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2.7.4.2 Surface Water Quality <br />l <br />Seasonal variation in water yield for the Yampa and Williams Fork Rivers have <br />been previously discussed. The variation in yield causes a corresponding varia- <br />tion in water quality of these streams. Total suspended sediment loads are at a <br />maximum during peak flows associated with spring runoff. Steele (1979) reports <br />that up to 90 per cent of the annual sediment load of the Yampa River at the <br />Maybell station is discharged during the period of snowmelt runoff. Figures <br />2.7-11, 2.7-12 and 2.7-14 present the graphs of suspended sediment and discharge <br />for the Hayden and Craig sites on the Yampa and the mouth of the Williams Fork <br />rivers respectively. Dissolved solids loads show the opposite relationship to <br />suspended solids. High quality snowmelt runoff contains relatively low levels of <br />total dissolved solids (TDS). Therefore, concentrations of TDS decrease during <br />peak flow periods. In the summer and early and middle winter when ground -water <br />discharge makes up a larger percentage of the flow in the rivers, TDS values <br />increase. The Colorado Water Conservation Board reports that intermittent <br />streams at lower elevations produce most of the dissolved and suspended solids <br />that leave the basin. Tables 2.7-13 and 2.7-14 show discharges and selected <br />chemical data for the Yampa and Williams Fork rivers, respectively. <br />• 2-415 <br />REVISED FEB 13.87 <br />