I made this to test a timer system, and also for fun. It uses pistons to block off the water streams and then unblock them, causing the effect you see in the picture. the timer system is pretty simple, and you can see it in the pictures. I tried it with lava but I had problems with it falling to slow, so it never left the trenches.
Also, if you like this project, please comment, I love feedback and constructive criticism.