earlier on the Yellowstone River than the Missouri River. Ice 

 floods can alter channel banks and vegetation and can scour the 

 river bed. 



The second, much larger peak flow spans the period from early 

 May until early August and is a result of mountain runoff (Figure 

 2) . It is during this period that many side channels are filled 

 when at other times of the year they may be dry or only backwaters. 

 These high flows tend to scour the bottoms of side channels and 

 remove sediments deposited during low water periods. High flow 

 maintains the integrity of the river channel and islands (Peterman 

 1979 and Martin 1977) . Large amounts of suspended sediments are 

 carried by the Yellowstone during this time of year. Except for 

 this mountain runoff period little stream bank vegetation contacts 

 the water and very few macrophytes are found in the river. 



Elser and McFarland (1977) and Rehwinkel (1978) found spawning 

 migrations of Yellowstone River fish in the lower Tongue and Powder 

 rivers. These two streams have similar flow patterns as the 

 Yellowstone River. The Powder River has much greater 

 concentrations of suspended sediment than both the Yellowstone and 

 Tongue rivers. The greatest concentrations of suspended sediments 

 occur in these two tributaries during periods of runoff or 

 precipitation. Despite the turbid nature of these 2 rivers, the 

 major substrate is fine pebbles often intermixed with fine coal. 

 Flow in both streams is generally confined to a single channel. 

 Because of low flows in late summer and early fall, there are few 

 resident game species in the lower reaches of these two rivers. A 



12 



