Hyrum Reservoir , Utah, was studied for one year during an artificial destratification project. Previously Drury et al. (1975) had studied Hyrum Reservoir for one year of stratified and one year of destratified conditions. The redistribution of dissolved oxygen to the hypolimnion significantly changed conditions for chemical and biological activities in the lower depths of the reservoir. The Aphanizomenon bloom increased with each year of destratification. The reservoir was changed by destratification so as to be suitable habitat for trout on a year round basis. Aerobic condi tions prevented iron from being released from the sediment into the aqueous phase . In summary the water quality of Hyrum Reservoir was highly affected by algal blooms, the interaction of bottom sediments with overlying waters especially in conjunction with spring and fall overturn, and the impact of materials and water flow from the Little Bear River.