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)0 Turbidity on the Green River was closely related to seasonal fiuctuatione in s'b-eam--tlow. During the spring and early summer, the river was extrell181y turbid, in July as the high waters began to oub- side, the 8D>UJ1t of suspended solids gradually decreased. The greatest depth of risibility observed in the Green River during the study was 1at inches, measured at Split Mountain Campground, NovoJDber 4, 1962. This pattern of gradual reduction in suspended solids during the su.mroer and tall. was interrupted by oocasional rains which caused the river to become extremely turbid for short periods. The water after these rains was usually dark red in oolor or sometimes yellow. Variation in turbidity in the rampa laver followed a pattern similar to that found in the Green River. Seasonal fiuctua tions were , ! i 1.. muoh JlIOr8 extreme, however. During the high ''later periods of spring and early SUJIIil8r, turbidities were oomparable to those found in the Green River. Turbidity during the low water seasons of late summer and fall will be disaussed in the following chapter. Apparently there is litUe direct effect of suspended material on fish unless the concentration is exceedingly high (Hallen, was usually greatly reduced. The possible effects of temperature and turbidity variations between the Green and Yampa rivers on distribution of the fish fauna 1951; Doudoroff, 1957; Hynes, 1960). \~al1en's study of the direct etfect of turbid1 ty on fish indicates that concentrations of silt particles up to approximately 20,000 ppm for prolonged periods do not produce any noticea.ble behaviorial reactions. The abUity of .fish to move through water containing suspensoids \n. thout injury to the gUls has been demonstrated by Cole (1941). An instance of mechanical injury through abrasion by sharp angular particles is l'eported by Paul (1952).