<P> Upon completion of Glen Canyon Dam on September 13 , 1963 , the Colorado River began to back up , no longer being diverted through the tunnels . The newly flooded Glen Canyon formed Lake Powell . It took 11 years for the lake to fill to the 3,700 feet ( 1,100 m ) level , on June 22 , 1980 . The lake level fluctuates considerably depending on the seasonal snow runoff from the Rocky Mountains . The all - time highest water level was reached on July 14 , 1983 , during one of the heaviest Colorado River floods in recorded history , in part influenced by a strong El Niño event . The lake rose to 3,708.34 feet ( 1,130.30 m ) above sea level , with a water content of 25,757,086 acre feet ( 31.770898 km ) . </P>
<P> Upon completion of Glen Canyon Dam on September 13 , 1963 , the Colorado River began to back up , no longer being diverted through the tunnels . The newly flooded Glen Canyon formed Lake Powell . It took 11 years for the lake to fill to the 3,700 feet ( 1,100 m ) level , on June 22 , 1980 . The lake level fluctuates considerably depending on the seasonal snow runoff from the Rocky Mountains . The all - time highest water level was reached on July 14 , 1983 , during one of the heaviest Colorado River floods in recorded history , in part influenced by a strong El Niño event . The lake rose to 3,708.34 feet ( 1,130.30 m ) above sea level , with a water content of 25,757,086 acre feet ( 31.770898 km ) . </P>
when was the last time lake powell was full
when was the last time lake powell was full
July 14 , 1983
July 14 , 1983