Discharge of the Yellowstone is lowest during winter months prior to 

 spring runoff. Excessive water withdrawals for industrial use in this 

 period of low flow would take its toll on benthic organisms. This would result 

 not only from further reductions in velocity and wetted bottom area, but from 

 the increased dangers of ice accumulation. Formation of anchor ice in riffle 

 areas at night tends to impede the flow. As ice melts during the day, the 

 churning action of loose ice scours the benthos, removing algae, detritus, 

 and invertebrates (Hynes 1970, Maciolek and Needham 1951). 



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