In this scenario, maybe: The pond is draining at full siphon (all air is out of the system) and you close the vent valve followed by the outlet valve (outlet valve should be after the trap, in your case after the last 45 deg. elbow you added) trapping water in the pipe. As long as no air can enter the system, it should start siphoning again when you open the outlet valve.
I would be concerned about shortening your siphon break vent too much. As you're siphoning, water is also being sucked in the vent pipe. If you shorten it too much, it could create a whirlpool, suck air and break the siphon prematurely. However, adding some sort of anivortex device may allow you to shorten it some.
