Source : Webster's Revised Unabridged Dictionary (1913)

Lockage \Lock"age\, n.
   1. Materials for locks in a canal, or the works forming a
      lock or locks.

   2. Toll paid for passing the locks of a canal.

   3. Amount of elevation and descent made by the locks of a
      canal.

            The entire lock will be about fifty feet. --De Witt
                                                  Clinton.

Source : WordNet®

lockage
     n 1: a fee charged for passage through a lock in a canal or
          waterway
     2: a system of locks in a canal or waterway
     3: passage through a lock in a canal or waterway