The waters made him great, the deep set him up on high with her rivers running round about his plants, and sent out her little rivers unto all the trees of the field.
The waters made him great, the deep ... sent out her little rivers - the Tigris, with its branches and rivulets, or conduits for irrigation, was the source of Assyria's fertility. "The deep" is the ever-flowing water, never dry. Metaphorically, for Assyria's resources, as the 'conduits' are her colonies.