According to the National Park Service at Glen Canyon National Recreation area, storage of water at Lake Powell
began March 13, 1963 and reached full pool (3,700 feet) the first time on June 22, 1980. Lake Powell's volume is 27,000,000 acre feet with a surface area of 266 square
miles. The lake is approximately 186 miles in length and there is approximately 1,960 miles of shoreline with 96 major side canyons. Average annual evaporation is 2.5% of the
volume. The water depth at the dam is 560 feet.
The annual legal minimum outflow at Glen Canyon Dam is 8,230,000 acre feet with the daily at 5,000 to 20,000 cubic
feet per second (cannot exceed 8,000 cfs variation in a 24 hour period). The maximum flow at flood time is 322,000 cubic feet per second (31,000 cfs through turbines, 15,000
cfs through jet tubes and 276,000 cfs through spillways). The average siltation is 37,000 acre feet per year.
Historic Lake Level information showing the monthly levels since 1965 is available in a text file. Current levels and flows can be found at: