You can have a directed spray (maybe shot out of a giant fire hose at high pressure and flow), but without gravity, the liquid will disperse over a short distance. I don't see how that's avoidable because of entropy/diffusion. Gravity plus a container (river bed) create a perfect condition for the sorts of liquid flows we're accustomed to: a nearly identical acceleration on all particles, with a bounded displacement.

Just recreate the river bed from a solid material (to prevent dirt from floating away) and add a lid

if you have a laminar flow, wouldn't some equivalent of surface tension keep it together?