Glen Canyon Dam in June, 1983. Lake Powell filled for the first time during the big flood of 1983. Well over 100,000 cfs was entering the lake, but the spillways and power plant were only designed to release 90,000 cfs. The Bureau quickly found out that if both spillways were operating, harmonic vibrations threatened the integrity of the entire structure. With the resulting net inflow of over 40,000 cfs, the Lake threatened to top the dam, so the Bureau was forced to put huge boards on top the dam until the flood subsided. The Bureau managed to fix the damaged spillways in time to release enough water to prevent the 1984 flood from causing the dam to fail. Boaters had terrifying rides in the big rapids and whirl pools.

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