Sanada Khumanthem

Guided bend river is hard to setup on daily basis, with that box setups everywhere, it didn't work in my case, i used like 9 bend nodes to make the box bend on my river, but later part on generating velocity, the bends distorted the particles mucb further, dont know why still Searching for solutions, i think is due to the volume and match size stuffs which I don't know about, anyone with solution?