Pison

Babylonian, the current, broad-flowing, one of the "four heads" into which the river which watered the garden of Eden was divided (Gen 2:11). Some identify it with the modern Phasis, others with the Halys, others the Jorak or Acampis, others the Jaab, the Indus, the Ganges, etc.

EBD - Easton's Bible Dictionary