The 28,980-acre lake serves to fulfill a variety of local and regional needs. The primary purposes of the lake are flood control and water conservation. Associated purposes include fish and wildlife management and recreation. The operation of Lewisville Lake was modified in 1988 as part of the construction of Ray Roberts Lake, upstream of Lewisville Lake, resulting in a permanent increase of the conservation pool elevation from 515 feet msl to the current 522 feet msl.