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315 required that the gaging stations be located in a self. formed reach of alluvial "'. stream channel, with a well-developed floodplain so that the channel could be considered to be in quasi-equilibrium. The mean-annual discharges for these stations range from 0.04 to 43.9 m3/s, while the drainage areas range from 51.8 to 9,660 km2 . Method of computing total sediment loads Total sediment loads were computed for the 15 gaging stations in the Yam- pa River basin using the streamflow-duration, sediment-trans port-curve method described by Miller (1951). This method is useful when the gaging-station records of streamflow are sufficient to determine the average duration of var- ious discharges, and the necessary data are available to construct a relation between total sediment-transport rate and discharge. The sediment discharge of a river is composed of two parts - the suspended load, which can be mea- sured readily, and the bedload, which must be computed in most instances. Therefore, separate relations describing the variation of the suspended load and the bedload with water discharge were developed. The relation between suspended load and discharge was determined by converting the measured instantaneous concentrations to daily suspended-sediment loads, and then plotting the loads against the corresponding daily mean discharge. A mean relation was calculated by a least-squares linear regression of the log-transform- ed data. The relation between bedload-transport rate and discharge was computed with the Meyer-Peter and Mueller (1948) equation, using a form derived by H.H. Stevens (pers. commun., 1978). The whole channel bedload-transport rate (Ib) is given by: Ib = (2.52 D90 1/4 il3/2 81/4 - 0.86Dm)312 W (2) where W = channel width D90 = grain diameter at the 90th percentile fraction u = mean velocity 8 = water-surface slope Dm = effective grain diameter (m) (mm) (m/s) (mm) The velocity, depth and width of flow for a given discharge were selected from discharge measurements made at the gaging station. The water-surface slope was measured over a reach of channel at least 20 channel widths in length, including the gaging-station cross-section. The size parameters of bed material were computed from sieve analyses of composited bed-material sam- ples collected at 6-10 sites across the stream channel at the gaging station. Several of the streams studied have a large range in size distribution of bed