Source : Webster's Revised Unabridged Dictionary (1913)

Flowage \Flow"age\ (?; 48), n.
   An overflowing with water; also, the water which thus
   overflows.

Source : WordNet®

flowage
     n 1: gradual internal motion or deformation of a solid body (as
          by heat); "rock fracture and rock flowage are different
          types of geological deformation"
     2: a body of water that has been created by deliberately
        flooding an area; "many campsites were located near the
        flowage"
     3: the act of flooding; filling to overflowing [syn: {flood}]