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: /~ars. Development of water resources in the Yampa River basin can affect the ,/ geomorphology, hydrology, and ecology of the river by changing the timing or // magnitude of streamflow and by causing an imbalance in the sediment budget. A technique has been developed to estimate how the sediment load through Deerlodge Park andi nto Yampa Canyon immediatelY downstream would change in response to altered or reduced streamflow and sediment supply. This informa- tion, in turn, cap be used to develop scenarios on how the Yampa River at Deerlodge Park and in Yampa Canyon might respond. River stage was recorded and discharge was measured at a new streamflow- gaging station, 09260050 Yampa River at Deerlodge Park, during the 1982 and 1983 water years. Discharges recorded at this site correlated well (R2=0.98) with the sum of discharges recorded during the same period at two U.S. Geolog- ical Survey streamflow-gaging stations in the drainage basin upstream: 09251000 Yampa River near Maybell and 09260000 Little Snake River near Lily. The sum of historic discharges recorded at Maybell and Lily were used to estimate historic discharges at Deerlodge Park. The period 1941 through 1983 was used to estimate mean annual streamflow at Deerlodge Park. A streamflow-duration curve was derived from the combined record (fig. 6), and mean annual streamflow was determi ned to be 1. 5 mill i on acre feet per year. ,Sediment data were collected at station 09260050 Yampa River at Deerlodge Park to compute the mean annual sediment load transported through Deerlodge Park and into the Yampa Canyon. Suspended-sediment discharges and bedload transport rates were measured 32 times throughout a range of water discharge during 1982 and 1983. Bed material as well as bedload in the Yampa River at Deerlodge Park predominantly consisted of medium to coarse sand; the median grain size was about 0.60 mm. Silt- and clay-size material constituted a 1 arge part of the suspended load, and averaged 40 percent of the total suspended-sediment load. . 'iJaily sediment di scharges were computed from instantaneous measurements according to stand$rd U.S. Geological Survey procedures (Porterfield, 1972); in add.ition, they were estimated with the Modified Einstein procedure (Colby and Hembree, 1955) for comparison. Suspended-sediment discharge, bedload discharge, total sediment discharge and various size fractions of the total sediment discharge are presented as linear functions of water discharge in tables 3 and 4. As a test of the significance of seasonality in sediment di scharge, a Student t-test was performed on slopes and intercepts of the measured transport rate relations; no differences were fOund at the 95-percent level that could be attributed to seasonality. , Therefore, separate transport equations for rising and recessional discharge periods were not used. Annual sediment loads 'were computed using the historic frequency distri- bution of streamflow and sediment transport equations based on both measured sediment di scharges and sedi ment di scharges est imated \~ith the Modifi ed Ei nstei n procedure 0.1i 11 et, 1951). ,;nnual total sediment i oad based on "'e'suro...l ,:::oc';l"I'IGI""I" ...:,::,-......-""....os ,.-(: 2 "'.1 ",,':'1 it"'ln .0n/'Y~ -n" -n~ua' ..,..,.,....1 s'o'- .f'..... '.1.. _... 11..,-.,... v'i.'.:'':'[-;.I:_ ,'{i:"._- .\".'~ H;,l I, ."" l~; _ \ I, c.J I... 0. I: l ;"';"o;J __"j ment load based on Modified Einstein procedure estimates of sediment discharg- es was 2.42 million ton/yr. Annual suspended sediment load was approximately 1. 9 mi 11 ion ton/yr, Scour duri ng hi gh f10ws exposed bedrock at one part of the cnannel at the Deerlodge Park study site. Due to the nature of computa- tions involved, this may have caused the Modified Einstein procedure to 31 ....---."