In my solution (there are others, but it's the one I found when I made the puzzle), every single chain has the stream go up, right, and then down. The up part goes from the bottom block of the stack of greens all the way to the top. Then, it goes one block to the right. Finally, it goes all the way down to the bottom of the stack. The blocks above the ones that were aiming downward will be aimed upward to repeat the pattern for the next chain. When a chain clears, it will also adjust the next stack of blocks downward, but because the bottom block is pointing down, that block won't cause any harm. That adjustment does make it hard to visualize which blocks need to point up and which need to point down, but some trial and error should hopefully clear things up.
I can post a picture if this explanation is still too abstract. Good luck!
