _meal
<br /> (ft3/.) (10.. . 106/yr) (ftJ/.) (IOID x 10611")
<br />RtGC~1
<br />loj/o..
<br />G...n Rj.., 01 G.....we. Ullb 19S6-1959 U.09O 2,IJO 160 2,130 0
<br />Linle Snake ., Lily, Colorodo 1958-1964 3,7JO 171 lJ9 m \.29
<br />"tlm.. near Mlyben. Colondo 1950-1958 3,410 1,470 .388 1,470 .388
<br />Rod C...k near DUlCb Jobn, UIIb 1971-1977 140 7.76 .0844 7.76 .0844
<br />UnpIN '1'tI 3,030 141 III 20 U5
<br />rolDl 25,400 4,320 6.'12 4,199 3.31
<br />OIujIow
<br />G.... Ri.., I' J....... UIIb 1947-1979 25,400 4,320 6.92 4,199 3.21
<br />RtGC~l
<br />'''flow
<br />Grern River I' Jensen. Utah 1947-1979 2',400 4,320 6.92 4,199 3.21
<br />While River I' mouth 1974-1982 ',120 632 1.67 654 1.67
<br />Un''Ied arel 4,980 498 4.18 741 4.18
<br />rolDl 35,500 ',450 12.8 5.500 9.06
<br />o.tj/o..
<br />Green River .1 OuJ'l", UWI 1951-1966 35,500 5,450 12.8 5.500 6.61
<br />RtGCAJ
<br />loflow
<br />Green Ri.., I' Ouray, Ullb 1951-1966 35,500 5,410 12.8 5.500 6.61
<br />Pricz Ri,., I' Wood.lide, Ullb 1975-1982 1,540 10' 2.18 105 2,18
<br />UnPled .... 3,S60 275 2.04 -200 2.64
<br />r...1 40,600 5,830 17.0 5,805 10.8
<br />o.rjIo..
<br />Green River II Green River, Utah 1944-1982 40,600 5,830 17.0 '.5800 8.83
<br />.-200 ftJ/.lre divened upssream lrom.... PF.
<br />
<br />Gorge Reservoir had begun. These tributaries,
<br />however, have not been affected significantly by
<br />any regula lion or impoundment. Mean annual
<br />values shown in Table I, therefore, are a reason-
<br />able estimate of inl10w and outl1ow of water and
<br />sediment to reaches of the Green River prior to
<br />appreciable water-resources development. The
<br />estimated contributions from ungaged areas
<br />were computed by assuming that inl10w and
<br />outl1ow to the reaches were equal. In terms of
<br />the sediment budgets, this assumes that the
<br />reaches were in long-term quasi-equilibrium
<br />prior to I10w regulation. The presence of exten-
<br />sive I100d plains along most alIuvial reaches
<br />supports this assumption.
<br />
<br />{J
<br />
<br />SOURCE AREAS OF RUNOFF
<br />AND SEDIMENT
<br />
<br />Water and sediment are not contnbuted to
<br />the channel network uniformly across the Green
<br />River basin (loms and others, 1965). Further-
<br />more, the principal source areas of water and
<br />sediment differ greatly. A majority of the annual
<br />water discharge from the basin is supplied by the
<br />headwater areas. Conversely, the semiarid parts
<br />of the basin at lower elevations contribute most
<br />of the sediment. The mean annual water dis-
<br />charge and sediment discharge prior to 1962 at
<br />gaging stations in the Green River basin are
<br />
<br />shown in Figure 2, Immediately upstream from
<br />Flaming Gorge Reservoir, the unregulated mean
<br />annuall10w was 1,575 ftJ Is or 27% of the total
<br />basin outl1ow. The mean annual sediment dis-
<br />charge at this gage, however, was only 0.37 x
<br />106 tons or 2.2% of the basin outl1ow. Similar
<br />contrasts are shown by the comparison between
<br />the water and sediment discharges of the Green
<br />River basin and the quantities measured by the
<br />farthest upstream gages on the Yampa and
<br />White Rivers. The combined mean annual dis-
<br />charge at the 3 farthest upstream gages is 2,680
<br />ftJ Is or 46% of the basin discharge, whereas the
<br />sediment contribution is only 0.44 x 106 tons or
<br />2.6% of the basin-sediment discharge. The con-
<br />tributing drainage area is - 27% of the total
<br />basin.
<br />The large sediment-contributing areas in the
<br />Green River basin are indicated, similarly, in
<br />Figure 2. All tributaries joining the Green River
<br />downstream from the gage near Green River,
<br />Wyoming, supply relatively large percentages of
<br />the basin-sediment outflow. In all instances, the
<br />sediment is contributed primarily by the down-
<br />stream part of the tributary drainage basins.
<br />Thus, the large water-contributing parts of the
<br />Green River basin lie around the rim, especially
<br />along the northeast divide. Conversely, the large
<br />sediment-contributing areas are located in the
<br />central and southern parts of the basin.
<br />
<br />CHANGES IN CHANNEL
<br />EQUILIBRIUM DOWNSTREAM OF
<br />FLAMING GORGE RESERVOIR
<br />
<br />The mean annual inl10w and outflow of
<br />water and sediment to three reaches of the
<br />Green River after the construction of Flaming
<br />Gorge Reservoir are summarized in Table 1.
<br />Comparing the pre- and post-reservoir periods,
<br />mean annual water discharge at the Green River
<br />near Jensen, Utah, gage has not been affected.
<br />Mean annual discharge of the Green River near
<br />Jensen, Utah, gage was 4,200 ftJ Is from 1963 to
<br />]981 compared to 4,320 ftJ/s from 1947 to
<br />1962. The range of daily I10ws throughout the"
<br />year, however, has been altered considerably
<br />and will be discussed below. The mean annual
<br />sediment discharge at the Jensen gage bas de-
<br />creased by 54% to 3.21 x 106 tons. Mean annual
<br />inl10w of sediment to the river reach down-
<br />stream from Flaming Gorge Reservoir to the
<br />Jensen gage is 3.31 x 106 tons. Thus, there exists
<br />a near balance of sediment supply and transport
<br />in this reach of Green River after regulation.
<br />Downstream from Flaming Gorge Dam, the
<br />Green River flows through a narrow, bedrock
<br />canyon for 12 river miles. Degradation of tbe
<br />riverbed in this reach has been limited. In 1982.
<br />bed material in this reach consisted primarily of
<br />coarse gravel, cobbles, and boulders. Photo-
<br />
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