The lake dropped to a historic low of 681 feet mean sea level or just below the 5- percent capacity of the reservoir. Since the lake’s creation, it has experienced only six other occasions where the level dropped below 688.3 msl (75 percent full) occurring in 1971, 1974, 1978, 1984, 2011 and 2014.
Lake Granbury was completed in September 1969 and filled to capacity before the end of that year. Since that time, the lowest the lake has dropped was in 2014 when the level hit 681.47 msl; just over 11 feet below the top of the conservation pool. For a chart of historic lake levels, here.
The lake level dropped to its historic low level in 2014 for a number of reasons; some naturally occurring, some man-made. However, the reservoir would have been lower without the benefit of the water released from storage in Possum Kingdom Lake as a result of the Possum Kingdom-Granbury Water Management Study. These fluctuations in lake levels are typical for water supply lakes, as those levels respond to use, evaporation, inflows and rainfall.
Lake Granbury is permitted by the State of Texas and is an integral component for water supply in the State Water Plan. Like all water supply lakes, it was built to accumulate and store water during times of abundance for use when rainfall and river flows are inadequate to meet water needs.