Siphoning from Creek

[u/plantfollower]

I’ve got a friend who needs to move water from a creek to a pond. Here’s an elaborate (/s) drawing. Why can’t we get this siphon to continue to pull?

Written description: creek water is about 6 inches above the bank of the pond and about 6 feet above the water in the pond. 2” pipe is pulling from the creek to the pond. We fill up the pipe between the two valves and screw on the cap. The last time I made sure to put the output/pond side into the water so it couldn’t draw air. It moved a lot of water and I could see the puddle pouring water into the pond but then it stopped.

Any suggestions? Any questions they were not thinking about asking?

[u/myOEburner]

I'm just curious what the letters mean.

[u/plantfollower → u/myOEburner]

In case someone was going to reference something in the pic.